TW202323129A - Bicycle rear sprocket assembly and bicycle drive train - Google Patents

Abstract

A bicycle rear sprocket assembly is configured to be mounted to a sprocket support body of a bicycle rear hub assembly. The bicycle rear sprocket assembly comprises a plurality of bicycle sprockets. The plurality of bicycle sprockets comprises a first sprocket and a second sprocket. The first sprocket includes a first opening having a first minimum diameter that is smaller than a minimum outer diameter of the sprocket support body of the bicycle rear hub assembly. The second sprocket includes a second opening and at least ten internal spline teeth. The second opening has a second minimum diameter that is equal to or larger than the minimum outer diameter of the sprocket support body of the bicycle rear hub assembly. The at least ten internal spline teeth are configured to engage with the sprocket support body of the bicycle rear hub assembly.

Description

Bicycle rear sprocket assembly and bicycle transmission system

The invention relates to a bicycle rear sprocket assembly and a bicycle transmission system.

Cycling is becoming an increasingly popular form of recreation as well as a mode of transportation. Furthermore, cycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation, or competition, the bicycle industry is constantly improving the various components of the bicycle. One of the bicycle components that has been substantially redesigned is the sprocket assembly.

According to a first aspect of the present invention, a bicycle rear sprocket assembly is configured to be mounted to a sprocket support body of a bicycle rear hub assembly. The bicycle rear sprocket assembly includes a plurality of bicycle sprockets. The plurality of bicycle sprockets includes a first sprocket and a second sprocket. The first sprocket includes a first opening having a first minimum diameter that is smaller than a minimum outer diameter of the sprocket support body of the bicycle rear hub assembly. The second sprocket includes a second opening and at least ten inner spline teeth. The second opening has a second minimum diameter equal to or greater than the minimum outer diameter of the sprocket support body of the bicycle rear hub assembly. The at least ten internal spline teeth are configured to engage with the sprocket support body of the bicycle rear hub assembly. In the case of the bicycle rear sprocket assembly according to the first aspect, the first minimum diameter allows the first sprocket to have a smaller pitch circle diameter. This enables a wider gear range for the bicycle rear sprocket assembly. Furthermore, the at least ten internal spline teeth of the second sprocket reduce the rotational force applied to each of the at least ten internal spline teeth compared to a sprocket that includes nine or fewer internal spline teeth. This increases the durability of the second sprocket and/or increases the freedom of choice of the material of the second sprocket without reducing the durability of the second sprocket. According to a second aspect of the present invention, the bicycle rear sprocket assembly according to the first aspect further includes a locking member. The locking member includes a tubular body, an externally threaded portion, and a radial protrusion. The tubular body extends through the first opening of the first sprocket when the bicycle rear sprocket assembly is mounted to a state of the bicycle rear hub assembly. The tubular body includes a first axial end and a second axial end. The second axial end is opposite to the first axial end in an axial direction with respect to a rotation center axis of the bicycle rear sprocket assembly. In the state where the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly, the first axial end is positioned closer to an axial center of the bicycle rear hub assembly than the second axial end flat. The externally threaded portion is provided to the first axial end to fit within one of the sprocket support bodies of the bicycle rear hub assembly in the state in which the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly The threaded part engages. The radial protrusion extends radially outward from the second axial end with respect to the central axis of rotation to restrain the first chain in the state where the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly An axial movement of the wheel relative to the sprocket support body of the bicycle rear hub assembly. In the case of the bicycle rear sprocket assembly according to the second aspect, it is possible to mount a smaller sprocket to the bicycle rear hub assembly. This enables a wider gear range for the bicycle rear sprocket assembly. According to a third aspect of the present invention, the bicycle rear sprocket assembly according to the second aspect is configured such that the first sprocket includes a first inner side; Axially opposite to the first inner side. The radial protrusion is configured to abut the first sprocket in the first outward side. In the case of the bicycle rear sprocket assembly according to the third aspect, it is possible to mount smaller sprockets to the bicycle rear hub assembly. This enables a wider gear range for the bicycle rear sprocket assembly. According to a fourth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the third aspect is configured such that: the second sprocket is opposite to the bicycle rear chain A central axis of rotation of the wheel assembly is adjacent to the first sprocket in an axial direction without another sprocket between the first sprocket and the second sprocket. In the case of the bicycle rear sprocket assembly according to the fourth aspect, it is possible to mount smaller sprockets to the bicycle rear hub assembly. This enables a wider gear range for the bicycle rear sprocket assembly. According to a fifth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the fourth aspect is configured such that: the first sprocket includes a first and a first outward direction opposite to the first inward direction in an axial direction with respect to a central axis of rotation of the bicycle rear sprocket assembly. The first sprocket includes a first torque transmitting structure provided to the first inward side to directly or indirectly transmit a pedaling torque to the sprocket support body. In the case of the bicycle rear sprocket assembly according to the fifth aspect, it is possible to mount smaller sprockets to the bicycle rear hub assembly. This enables a wider gear range for the bicycle rear sprocket assembly. According to a sixth aspect of the present invention, the bicycle rear sprocket assembly according to the fifth aspect is configured such that: the first torque transmission structure includes at least ten first torque transmission teeth. In the case of the bicycle rear sprocket assembly according to the sixth aspect, the ten first torque-transmitting teeth of the first sprocket reduce the application to at least The rotational force of each of the ten first torque transmitting teeth. This increases the durability of the first sprocket and/or increases the freedom of choice of the material of the first sprocket without reducing the durability of the first sprocket. According to a seventh aspect of the present invention, the bicycle rear sprocket assembly according to the sixth aspect is configured such that the total number of one of the at least ten first torque transmitting teeth is equal to or greater than twenty. In the case of the bicycle rear sprocket assembly according to the seventh aspect, it is possible to improve the durability of the first sprocket. According to an eighth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the seventh aspect is configured such that: the at least ten inner sprockets of the second sprocket The total number of one of the spline teeth is equal to or greater than 20. In the case of the bicycle rear sprocket assembly according to the eighth aspect, it is possible to improve the durability of the second sprocket. According to a ninth aspect of the present invention, the bicycle rear sprocket assembly according to the eighth aspect is configured such that: the total number of the at least ten internal spline teeth of the second sprocket is equal to or greater than 28. In the case of the bicycle rear sprocket assembly according to the ninth aspect, it is possible to improve the durability of the second sprocket. According to a tenth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the ninth aspect is configured such that: the at least ten inner parts of the second sprocket The spline teeth have a first inner pitch angle and a second inner pitch angle different from the first inner pitch angle. In the case of the bicycle rear sprocket assembly according to the tenth aspect, it is possible to easily attach the bicycle rear sprocket assembly to the bicycle rear hub assembly in the correct circumferential position. According to an eleventh aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the tenth aspect is configured such that: the at least ten of the second sprockets At least one of the internal spline teeth has a first spline shape that is different from a second spline shape of the other of the at least ten internal spline teeth. In the case of the bicycle rear sprocket assembly according to the eleventh aspect, it is possible to easily attach the bicycle rear sprocket assembly to the bicycle rear hub assembly in the correct circumferential position. According to a twelfth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the eleventh aspect is configured such that: the at least ten of the second sprocket At least one of the internal spline teeth has a first spline size that is different from a second spline size of the other of the at least ten internal spline teeth. In the case of the bicycle rear sprocket assembly according to the twelfth aspect, it is possible to easily attach the bicycle rear sprocket assembly to the bicycle rear hub assembly in the correct circumferential position. According to a thirteenth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the twelfth aspect is configured such that: a total number of teeth of the first sprocket equal to or less than 10. In the case of the bicycle rear sprocket assembly according to the thirteenth aspect, it is possible to mount a smaller sprocket to the bicycle rear hub assembly. This enables a wider gear range for the bicycle rear sprocket assembly. According to a fourteenth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the thirteenth aspect is configured such that: the first sprocket is the bicycle rear The smallest sprocket in the sprocket assembly. In the case of the bicycle rear sprocket assembly according to the fourteenth aspect, it is possible to mount a smaller sprocket to the bicycle rear hub assembly. This enables a wider gear range for the bicycle rear sprocket assembly. According to a fifteenth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the fourteenth aspect further includes: a sprocket support member configured to At least ten internal spline teeth engage with the sprocket support body of the bicycle rear hub assembly. The plurality of bicycle sprockets includes an additional sprocket configured to attach to the sprocket support member. In the case of the bicycle rear sprocket assembly according to the fifteenth aspect, it is possible to reduce the weight of the bicycle rear sprocket assembly. According to a sixteenth aspect of the present invention, the bicycle rear sprocket assembly according to the fifteenth aspect is configured such that: the total number of teeth of one of the additional sprockets is equal to or greater than 46. In the case of the bicycle rear sprocket assembly according to the sixteenth aspect, the additional sprocket enables a wider gear range of the bicycle rear sprocket assembly. According to a seventeenth aspect of the present invention, the bicycle rear sprocket assembly according to the fifteenth aspect is configured such that: a total number of teeth of one of the additional sprockets is equal to or greater than 50. In the case of the bicycle rear sprocket assembly according to the seventeenth aspect, the additional sprocket enables a wider gear range of the bicycle rear sprocket assembly. According to an eighteenth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the seventeenth aspect is configured such that: the plurality of bicycle sprockets include the The second sprocket provides a plurality of second sprockets. Each of the plurality of second sprockets includes at least ten internal spline teeth configured to engage the sprocket support body of the bicycle rear hub assembly. In the case of the bicycle rear sprocket assembly according to the eighteenth aspect, it is possible to improve the durability of the plurality of second sprockets. According to a nineteenth aspect of the present invention, the bicycle rear sprocket assembly according to the eighteenth aspect further includes: a sprocket supporting member including the chain configured to be connected to the bicycle rear hub assembly The wheel supports at least ten internal spline teeth engaged by the main body. The plurality of bicycle sprockets includes an additional sprocket configured to attach to the sprocket support member. In the case of the bicycle rear sprocket assembly according to the nineteenth aspect, it is possible to reduce the weight of the bicycle rear sprocket assembly. According to a twentieth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the nineteenth aspect is configured such that: the total number of one of the plurality of bicycle sprockets Mesh is equal to or greater than 10. In the case of the bicycle rear sprocket assembly according to the twentieth aspect, it is possible to increase the speed level of the bicycle rear sprocket assembly. According to a twenty-first aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the twentieth aspect is configured such that: one of the plurality of bicycle sprockets The total number is equal to or greater than 11. In the case of the bicycle rear sprocket assembly according to the twenty-first aspect, it is possible to further increase the speed level of the bicycle rear sprocket assembly. According to a twenty-second aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the twenty-first aspect is configured such that: one of the plurality of bicycle sprockets A total number equal to or greater than 12. In the case of the bicycle rear sprocket assembly according to the twenty-second aspect, it is possible to further increase the speed level of the bicycle rear sprocket assembly. According to a twenty-third aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the twenty-second aspect is configured such that: the plurality of bicycle sprockets include One extra sprocket with a maximum tooth tip diameter. The at least ten internal spline teeth of the second sprocket have an internal spline top diameter. The ratio of the internal spline crown diameter to the maximum tooth tip diameter ranges from 0.15 to 0.18. In the case of the bicycle rear sprocket assembly according to the twenty-third aspect, it is possible to improve the durability of the second sprocket while realizing a wider gear range of the bicycle rear sprocket assembly. According to a twenty-fourth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the twenty-third aspect further includes an additional sprocket. The additional sprocket includes: at least one first shift facilitating region for facilitating a first shifting operation of a bicycle chain from the additional sprocket to an adjacent smaller sprocket; and at least one second a shift facilitating region for facilitating a second shift operation of the bicycle chain from the adjacent smaller sprocket to one of the additional sprockets. In the case of the bicycle rear sprocket assembly according to the twenty-fourth aspect, it is possible to smoothly perform the first shifting operation and the second shifting operation. According to a twenty-fifth aspect of the present invention, the bicycle rear sprocket assembly according to the second aspect or the third aspect is configured such that: the tubular body has a first sprocket equal to or less than 27 mm. outside diameter. In the case of the bicycle rear sprocket assembly according to the twenty-fifth aspect, it is possible to hold the bicycle rear sprocket assembly relative to the bicycle rear hub assembly by means of the locking member and achieve a wider bicycle rear sprocket assembly gear range. According to a twenty-sixth aspect of the present invention, the bicycle rear sprocket assembly according to the twenty-fifth aspect is configured such that: the first outer diameter is equal to or greater than 26 mm. In the case of the bicycle rear sprocket assembly according to the twenty-sixth aspect, it is possible to maintain or increase the strength of the locking member while realizing a wider gear range of the bicycle rear sprocket assembly. According to a twenty-seventh aspect of the present invention, the bicycle rear sprocket assembly according to the second aspect, the third aspect, the twenty-fifth aspect or the twenty-sixth aspect is configured Such that: the radial protrusion has a second outer diameter equal to or smaller than 32 mm. In the case of the bicycle rear sprocket assembly according to the twenty-seventh aspect, it is possible to hold the bicycle rear sprocket assembly with respect to the bicycle rear hub assembly by the locking member and to achieve a wider bicycle rear sprocket assembly gear range. According to a twenty-eighth aspect of the present invention, the bicycle rear sprocket assembly according to the twenty-seventh aspect is configured such that: the second outer diameter is equal to or greater than 30 mm. In the case of the bicycle rear sprocket assembly according to the twenty-eighth aspect, it is possible to maintain or increase the strength of the locking member while achieving a wider gear range of the bicycle rear sprocket assembly. According to a twenty-ninth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the second aspect, the third aspect, and the twenty-fifth to the twenty-eighth aspects is Configured such that: the locking member has a tool engaging portion. In the case of the bicycle rear sprocket assembly according to the twenty-ninth aspect, it is possible to easily attach the locking member by using the tool engaging portion. According to a thirtieth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the twenty-ninth aspect is configured such that: the plurality of bicycle sprockets serve as the A plurality of first sprockets provided as the first sprockets and a plurality of second sprockets provided as the second sprockets. Each of the plurality of first sprockets includes the first opening. Each of the plurality of second sprockets includes the second opening and the at least ten internal spline teeth configured to engage with the sprocket support body of the bicycle rear hub assembly. In the case of the bicycle rear sprocket assembly according to the thirtieth aspect, the plurality of first sprockets and the plurality of second sprockets enable a wider gear range of the bicycle rear sprocket assembly. According to a thirty-first aspect of the present invention, the bicycle rear sprocket assembly according to the fifteenth aspect is configured such that the additional sprocket is attached to the sprocket support member by an adhesive. In the case of the bicycle rear sprocket assembly according to the thirty-first aspect, since any metal fastener is not used, it is possible to further reduce the weight of the bicycle rear sprocket assembly. According to a thirty-second aspect of the present invention, the bicycle rear sprocket assembly according to the fifteenth aspect or the thirty-first aspect is configured such that: the sprocket supporting member is made of a resin material One of the non-metallic materials. In the case of the bicycle rear sprocket assembly according to the thirty-second aspect, it is possible to further reduce the weight of the bicycle rear sprocket assembly. According to a thirty-third aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the thirty-second aspect is configured such that: the second sprocket At least two of the at least ten internal spline teeth are circumferentially disposed at a first internal circumferential pitch angle relative to a central axis of rotation of the bicycle rear sprocket assembly. The first internal pitch angle ranges from 5 degrees to 36 degrees. In the case of the bicycle rear sprocket assembly according to the thirty-third aspect, it is possible to improve the durability of the second sprocket. According to a thirty-fourth aspect of the present invention, the bicycle rear sprocket assembly according to the thirty-third aspect is configured such that: the first inner circumferential pitch angle ranges from 10 degrees to 20 degrees. In the case of the bicycle rear sprocket assembly according to the thirty-fourth aspect, it is possible to further improve the durability of the second sprocket. According to a thirty-fifth aspect of the present invention, the bicycle rear sprocket assembly according to the thirty-fourth aspect is configured such that: the first inner circumferential pitch angle is equal to or smaller than 15 degrees. In the case of the bicycle rear sprocket assembly according to the thirty-fifth aspect, it is possible to further improve the durability of the second sprocket. According to a thirty-sixth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the thirty-third aspect to the thirty-fifth aspect is configured such that: the second sprocket At least two other internal spline teeth of the at least ten internal spline teeth are arranged along the circumference at a second internal circumferential pitch angle relative to the rotation central axis. The second inner circumferential pitch angle is different from the first inner circumferential pitch angle. In the case of the bicycle rear sprocket assembly according to the thirty-sixth aspect, it is possible to easily attach the bicycle rear sprocket assembly to the bicycle rear hub assembly in the correct circumferential position. According to a thirty-seventh aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the thirty-sixth aspect is configured such that: the second sprocket The at least ten internal spline teeth have an internal spline crown diameter equal to or less than 34 mm. In the case of the bicycle rear sprocket assembly according to the thirty-seventh aspect, it is possible to improve the durability of the second sprocket while realizing a wider gear range of the bicycle rear sprocket assembly. According to a thirty-eighth aspect of the present invention, the bicycle rear sprocket assembly according to the thirty-seventh aspect is configured such that: the inner spline top diameter of the second sprocket is equal to or smaller than 33 mm . In the case of the bicycle rear sprocket assembly according to the thirty-eighth aspect, it is possible to improve the durability of the second sprocket while realizing a wider gear range of the bicycle rear sprocket assembly. According to a thirty-ninth aspect of the present invention, the bicycle rear sprocket assembly according to the thirty-seventh aspect or the thirty-eighth aspect is configured such that: the inner sprocket of the second sprocket The key top diameter is equal to or greater than 29 mm. In the case of the bicycle rear sprocket assembly according to thirty-ninth, it is possible to improve the durability of the second sprocket. According to a fortieth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the thirty-ninth aspect is configured such that: the at least The ten internal spline teeth have an internal spline base diameter equal to or less than 32 mm. In the case of the bicycle rear sprocket assembly according to the fortieth aspect, the inner spline top diameter may increase the radial length of the drive surface of at least one inner spline tooth. This increases the strength of the second sprocket. According to a forty-first aspect of the present invention, the bicycle rear sprocket assembly according to the fortieth aspect is configured such that the internal spline bottom diameter is equal to or smaller than 31 mm. In the case of the bicycle rear sprocket assembly according to the forty-first aspect, the top diameter of the inner spline can further increase the radial length of the transmission surface of at least one inner spline tooth. This increases the strength of the second sprocket. According to a forty-second aspect of the present invention, the bicycle rear sprocket assembly according to the fortieth aspect or the forty-first aspect is configured such that: the internal spline bottom diameter is equal to or greater than 28 mm. In the case of the bicycle rear sprocket assembly according to the forty-second aspect, it is possible to obtain the necessary strength of the sprocket supporting body. According to a forty-third aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the forty-second aspect is configured such that: the at least ten internal splines The teeth include a plurality of internal splined drive surfaces for receiving drive rotational force from a rear hub assembly of the bicycle during pedaling. Each of the plurality of internal splined drive surfaces includes a radially outermost edge, a radially innermost edge, and a radial length defined from the radially outermost edge to the radially innermost edge. The sum of one of the radial lengths of the plurality of internal spline drive surfaces is equal to or greater than 7 mm. In the case of the bicycle rear sprocket assembly according to the forty-third aspect, it is possible to increase the radial length of the plurality of internal spline drive surfaces. This increases the strength of the second sprocket. According to a forty-fourth aspect of the present invention, the bicycle rear sprocket assembly according to the forty-third aspect is configured such that the sum of the radial lengths is equal to or greater than 10 mm. In the case of the bicycle rear sprocket assembly according to the forty-fourth aspect, it is possible to further increase the radial length of the plurality of internal spline drive surfaces. This increases the strength of the second sprocket. According to a forty-fifth aspect of the present invention, the bicycle rear sprocket assembly according to the forty-third aspect is configured such that: the sum of the radial lengths is equal to or greater than 15 mm. In the case of the bicycle rear sprocket assembly according to the forty-fifth aspect, it is possible to further increase the radial length of the plurality of internal spline drive surfaces. This increases the strength of the second sprocket. According to a forty-sixth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the forty-third aspect to the forty-fifth aspect is configured such that: This sum is equal to or less than 36 mm. In the case of the bicycle rear sprocket assembly according to the forty-sixth aspect, it is possible to further improve the productivity of the bicycle rear sprocket assembly. According to a forty-seventh aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the forty-sixth aspect is configured such that: the at least ten internal splines At least one of the teeth includes an internal splined surface having a first internal splined surface angle defined between the internal splined surface and a first radial line, the first radial line Extending from a central axis of rotation of the bicycle rear sprocket assembly to a radially outermost edge of the inner splined drive surface. The angle of the first inner spline surface ranges from 0° to 6°. In the case of the bicycle rear sprocket assembly according to the forty-seventh aspect, it is possible to increase the strength of the internal spline drive surface. According to a forty-eighth aspect of the present invention, the bicycle rear sprocket assembly according to the forty-seventh aspect is configured such that: the at least one of the at least ten internal spline teeth includes: a an internal splined non-drive surface having a second internal splined surface angle defined between the internal splined non-drive surface and a second radial line from the bicycle rear sprocket assembly The central axis of rotation extends to a radially outermost edge of the inner splined non-drive surface. The second internal spline surface angle ranges from 0° to 6°. In the case of the bicycle rear sprocket assembly according to the forty-eighth aspect, it is possible to increase the productivity of the bicycle rear sprocket assembly due to the symmetrical shape of the inner spline teeth. According to a forty-ninth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the forty-eighth aspect is configured such that: the second sprocket At least one of the at least ten internal spline teeth is circumferentially symmetrical with respect to a reference line extending in a radial direction relative to the rotational central axis from the rotational central axis to the at least ten internal splines A circumferential center point of the radially outermost end of the at least one of the teeth. In the case of the bicycle rear sprocket assembly according to the forty-ninth aspect, it is possible to improve the productivity of the bicycle rear sprocket assembly due to the symmetrical shape of the inner spline teeth. According to a fiftieth aspect of the present invention, a bicycle transmission system includes the bicycle rear sprocket assembly according to any one of the first aspect to the forty-ninth aspect and a bicycle rear hub assembly. The bicycle rear hub assembly comprises: a hub shaft including a shaft through hole having a minimum inner diameter equal to or greater than 13 mm; a hub body rotatable about a central axis of rotation of the bicycle rear hub assembly installed on the wheel hub shaft; and a sprocket supporting body, which is rotatably installed on the wheel hub shaft around the rotation center axis. In the case of the bicycle transmission system according to the fiftieth aspect, it is possible to increase the strength of the bicycle transmission system around the rear wheel while realizing a wider gear range of the bicycle rear sprocket assembly. According to a fifty-first aspect of the present invention, the bicycle rear sprocket assembly according to the fiftieth aspect is configured such that the minimum inner diameter of the shaft through hole is equal to or greater than 14 mm. In the case of the bicycle transmission system according to the fifty-first aspect, it is possible to further increase the strength of the bicycle transmission system around the rear wheel. According to a fifty-second aspect of the present invention, the bicycle rear sprocket assembly according to the fiftieth aspect or the fifty-first aspect is configured such that: the minimum inner diameter of the shaft through hole is equal to or less than 21 mm. In the case of the bicycle transmission system according to the fifty-second aspect, it is possible to increase the freedom of design of the bicycle rear hub assembly. According to a fifty-third aspect of the present invention, the bicycle rear sprocket assembly according to the sixth aspect is configured such that: the total number of the at least ten first torque transmission teeth ranges from 22 to 24 . In the case of the bicycle rear sprocket assembly according to the fifty-third aspect, the total number of at least ten first torque transmitting teeth improves the durability of the second sprocket while increasing the productivity of the bicycle rear sprocket assembly. According to a fifty-fourth aspect of the present invention, the bicycle rear sprocket assembly according to the first aspect is configured such that: a total number range of the at least ten internal spline teeth of the second sprocket Between 22 and 24. In the case of the bicycle rear sprocket assembly according to the fifty-fourth aspect, the total number of at least ten first torque transmitting teeth improves the durability of the second sprocket while improving the productivity of the bicycle rear sprocket assembly. According to a fifty-fifth aspect of the present invention, the bicycle rear sprocket assembly according to the thirty-third aspect is configured such that: the first inner circumferential pitch angle ranges from 13 degrees to 17 degrees. In the case of the bicycle rear sprocket assembly according to the fifty-fifth aspect, the first inner circumferential pitch angle improves the durability of the second sprocket while improving the productivity of the bicycle rear sprocket assembly. According to a fifty-sixth aspect of the present invention, the bicycle rear sprocket assembly according to the thirty-sixth aspect is configured such that: the second inner circumferential pitch angle ranges from 28 degrees to 32 degrees. In the case of the bicycle rear sprocket assembly according to the fifty-sixth aspect, it is possible to easily attach the bicycle rear sprocket assembly to the bicycle rear hub assembly in the correct circumferential position. According to a fifty-seventh aspect of the present invention, the bicycle rear sprocket assembly according to the thirty-sixth aspect is configured such that: the first inner circumferential pitch angle is half of the second inner circumferential pitch angle . In the case of the bicycle rear sprocket assembly according to the fifty-seventh aspect, it is possible to easily attach the bicycle rear sprocket assembly to the bicycle rear hub assembly in the correct circumferential position. According to a fifty-eighth aspect of the present invention, the bicycle rear sprocket assembly according to the forty-third aspect is configured such that: the radial lengths of the plurality of internal spline drive surfaces The sum ranges from 11 mm to 14 mm. In the case of the bicycle rear sprocket assembly according to the fifty-eighth aspect, the inner spline top diameter may increase the radial length of the drive surface of at least one inner spline tooth. This increases the strength of the second sprocket within the scope of increased productivity of the bicycle rear sprocket assembly.

Cross References to Related Applications This application is a continuation-in-part of U.S. Patent Application No. 15/712,388 filed September 22, 2017. The content of this application is incorporated herein by reference in its entirety. Embodiments will now be described with reference to the drawings, wherein like reference numerals designate corresponding or identical elements in the various views. Referring first to FIG. 1 , a bicycle transmission system 10 according to one embodiment includes a bicycle rear hub assembly 12 and a bicycle rear sprocket assembly 14 . The bicycle rear hub assembly 12 is fastened to the bicycle frame BF. The rear sprocket assembly 14 of the bicycle is installed on the rear wheel hub assembly 12 of the bicycle. The bicycle brake rotor 16 is installed on the rear hub assembly 12 of the bicycle. The bicycle transmission system 10 further includes a crank assembly 18 and a bicycle chain 20 . The crank assembly 18 includes a crankshaft 22 , a right crank arm 24 , a left crank arm 26 and a front sprocket 27 . Right crank arm 24 and left crank arm 26 are secured to crankshaft 22 . Front sprocket 27 is secured to at least one of crankshaft 22 and right crank arm 24 . The bicycle chain 20 meshes with the front sprocket 27 and the bicycle rear sprocket assembly 14 to transmit pedaling force from the front sprocket 27 to the bicycle rear sprocket assembly 14 . Crank assembly 18 includes front sprocket 27 as a single sprocket in the illustrated embodiment. However, crank assembly 18 may include a plurality of front sprockets. The bicycle rear sprocket assembly 14 is the rear sprocket assembly. However, the structure of the bicycle rear sprocket assembly 14 can be applied to the front sprocket. In this application, the following directional terms "front", "rear", "forward", "backward", "left", "right", "lateral", "upward" and "downward" and any other Similar directional terms refer to those directions determined based on a user (eg, rider) sitting on the saddle (not shown) of the bicycle and facing the handlebars (not shown). Accordingly, these terms, when used to describe the bicycle drivetrain 10, the bicycle rear hub assembly 12, or the bicycle rear sprocket assembly 14, shall be with respect to a bicycle drivetrain equipped as used in an upright riding position on a horizontal surface. 10. Interpret the bicycle of the bicycle rear wheel hub assembly 12 or the bicycle rear sprocket assembly 14. As seen in FIG. 2 , the bicycle rear hub assembly 12 and the bicycle rear sprocket assembly 14 have a central axis of rotation A1 . The bicycle rear sprocket assembly 14 is rotatably supported by the bicycle rear hub assembly 12 about a rotational center axis A1 relative to the bicycle frame BF ( FIG. 1 ). The bicycle rear sprocket assembly 14 is configured to engage a bicycle chain 20 to transmit a transmission rotational force F1 between the bicycle chain 20 and the bicycle rear sprocket assembly 14 during pedaling. During pedaling, the bicycle rear sprocket assembly 14 rotates about the rotation center axis A1 in the transmission rotation direction D11. The transmission rotation direction D11 is defined along the circumferential direction D1 of the bicycle rear hub assembly 12 or the bicycle rear sprocket assembly 14 . The counter-rotational direction D12 is the opposite direction of the drive rotation direction D11 and is defined along the circumferential direction D1. As seen in FIG. 2 , the bicycle rear hub assembly 12 includes a sprocket support body 28 . The bicycle rear sprocket assembly 14 is configured to mount to the sprocket support body 28 of the bicycle rear hub assembly 12 . The bicycle rear sprocket assembly 14 is mounted on the sprocket support body 28 to transmit the transmission rotational force F1 between the sprocket support body 28 and the bicycle rear sprocket assembly 14 . The bicycle rear hub assembly 12 includes a hub axle 30 . The sprocket supporting body 28 is rotatably mounted on the upper hub shaft 30 around the rotation center axis A1. The bicycle rear sprocket assembly 14 further includes a locking member 32 . The locking member 32 is secured to the sprocket support body 28 to retain the bicycle rear sprocket assembly 14 relative to the sprocket support body 28 in the axial direction D2 relative to the rotational center axis A1 . As seen in FIG. 3 , the bicycle rear hub assembly 12 is fastened to the bicycle frame BF by the wheel fastening structure WS. The hub shaft 30 includes a shaft through hole 30A. The fastening rod WS1 of the wheel fastening structure WS extends through the shaft through hole 30A of the hub shaft 30 . The hub shaft 30 includes a first shaft end 30B and a second shaft end 30C. The hub shaft 30 extends along the rotation center axis A1 between the first shaft end 30B and the second shaft end 30C. The first shaft end 30B is disposed in the first groove BF11 of the first frame BF1 of the bicycle frame BF. The second shaft end 30C is disposed in the second groove BF21 of the second frame BF2 of the bicycle frame BF. The hub axle 30 is held between the first frame BF1 and the second frame BF2 by the wheel fastening structure WS. The wheel fastening structure WS includes structures known in the applied bicycle. Therefore, for the sake of brevity, no detailed description will be given here. In this embodiment, the shaft through hole 30A has a minimum inner diameter BD1 equal to or greater than 13 mm. The minimum inner diameter BD1 of the shaft through hole 30A is preferably equal to or greater than 14 mm. The smallest inner diameter BD1 of the shaft through hole 30A is preferably equal to or smaller than 21 mm. In this embodiment, the minimum inner diameter BD1 of the shaft through hole 30A is 15 mm. However, the minimum inner diameter BD1 is not limited to this embodiment and the above range. The hub shaft 30 has a maximum outer diameter BD2 equal to or greater than 17 mm. The maximum outer diameter BD2 of the hub axle 30 is preferably equal to or greater than 20 mm. The maximum outer diameter BD2 of the hub axle 30 is preferably equal to or smaller than 23 mm. In this embodiment, the maximum outer diameter BD2 of the hub axle 30 is 21 mm. However, the maximum outer diameter BD2 of the hub axle 30 is not limited to this embodiment and the above range. The hub shaft 30 has a minimum outer diameter BD3 equal to or greater than 15 mm. The minimum outer diameter BD3 is preferably equal to or greater than 17 mm. The minimum outer diameter BD3 is preferably equal to or smaller than 19 mm. In this embodiment, the minimum outer diameter BD3 of the hub axle 30 is 17. 6mm. However, the minimum outer diameter BD3 is not limited to this embodiment and the above range. The hub shaft 30 includes a shaft tube 30X, a first shaft portion 30Y, and a second shaft portion 30Z. The shaft tube 30X has a tubular shape and extends along the rotation center axis A1. The first shaft portion 30Y is fastened to the first end of the shaft tube 30X. The second shaft portion 30Z is secured to the second end of the shaft tube 30X. At least one of the first shaft portion 30Y and the second shaft portion 30Z may be provided integrally with the shaft tube 30X. As seen in FIGS. 3 and 4 , the bicycle rear hub assembly 12 further includes a brake rotor support body 34 . The brake rotor supporting body 34 is rotatably mounted on the hub axle 30 around the rotation center axis A1. The brake rotor support body 34 is coupled to the bicycle brake rotor 16 ( FIG. 1 ) to transfer braking rotational force from the bicycle brake rotor 16 to the brake rotor support body 34 . As seen in FIG. 4 , the bicycle rear hub assembly 12 includes a hub body 36 . The hub main body 36 is rotatably mounted on the hub axle 30 around the rotation center axis A1 of the bicycle rear hub assembly 12 . In this embodiment, the sprocket support body 28 is a separate component from the hub body 36 . The brake rotor support body 34 is provided integrally with the hub body 36 as a one-piece unitary member. However, the sprocket support body 28 may be provided integrally with the hub body 36 . The brake rotor support body 34 may be a separate component from the hub body 36 . For example, the hub body 36 is made of a metal material including aluminum. As seen in FIG. 5 , the bicycle rear sprocket assembly 14 includes a plurality of bicycle sprockets. The plurality of bicycle sprockets includes a first sprocket and a second sprocket. In this embodiment, the plurality of bicycle sprockets includes the plurality of first sprockets SP1 and SP2 provided as the first sprockets. The plurality of bicycle sprockets also includes a plurality of second sprockets SP3 and SP4 provided as second sprockets. The plurality of bicycle sprockets includes additional sprockets. In this embodiment, the plurality of bicycle sprockets includes a plurality of additional sprockets SP5 to SP12. However, the total number of first sprockets is not limited to this embodiment. The total number of second sprockets is not limited to this embodiment. The total number of additional sprockets is not limited to this embodiment. Alternatively, the first sprockets SP1 and SP2 may be integrally formed as a single unitary member, with the first sprocket SP1 being a separate sprocket from the first sprocket SP2 in this embodiment. Similarly, the second sprockets SP3 and SP4 can be integrally formed as a single integral member, and the second sprocket SP3 is a separate sprocket from the second sprocket SP4 in this embodiment. For example, the total number of the plurality of bicycle sprockets is equal to or greater than ten. The total number of the plurality of bicycle sprockets may be equal to or greater than eleven. The total number of the plurality of bicycle sprockets may be equal to or greater than twelve. In this embodiment, the total number of the plurality of bicycle sprockets is twelve. However, the total number of the plurality of bicycle sprockets is not limited to this embodiment. For example, the total number of the plurality of bicycle sprockets can be 13, 14, or equal to or greater than 15. In this embodiment, the first sprocket SP1 is the smallest sprocket in the rear sprocket assembly 14 of the bicycle. The extra sprocket SP12 is the largest sprocket in the rear sprocket assembly 14 of the bicycle. The first sprocket SP2 corresponds to the high speed gear in the rear sprocket assembly 14 of the bicycle. The extra sprocket SP12 corresponds to the low gear in the rear sprocket assembly 14 of the bicycle. As seen in FIG. 5, the first sprocket SP1 has a pitch circle diameter PCD1. The first sprocket SP2 has a pitch circle diameter PCD2. The second sprocket SP3 has a pitch circle diameter PCD3. The second sprocket SP4 has a pitch circle diameter PCD4. The extra sprocket SP5 has a pitch circle diameter PCD5. The extra sprocket SP6 has a pitch circle diameter PCD6. The extra sprocket SP7 has a pitch circle diameter PCD7. The extra sprocket SP8 has a pitch circle diameter PCD8. The extra sprocket SP9 has a pitch circle diameter PCD9. The extra sprocket SP10 has a pitch circle diameter PCD10. The extra sprocket SP11 has a pitch circle diameter PCD11. The extra sprocket SP12 has a pitch circle diameter PCD12. The first sprocket SP1 has a pitch circle PC1 having a pitch circle diameter PCD1. The first sprocket SP2 has a pitch circle PC2 having a pitch circle diameter PCD2. The second sprocket SP3 has a pitch circle PC3 having a pitch circle diameter PCD3. The second sprocket SP4 has a pitch circle PC4 having a pitch circle diameter PCD4. The extra sprocket SP5 has a pitch circle PC5 with a pitch circle diameter PCD5. The extra sprocket SP6 has a pitch circle PC6 with a pitch circle diameter PCD6. The extra sprocket SP7 has a pitch circle PC7 with a pitch circle diameter PCD7. The extra sprocket SP8 has a pitch circle PC8 with a pitch circle diameter PCD8. The extra sprocket SP9 has a pitch circle PC9 with a pitch circle diameter PCD9. The extra sprocket SP10 has a pitch circle PC10 having a pitch circle diameter PCD10. The extra sprocket SP11 has a pitch circle PC11 having a pitch circle diameter PCD11. The extra sprocket SP12 has a pitch circle PC12 with a pitch circle diameter PCD12. The pitch circle PC1 of the first sprocket SP1 is defined by the central axis of the pin of the bicycle chain 20 ( FIG. 2 ) meshing with the first sprocket SP1 . The pitch circles PC2 to PC12 and the pitch circle PC1 are defined. Therefore, for the sake of brevity, no detailed description will be given here. In this embodiment, the pitch circle diameter PCD1 is smaller than the pitch circle diameter PCD2. The pitch circle diameter PCD2 is smaller than the pitch circle diameter PCD3. The pitch circle diameter PCD3 is smaller than the pitch circle diameter PCD4. The pitch circle diameter PCD4 is smaller than the pitch circle diameter PCD5. The pitch circle diameter PCD5 is smaller than the pitch circle diameter PCD6. The pitch circle diameter PCD6 is smaller than the pitch circle diameter PCD7. The pitch circle diameter PCD7 is smaller than the pitch circle diameter PCD8. The pitch circle diameter PCD8 is smaller than the pitch circle diameter PCD9. The pitch circle diameter PCD9 is smaller than the pitch circle diameter PCD10. The pitch circle diameter PCD10 is smaller than the pitch circle diameter PCD11. The pitch circle diameter PCD11 is smaller than the pitch circle diameter PCD12. The pitch circle diameter PCD1 is the smallest pitch circle diameter in the bicycle rear sprocket assembly 14 . The pitch circle diameter PCD12 is the largest pitch circle diameter in the bicycle rear sprocket assembly 14 . The first sprocket SP1 corresponds to the high speed gear in the rear sprocket assembly 14 of the bicycle. The extra sprocket SP12 corresponds to the low gear in the rear sprocket assembly 14 of the bicycle. However, the first sprocket SP1 may correspond to another gear in the bicycle rear sprocket assembly 14 . The extra sprocket SP12 may correspond to another gear in the bicycle rear sprocket assembly 14 . As seen in FIG. 6, the first sprocket SP2 is adjacent to the first sprocket SP1 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and between the first sprockets SP1 and SP2. There is no other sprocket. The second sprocket SP3 is adjacent to the first sprocket SP2 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and there is no other sprocket SP2 between the first sprocket SP2 and the second sprocket SP3. a sprocket. The second sprocket SP4 is adjacent to the second sprocket SP3 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and there is no other sprocket between the second sprocket SP3 and the second sprocket SP4. a sprocket. The first sprockets SP1 and SP2, the second sprocket SP3, the second sprocket SP4, and the additional sprockets SP5 to SP12 are arranged in this order in the axial direction D2. As seen in FIG. 7 , the first sprocket SP1 includes a sprocket body SP1A and a plurality of sprocket teeth SP1B. A plurality of sprocket teeth SP1B extend radially outward from the sprocket body SP1A relative to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . The total number of teeth of the first sprocket SP1 (the total number of teeth of at least one sprocket SP1B) is equal to or less than ten. In this embodiment, the total number of at least one sprocket tooth SP1B of the first sprocket SP1 is ten. However, the total number of the sprocket teeth SP1B of the first sprocket SP1 is not limited to this embodiment and the above scope. As seen in FIG. 8 , the first sprocket SP2 includes a sprocket body SP2A and a plurality of sprocket teeth SP2B. A plurality of sprocket teeth SP2B extend radially outward from the sprocket body SP2A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . In this embodiment, the total number of at least one sprocket SP2B is twelve. However, the total number of the sprocket teeth SP2B of the first sprocket SP2 is not limited to this embodiment. The first sprocket SP2 includes at least one first shift facilitating area SP2F1 to facilitate the first shifting operation of the bicycle chain 20 from the first sprocket SP2 to the first sprocket SP1 . The first sprocket SP2 includes at least one second shift facilitating area SP2F2 to facilitate the second shifting operation of the bicycle chain 20 from the first sprocket SP1 to the first sprocket SP2. In this embodiment, the first sprocket SP2 includes a plurality of first shift promoting areas SP2F1 for facilitating the first shift operation. The first sprocket SP2 includes a plurality of second shift promoting regions SP2F2 for facilitating the second shift operation. However, the total number of the first shift promoting regions SP2F1 is not limited to this embodiment. The total number of the second shift promoting regions SP2F2 is not limited to this embodiment. The term "displacement-facilitating region" as used herein is intended to be a region intentionally designed to facilitate the displacement operation of a bicycle chain from a sprocket to another axially adjacent sprocket in that region. In this embodiment, the first sprocket SP2 includes a plurality of first displacement promoting grooves SP2R1 for facilitating the first displacement operation. The first sprocket SP2 includes a plurality of second displacement promoting grooves SP2R2 for facilitating the second displacement operation. The first displacement promoting groove SP2R1 is disposed in the first displacement promoting region SP2F1. However, the first displacement promoting region SP2F1 may include another structure instead of or in addition to the first displacement promoting groove SP2R1. The second displacement promoting region SP2F2 may include another structure instead of or in addition to the second displacement promoting groove SP2R2. As seen in FIG. 9 , the second sprocket SP3 includes a sprocket body SP3A and a plurality of sprocket teeth SP3B. A plurality of sprocket teeth SP3B extend radially outward from the sprocket body SP3A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . In this embodiment, the total number of at least one sprocket SP3B is fourteen. However, the total number of sprocket teeth SP3B of the second sprocket SP3 is not limited to this embodiment. The second sprocket SP3 includes at least one first shift facilitating region SP3F1 to facilitate the first shifting operation of the bicycle chain 20 from the second sprocket SP3 to the first sprocket SP2 ( FIG. 6 ). The second sprocket SP3 includes at least one second displacement facilitating region SP3F2 to facilitate the second displacement operation of the bicycle chain 20 from the first sprocket SP2 ( FIG. 6 ) to the second sprocket SP3 . In this embodiment, the second sprocket SP3 includes a plurality of first shift promoting areas SP3F1 for facilitating the first shift operation. The second sprocket SP3 includes a plurality of second shift promoting regions SP3F2 for facilitating the second shift operation. However, the total number of the first shift promoting regions SP3F1 is not limited to this embodiment. The total number of the second shift promoting regions SP3F2 is not limited to this embodiment. In this embodiment, the second sprocket SP3 includes a plurality of first displacement promoting grooves SP3R1 for facilitating the first displacement operation. The second sprocket SP3 includes a plurality of second displacement promoting grooves SP3R2 for facilitating the second displacement operation. The first displacement promoting groove SP3R1 is disposed in the first displacement promoting region SP3F1. However, the first displacement promoting region SP3F1 may include another structure instead of or in addition to the first displacement promoting groove SP3R1. The second displacement promoting region SP3F2 may include another structure instead of or in addition to the second displacement promoting groove SP3R2. As seen in FIG. 10 , the second sprocket SP4 includes a sprocket body SP4A and a plurality of sprocket teeth SP4B. A plurality of sprocket teeth SP4B extend radially outward from the sprocket body SP4A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . In this embodiment, the total number of at least one sprocket SP4B is sixteen. However, the total number of the sprocket teeth SP4B of the second sprocket SP4 is not limited to this embodiment. The second sprocket SP4 includes at least one first shift facilitating area SP4F1 to facilitate the first shifting operation of the bicycle chain 20 from the second sprocket SP4 to the second sprocket SP3. The second sprocket SP4 includes at least one second shift facilitating area SP4F2 to facilitate the second shifting operation of the bicycle chain 20 from the second sprocket SP3 to the second sprocket SP4. In this embodiment, the second sprocket SP4 includes a plurality of first shift promoting areas SP4F1 for facilitating the first shift operation. The second sprocket SP4 includes a plurality of second shift promoting regions SP4F2 for facilitating the second shift operation. However, the total number of the first shift promoting regions SP4F1 is not limited to this embodiment. The total number of the second shift promoting regions SP4F2 is not limited to this embodiment. In this embodiment, the second sprocket SP4 includes a plurality of first displacement promoting grooves SP4R1 for facilitating the first displacement operation. The second sprocket SP4 includes a plurality of second displacement promoting grooves SP4R2 for facilitating the second displacement operation. The first displacement promoting groove SP4R1 is disposed in the first displacement promoting region SP4F1. However, the first displacement promoting region SP4F1 may include another structure instead of or in addition to the first displacement promoting groove SP4R1. The second displacement promoting region SP4F2 may include another structure instead of or in addition to the second displacement promoting groove SP4R2. As seen in FIG. 11 , the extra sprocket SP5 includes a sprocket body SP5A and a plurality of sprocket teeth SP5B. A plurality of sprocket teeth SP5B extend radially outward from the sprocket body SP5A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . In this embodiment, the total number of at least one sprocket SP5B is eighteen. However, the total number of sprocket teeth SP5B of the extra sprocket SP5 is not limited to this embodiment. The extra sprocket SP5 includes at least one first shift facilitating region SP5F1 to facilitate the first shifting operation of the bicycle chain 20 from the extra sprocket SP5 to the adjacent smaller sprocket SP4. The extra sprocket SP5 includes at least one second shift facilitating region SP5F2 to facilitate the second shifting operation of the bicycle chain 20 from the adjacent smaller sprocket SP4 to the extra sprocket SP5. The adjacent smaller sprocket SP4 is adjacent to the additional sprocket SP5 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and between the additional sprocket SP5 and the adjacent smaller sprocket SP4 There is no other sprocket. In this embodiment, the extra sprocket SP5 includes a plurality of first shift facilitating regions SP5F1 for facilitating the first shift operation. The extra sprocket SP5 includes a plurality of second shift promoting areas SP5F2 for facilitating the second shift operation. However, the total number of the first shift promoting regions SP5F1 is not limited to this embodiment. The total number of the second displacement promoting regions SP5F2 is not limited to this embodiment. In this embodiment, the extra sprocket SP5 includes a plurality of first shift-promoting grooves SP5R1 for facilitating the first shift operation. The extra sprocket SP5 includes a plurality of second displacement promoting grooves SP5R2 for facilitating the second displacement operation. The first displacement promoting groove SP5R1 is disposed in the first displacement promoting region SP5F1. The second displacement promoting groove SP5R2 is disposed in the second displacement promoting region SP5F2. However, the first displacement promoting region SP5F1 may include another structure instead of or in addition to the first displacement promoting groove SP5R1. The second displacement promoting region SP5F2 may include another structure instead of or in addition to the second displacement promoting groove SP5R2. As seen in FIG. 12, the extra sprocket SP6 includes a sprocket body SP6A and a plurality of sprocket teeth SP6B. A plurality of sprocket teeth SP6B extend radially outward from the sprocket body SP6A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . In this embodiment, the total number of at least one sprocket SP6B is twenty-one. However, the total number of sprocket teeth SP6B of the extra sprocket SP6 is not limited to this embodiment. The extra sprocket SP6 includes at least one first shift facilitating region SP6F1 to facilitate the first shifting operation of the bicycle chain 20 from the extra sprocket SP6 to the adjacent smaller sprocket SP5. The extra sprocket SP6 includes at least one second shift facilitating region SP6F2 to facilitate the second shifting operation of the bicycle chain 20 from the adjacent smaller sprocket SP5 to the extra sprocket SP6. The adjacent smaller sprocket SP5 is adjacent to the additional sprocket SP6 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and between the additional sprocket SP6 and the adjacent smaller sprocket SP5 There is no other sprocket. In this embodiment, the extra sprocket SP6 includes a plurality of first shift facilitating regions SP6F1 for facilitating the first shift operation. The extra sprocket SP6 includes a plurality of second shift promoting areas SP6F2 for facilitating the second shift operation. However, the total number of the first shift promoting regions SP6F1 is not limited to this embodiment. The total number of the second shift promoting regions SP6F2 is not limited to this embodiment. In this embodiment, the extra sprocket SP6 includes a plurality of first shift-promoting grooves SP6R1 for facilitating the first shift operation. The extra sprocket SP6 includes a plurality of second displacement promoting grooves SP6R2 for facilitating the second displacement operation. The first displacement promoting groove SP6R1 is placed in the first displacement promoting region SP6F1. The second displacement promoting groove SP6R2 is disposed in the second displacement promoting region SP6F2. However, the first displacement promoting region SP6F1 may include another structure instead of or in addition to the first displacement promoting groove SP6R1. The second displacement promoting region SP6F2 may include another structure instead of or in addition to the second displacement promoting groove SP6R2. As seen in FIG. 13, the extra sprocket SP7 includes a sprocket body SP7A and a plurality of sprocket teeth SP7B. A plurality of sprocket teeth SP7B extend radially outward from the sprocket body SP7A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . In this embodiment, the total number of at least one sprocket SP7B is twenty-four. However, the total number of sprocket teeth SP7B of the extra sprocket SP7 is not limited to this embodiment. The extra sprocket SP7 includes at least one first shift facilitating region SP7F1 to facilitate the first shifting operation of the bicycle chain 20 from the extra sprocket SP7 to the adjacent smaller sprocket SP6. The extra sprocket SP7 includes at least one second shift facilitating region SP7F2 to facilitate the second shifting operation of the bicycle chain 20 from the adjacent smaller sprocket SP6 to the extra sprocket SP7. The adjacent smaller sprocket SP6 is adjacent to the additional sprocket SP7 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and between the additional sprocket SP7 and the adjacent smaller sprocket SP6 There is no other sprocket. In this embodiment, the extra sprocket SP7 includes a plurality of first shift facilitating regions SP7F1 for facilitating the first shift operation. The extra sprocket SP7 includes a plurality of second shift promoting areas SP7F2 for facilitating the second shift operation. However, the total number of the first shift promoting regions SP7F1 is not limited to this embodiment. The total number of the second shift promoting regions SP7F2 is not limited to this embodiment. In this embodiment, the extra sprocket SP7 includes a plurality of first shift-promoting grooves SP7R1 for facilitating the first shift operation. The extra sprocket SP7 includes a plurality of second displacement promoting grooves SP7R2 for facilitating the second displacement operation. The first displacement promoting groove SP7R1 is placed in the first displacement promoting region SP7F1. The second displacement promoting groove SP7R2 is disposed in the second displacement promoting region SP7F2. However, the first displacement promoting region SP7F1 may include another structure instead of or in addition to the first displacement promoting groove SP7R1. The second displacement promoting region SP7F2 may include another structure instead of or in addition to the second displacement promoting groove SP7R2. As seen in FIG. 14, the extra sprocket SP8 includes a sprocket body SP8A and a plurality of sprocket teeth SP8B. A plurality of sprocket teeth SP8B extend radially outward from the sprocket body SP8A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . In this embodiment, the total number of at least one sprocket SP8B is twenty-eight. However, the total number of sprocket teeth SP8B of the extra sprocket SP8 is not limited to this embodiment. The extra sprocket SP8 includes at least one first shift facilitating region SP8F1 to facilitate the first shifting operation of the bicycle chain 20 from the extra sprocket SP8 to the adjacent smaller sprocket SP7. The extra sprocket SP8 includes at least one second shift facilitating region SP8F2 to facilitate the second shifting operation of the bicycle chain 20 from the adjacent smaller sprocket SP7 to the extra sprocket SP8. The adjacent smaller sprocket SP7 is adjacent to the additional sprocket SP8 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and between the additional sprocket SP8 and the adjacent smaller sprocket SP7 There is no other sprocket. In this embodiment, the extra sprocket SP8 includes a plurality of first shift facilitating regions SP8F1 for facilitating the first shift operation. The extra sprocket SP8 includes a plurality of second shift facilitating areas SP8F2 for facilitating the second shift operation. However, the total number of the first shift promoting regions SP8F1 is not limited to this embodiment. The total number of the second shift promoting regions SP8F2 is not limited to this embodiment. In this embodiment, the extra sprocket SP8 includes a plurality of first shift-promoting grooves SP8R1 for facilitating the first shift operation. The extra sprocket SP8 includes a plurality of second shift-promoting grooves SP8R2 for facilitating the second shift operation. The first displacement promoting groove SP8R1 is placed in the first displacement promoting region SP8F1. The second displacement promoting groove SP8R2 is disposed in the second displacement promoting region SP8F2. However, the first displacement promoting region SP8F1 may include another structure instead of or in addition to the first displacement promoting groove SP8R1. The second displacement promoting region SP8F2 may include another structure instead of or supplementing the second displacement promoting groove SP8R2. As seen in Fig. 15, the extra sprocket SP9 includes a sprocket body SP9A and a plurality of sprocket teeth SP9B. A plurality of sprocket teeth SP9B extend radially outward from the sprocket body SP9A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . In this embodiment, the total number of at least one sprocket SP9B is thirty-three. However, the total number of sprocket teeth SP9B of the extra sprocket SP9 is not limited to this embodiment. The extra sprocket SP9 includes at least one first shift facilitating region SP9F1 to facilitate the first shifting operation of the bicycle chain 20 from the extra sprocket SP9 to the adjacent smaller sprocket SP8. The extra sprocket SP9 includes at least one second shift facilitating region SP9F2 to facilitate the second shifting operation of the bicycle chain 20 from the adjacent smaller sprocket SP8 to the extra sprocket SP9. The adjacent smaller sprocket SP8 is adjacent to the additional sprocket SP9 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and between the additional sprocket SP9 and the adjacent smaller sprocket SP8 There is no other sprocket. In this embodiment, the extra sprocket SP9 includes a plurality of first shift facilitating regions SP9F1 for facilitating the first shift operation. The extra sprocket SP9 includes a plurality of second shift facilitating areas SP9F2 for facilitating the second shift operation. However, the total number of the first shift promoting regions SP9F1 is not limited to this embodiment. The total number of the second displacement promoting regions SP9F2 is not limited to this embodiment. In this embodiment, the extra sprocket SP9 includes a plurality of first shift-promoting grooves SP9R1 for facilitating the first shift operation. The extra sprocket SP9 includes a plurality of second shift-promoting grooves SP9R2 for facilitating the second shift operation. The first displacement promoting groove SP9R1 is placed in the first displacement promoting region SP9F1. The second displacement promoting groove SP9R2 is disposed in the second displacement promoting region SP9F2. However, the first displacement promoting region SP9F1 may include another structure instead of or in addition to the first displacement promoting groove SP9R1. The second displacement promoting region SP9F2 may include another structure instead of or in addition to the second displacement promoting groove SP9R2. As seen in FIG. 16 , the extra sprocket SP10 includes a sprocket body SP10A and a plurality of sprocket teeth SP10B. A plurality of sprocket teeth SP10B extend radially outward from the sprocket main body SP10A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . In this embodiment, the total number of at least one sprocket SP10B is thirty-nine. However, the total number of sprocket teeth SP10B of the extra sprocket SP10 is not limited to this embodiment. The extra sprocket SP10 includes at least one first shift facilitating region SP10F1 to facilitate the first shifting operation of the bicycle chain 20 from the extra sprocket SP10 to the adjacent smaller sprocket SP9. The extra sprocket SP10 includes at least one second shift facilitating region SP10F2 to facilitate the second shifting operation of the bicycle chain 20 from the adjacent smaller sprocket SP9 to the extra sprocket SP10. The adjacent smaller sprocket SP9 is adjacent to the additional sprocket SP10 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and between the additional sprocket SP10 and the adjacent smaller sprocket SP9 There is no other sprocket. In this embodiment, the extra sprocket SP10 includes a plurality of first shift facilitating regions SP10F1 for facilitating the first shift operation. The extra sprocket SP10 includes a plurality of second shift facilitating regions SP10F2 for facilitating the second shift operation. However, the total number of the first shift promoting regions SP10F1 is not limited to this embodiment. The total number of the second shift promoting regions SP10F2 is not limited to this embodiment. In this embodiment, the extra sprocket SP10 includes a plurality of first shift-promoting grooves SP10R1 for facilitating the first shift operation. The extra sprocket SP10 includes a plurality of second shift-promoting grooves SP10R2 for facilitating the second shift operation. The first displacement promoting groove SP10R1 is disposed in the first displacement promoting region SP10F1. The second displacement promoting groove SP10R2 is disposed in the second displacement promoting region SP10F2. However, the first displacement promoting region SP10F1 may include another structure instead of or in addition to the first displacement promoting groove SP10R1. The second displacement promoting region SP10F2 may include another structure instead of or in addition to the second displacement promoting groove SP10R2. As seen in FIG. 17 , the extra sprocket SP11 includes a sprocket body SP11A and a plurality of sprocket teeth SP11B. A plurality of sprocket teeth SP11B extend radially outward from the sprocket main body SP11A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . In this embodiment, the total number of at least one sprocket SP11B is 45. However, the total number of sprocket teeth SP11B of the extra sprocket SP11 is not limited to this embodiment. The extra sprocket SP11 includes at least one first shift facilitating region SP11F1 to facilitate the first shifting operation of the bicycle chain 20 from the extra sprocket SP11 to the adjacent smaller sprocket SP10. The extra sprocket SP11 includes at least one second shift facilitating region SP11F2 to facilitate the second shifting operation of the bicycle chain 20 from the adjacent smaller sprocket SP10 to the extra sprocket SP11. The adjacent smaller sprocket SP10 is adjacent to the additional sprocket SP11 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and between the additional sprocket SP11 and the adjacent smaller sprocket SP10 There is no other sprocket. In this embodiment, the extra sprocket SP11 includes a plurality of first shift facilitating regions SP11F1 for facilitating the first shift operation. The extra sprocket SP11 includes a plurality of second shift-promoting groove areas SP11F2 for facilitating the second shift operation. However, the total number of the first shift promoting regions SP11F1 is not limited to this embodiment. The total number of the second displacement promoting regions SP11F2 is not limited to this embodiment. In this embodiment, the extra sprocket SP11 includes a plurality of first displacement promoting grooves SP11R1 for facilitating the first displacement operation. The extra sprocket SP11 includes a plurality of second displacement promoting grooves SP11R2 for facilitating the second displacement operation. The first displacement promoting groove SP11R1 is disposed in the first displacement promoting region SP11F1. The second displacement promoting groove SP11R2 is disposed in the second displacement promoting region SP11F2. However, the first displacement promoting region SP11F1 may include another structure instead of or in addition to the first displacement promoting groove SP11R1. The second displacement promoting region SP11F2 may include another structure instead of or in addition to the second displacement promoting groove SP11R2. As seen in FIG. 18, the extra sprocket SP12 includes a sprocket body SP12A and a plurality of sprocket teeth SP12B. A plurality of sprocket teeth SP12B extend radially outward from the sprocket main body SP12A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . The total number of teeth of the extra sprocket SP12 is equal to or greater than 46. The total number of teeth of the extra sprocket SP12 can also be equal to or greater than 50. The total number of teeth of the additional sprocket SP12 is 51 in this embodiment. However, the total number of at least one sprocket tooth SP12B of the additional sprocket SP12 is not limited to this embodiment and the above scope. The extra sprocket SP12 includes at least one first shift facilitating region SP12F1 to facilitate the first shifting operation of the bicycle chain 20 from the extra sprocket SP12 to the adjacent smaller sprocket SP11. The extra sprocket SP12 includes at least one second shift facilitating region SP12F2 to facilitate the second shifting operation of the bicycle chain 20 from the adjacent smaller sprocket SP11 to the extra sprocket SP12. The adjacent smaller sprocket SP11 is adjacent to the additional sprocket SP12 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and between the additional sprocket SP12 and the adjacent smaller sprocket SP11 There is no other sprocket. In this embodiment, the extra sprocket SP12 includes a plurality of first shift facilitating regions SP12F1 for facilitating the first shift operation. The extra sprocket SP12 includes a plurality of second shift promoting regions SP12F2 for facilitating the second shift operation. However, the total number of the first shift promoting regions SP12F1 is not limited to this embodiment. The total number of the second shift promoting regions SP12F2 is not limited to this embodiment. In this embodiment, the extra sprocket SP12 includes a plurality of first shift promoting grooves SP12R1 for facilitating the first shift operation. The extra sprocket SP12 includes a plurality of second displacement promoting grooves SP12R2 for facilitating the second displacement operation. The first displacement promoting groove SP12R1 is disposed in the first displacement promoting region SP12F1. The second displacement promoting groove SP12R2 is disposed in the second displacement promoting region SP12F2. However, the first displacement promoting region SP12F1 may include another structure instead of or in addition to the first displacement promoting groove SP12R1. The second displacement promoting region SP12F2 may include another structure instead of or in addition to the second displacement promoting groove SP12R2. As seen in FIG. 19, the sprockets SP1 to SP12 are separate members from each other. However, at least one of the sprockets SP1 to SP12 may be at least partially integrally provided with another one of the sprockets SP1 to SP12. All sprockets SP1 to SP12 may be integrally formed with each other as a one-piece integral unit. In this case, at least one of the sprockets SP3-SP12 may include at least ten internal spline teeth. The bicycle rear sprocket assembly 14 further includes a sprocket support member 37, a plurality of spacers 38, a first ring 39A and a second ring 39B. The first ring 39A is disposed between the second sprocket SP3 and the second sprocket SP4 in the axial direction D2. The second ring 39B is disposed between the second sprocket SP4 and the additional sprocket SP5 in the axial direction D2. The additional sprocket is configured for attachment to the sprocket support member 37 . The additional sprockets SP5 to SP12 are configured in this embodiment for attachment to the sprocket support member 37 . As seen in FIG. 6 , the additional sprocket is attached to the sprocket support member 37 by adhesive 37A, for example. In this embodiment, the additional sprockets SP5 to SP12 are attached to the sprocket support member 37 by an adhesive 37A. Therefore, it is possible to reduce the weight of the bicycle rear sprocket assembly 14 by reducing or eliminating metal fasteners. However, at least one of the additional sprockets SP5-SP12 may be attached to the sprocket support member 37 by another structure other than the adhesive 37A, including metal fasteners. At least one of the additional sprockets SP5 to SP12 can be engaged with the sprocket support body 28 without the sprocket support member 37 . The sprocket support member 37 may be omitted from the bicycle rear sprocket assembly 14 . In addition, at least one of the second sprockets SP3 and SP4 may be attached to the sprocket support member 37 . As seen in FIG. 4, the locking member 32 includes a tubular body 32A, an externally threaded portion 32B, and a radial protrusion 32C. The tubular body 32A includes a first axial end 32D and a second axial end 32E. With respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 , the second axial end 32E is opposite to the first axial end 32D in the axial direction D2 . As seen in FIG. 6, with the bicycle rear sprocket assembly 14 mounted to the bicycle rear hub assembly 12, the first axial end 32D is positioned closer to the bicycle rear hub assembly 12 than the second axial end 32E The axial center plane CPL. The axial center plane CPL is perpendicular to the rotation center axis A1. As seen in FIG. 3 , the axial center plane CPL is defined to bisect the axial length of the rear bicycle hub assembly 12 in the axial direction D2 . As seen in FIG. 6, an externally threaded portion 32B is provided to the first axial end 32D for sprocket support with the bicycle rear hub assembly 12 in a state where the bicycle rear sprocket assembly 14 is mounted to the bicycle rear hub assembly 12. The internally threaded portion 28A of the main body 28 engages. The radial protrusion 32C extends radially outward from the second axial end 32E with respect to the rotation center axis A1 to restrain the first sprocket SP2 in a state where the bicycle rear sprocket assembly 14 is mounted to the bicycle rear hub assembly 12 Axial movement of the sprocket support body 28 relative to the bicycle rear hub assembly 12 . The first sprocket SP1 includes a first inner SP1G and a first outer SP1H. The first outward SP1H is opposed to the first inner SP1G in the axial direction D2. The radial protrusion 32C is configured to abut the first sprocket SP1 in the first outward side SP1H. The first sprockets SP1 and SP2 are arranged between the radial protrusion 32C and the second sprocket SP3 in the axial direction. The first sprockets SP1 and SP2 , the second sprocket SP3 , the second sprocket SP4 and the first ring 39A are held between the radial protrusion 32C and the sprocket support member 37 in the axial direction D2 . As seen in FIG. 4 , the locking member 32 has a tool engaging portion 32F. A tool engaging portion 32F is provided on an inner peripheral surface 32A1 of the tubular body 32A to engage with a fastening tool (not shown). In this embodiment, the tool engaging portion 32F includes a plurality of engaging grooves 32G that will be used when the locking member 32 is threadedly attached to the sprocket support body 28 by the externally threaded portion 32B and the internally threaded portion 28A. Engage with fastening tool. As seen in FIGS. 20 and 21 , the sprocket support body 28 includes at least one external spline tooth 40 configured to engage the bicycle rear sprocket assembly 14 ( FIG. 6 ). The sprocket support body 28 includes at least ten external spline teeth 40 configured to mesh with the bicycle rear sprocket assembly 14 ( FIG. 6 ). That is, at least one external spline tooth 40 includes a plurality of external spline teeth 40 . The sprocket support body 28 includes a base support 41 having a tubular shape. The base support 41 extends along the rotation center axis A1. External spline teeth 40 extend radially outward from base support 41 . The sprocket support body 28 includes a larger diameter portion 42 , a flange 44 and a plurality of helical outer spline teeth 46 . The larger diameter portion 42 and the flange 44 extend radially outward from the base support 41 . The larger diameter portion 42 is disposed between the plurality of outer spline teeth 40 and the flange 44 in the axial direction D2. The larger diameter portion 42 and the flange 44 are disposed between the plurality of outer spline teeth 40 and the plurality of helical outer spline teeth 46 in the axial direction D2. As seen in FIG. 6 , the bicycle rear sprocket assembly 14 is held between the larger diameter portion 42 and the radial protrusion 32C of the locking member 32 in the axial direction D2 . The larger diameter portion 42 may have an internal cavity such that a transmission structure, such as a one-way coupling, may be accommodated within the internal cavity. The larger diameter portion 42 can be omitted from the bicycle rear hub assembly 12 as desired. As seen in Figure 22, at least one of the at least ten outer spline teeth 40 has an axial spline tooth length SL1. Each of the external spline teeth 40 has an axial spline tooth length SL1. The axial spline tooth length SL1 is equal to or less than 27 mm. The axial spline tooth length SL1 is equal to or greater than 22 mm. In this embodiment, the axial spline tooth length SL1 is 24. 9 mm. However, the axial spline tooth length SL1 is not limited to this embodiment and the above range. As seen in FIG. 23 , the total number of at least ten external spline teeth 40 is equal to or greater than twenty. The total number of at least ten external spline teeth 40 is preferably equal to or greater than twenty-five. The total number of at least ten external spline teeth 40 is preferably equal to or greater than twenty-eight. The total number of external spline teeth 40 is preferably equal to or less than seventy-two. In this embodiment, the total number of external spline teeth 40 is twenty-nine. However, the total number of external spline teeth 40 is not limited to this embodiment and the above range. At least ten outer spline teeth 40 have a first outer circumferential pitch angle PA11 and a second outer circumferential pitch angle PA12. At least two of the at least ten external spline teeth 40 are circumferentially arranged at a first external circumferential pitch angle PA11 with respect to the rotation central axis A1. In other words, at least two of the plurality of external spline teeth 40 are arranged along the circumference at the first external pitch angle PA11 with respect to the rotation center axis A1 of the bicycle rear hub assembly 12 . At least two of the at least ten external spline teeth 40 are arranged along the circumference at a second external pitch angle PA12 with respect to the rotation center axis A1 of the bicycle rear hub assembly 12 . In other words, at least two of the plurality of external spline teeth 40 are arranged along the circumference at the second external peripheral pitch angle PA12 with respect to the rotation center axis A1 of the bicycle rear hub assembly 12 . In this embodiment, the second outer pitch angle PA12 is different from the first outer pitch angle PA11. However, the second outer pitch angle PA12 may be substantially equal to the first outer pitch angle PA11. In this embodiment, the external spline teeth 40 are arranged at a first external pitch angle PA11 in the circumferential direction D1. Two of the external spline teeth 40 are arranged at a second external pitch angle PA12 in the circumferential direction D1. However, at least two of the outer spline teeth 40 may be arranged at another outer circumferential pitch angle in the circumferential direction D1. The first outer pitch angle PA11 ranges from 5 degrees to 36 degrees. The first outer pitch angle PA11 preferably ranges from 10 degrees to 20 degrees. The first outer peripheral pitch angle PA11 is preferably equal to or smaller than 15 degrees. In this embodiment, the first outer pitch angle PA11 is 12 degrees. However, the first outer pitch angle PA11 is not limited to this embodiment and the above range. The second outer pitch angle PA12 ranges from 5 degrees to 36 degrees. In this embodiment, the second outer peripheral pitch angle PA12 is 24 degrees. However, the second outer peripheral pitch angle PA12 is not limited to this embodiment and the above range. At least one of the external spline teeth 40 may be different from the first spline shape of the second spline shape of the other of the external spline teeth 40 . At least one of the at least ten external spline teeth 40 may have a first spline size that is different from a second spline size of another of the at least ten external spline teeth 40 . At least one of the external spline teeth 40 has a different profile than the other of the external spline teeth 40 when viewed along the rotational center axis A1 . In this embodiment, the outer spline teeth 40X have a first spline shape that is different from the second spline shape of the other of the outer spline teeth 40 . The outer spline teeth 40X have a first spline size that is different from the second spline size of the other of the outer spline teeth 40 . However, as seen in Fig. 24, at least ten outer spline teeth 40 may have the same spline shape as each other. At least ten external spline teeth 40 may have the same spline size as one another. At least ten external spline teeth 40 may have the same profile as each other. As seen in FIG. 25 , each of the at least ten external spline teeth 40 has an external spline drive surface 48 and an external spline non-drive surface 50 . The plurality of external spline teeth 40 includes a plurality of external spline drive surfaces 48 for receiving the drive rotational force F1 from the bicycle rear sprocket assembly 14 ( FIG. 6 ) during pedaling. The plurality of external spline teeth 40 includes a plurality of external spline non-drive surfaces 50 . The external splined drive surface 48 can contact the bicycle rear sprocket assembly 14 to receive the drive rotational force F1 from the bicycle rear sprocket assembly 14 ( FIG. 6 ) during pedaling. The external spline drive surface 48 faces in the counter-rotational direction D12. The outer splined surface 48 faces the inner splined surface 66 of the bicycle rear sprocket assembly 14 when the bicycle rear sprocket assembly 14 is mounted to the bicycle rear hub assembly 12 . The external spline non-transmission surface 50 is disposed on the opposite side of the external spline transmission surface 48 in the circumferential direction D1. The external splined non-drive surface 50 faces the drive rotation direction D11 so as not to receive the drive rotation force F1 from the bicycle rear sprocket assembly 14 during pedaling. The outer splined non-drive surface 50 faces the inner splined non-drive surface 68 of the bicycle rear sprocket assembly 14 in a state where the bicycle rear sprocket assembly 14 is mounted to the bicycle rear hub assembly 12 . At least ten external spline teeth 40 each have a circumferential maximum width MW1. The outer spline teeth 40 each have a maximum circumferential width MW1. The circumferential maximum width MW1 is defined as the maximum width receiving the thrust F2 applied to the external spline teeth 40 . The circumferential maximum width MW1 is defined as the linear distance based on the external spline drive surface 48 . The plurality of outer splined drive surfaces 48 each include a radially outermost edge 48A and a radially innermost edge 48B. The outer splined drive surface 48 extends from a radially outermost edge 48A to a radially innermost edge 48B. The first reference circle RC11 is defined on the radially innermost edge 48B and centered on the rotation central axis A1. The first reference circle RC11 intersects the outer splined non-drive surface 50 at a reference point 50R. The circumferential maximum width MW1 extends linearly from the radially innermost edge 48B to the reference point 50R in the circumferential direction D1. The plurality of external splined non-drive surfaces 50 each include a radially outermost edge 50A and a radially innermost edge 50B. The outer splined non-drive surface 50 extends from a radially outermost edge 50A to a radially innermost edge 50B. In this embodiment, the reference point 50R coincides with the radially innermost edge 50B. However, the reference point 50R may be offset from the radially innermost edge 50B. The sum of the maximum circumferential widths MW1 is equal to or greater than 55 mm. The sum of the circumferential maximum widths MW1 is preferably equal to or greater than 60 mm. The sum of the circumferential maximum widths MW1 is preferably equal to or less than 70 mm. In this embodiment, the sum of the maximum circumferential width MW1 is 60. 1 mm. However, the sum of the maximum circumferential widths MW1 is not limited to this embodiment and the above range. As seen in FIG. 26, at least one external spline tooth 40 has an external spline top diameter DM11 equal to or smaller than 34 mm. External spline top diameter DM11 is equal to or less than 33 mm. External spline top diameter DM11 is equal to or greater than 29 mm. In this embodiment, the external spline top diameter DM11 is 32. 6 mm. However, the external spline top diameter DM11 is not limited to this embodiment and the above range. At least one external spline tooth 40 has an external spline base diameter DM12. At least one external spline tooth 40 has an external spline root circle RC12 having an external spline base diameter DM12. However, the outer spline root circle RC12 may have another diameter than the outer spline bottom diameter DM12. External spline bottom diameter DM12 is equal to or less than 32 mm. External spline bottom diameter DM12 is equal to or less than 31 mm. External spline bottom diameter DM12 is equal to or greater than 28 mm. In this embodiment, the external spline bottom diameter DM12 is 30. 2 mm. However, the external spline bottom diameter DM12 is not limited to this embodiment and the above range. The larger diameter portion 42 has an outer diameter DM13 that is larger than the outer spline top diameter DM11. The outer diameter DM13 ranges from 32 mm to 40 mm. In this embodiment, the outer diameter DM13 is 35 mm. However, the outer diameter DM13 is not limited to this embodiment. As seen in FIG. 25 , the plurality of outer splined drive surfaces 48 each include a radial length RL11 defined from a radially outermost edge 48A to a radially innermost edge 48B. The sum of the radial lengths RL11 of the plurality of external spline transmission surfaces 48 is equal to or greater than 7 mm. The sum of the radial lengths RL11 is equal to or greater than 10 mm. The sum of the radial lengths RL11 is equal to or greater than 15 mm. The sum of the radial lengths RL11 is equal to or less than 36 mm. In this embodiment, the sum of the radial lengths RL11 is 16. 6mm. However, the sum of the radial lengths RL11 is not limited to this embodiment. The plurality of external spline teeth 40 has an additional radial length RL12. The additional radial lengths RL12 are respectively defined from the outer spline root circle RC12 to the radially outermost ends 40A of the plurality of outer spline teeth 40 . The sum of the additional radial lengths RL12 is equal to or greater than 20 mm. In this embodiment, the sum of the additional radial lengths RL12 is 31. 2mm. However, the sum of the additional radial lengths RL12 is not limited to this embodiment. At least one of the at least ten external spline teeth 40 is circumferentially symmetrical with respect to the reference line CL1. In the radial direction with respect to the rotation center axis A1 , the reference line CL1 extends from the rotation center axis A1 to the circumferential center point CP1 of the radially outermost end 40A of the at least one of the at least ten outer spline teeth 40 . However, at least one of the outer spline teeth 40 may have an asymmetric shape with respect to the reference line CL1. The at least one of the at least ten external spline teeth 40 includes an external spline drive surface 48 and an external spline non-drive surface 50 . At least one of the plurality of external splined drive surfaces 48 has a first external splined surface angle AG11. A first outer spline surface angle AG11 is defined between the outer spline drive surface 48 and the first radial line L11. The first radial line L11 extends from the rotation center axis A1 of the bicycle rear hub assembly 12 to the radially outermost edge 48A of the outer splined drive surface 48 . The first outer pitch angle PA11 or the second outer pitch angle PA12 is defined between adjacent first radial lines L11 (see, eg, FIG. 23 ). At least one of the external splined non-drive surfaces 50 has a second external splined surface angle AG12. A second external spline surface angle AG12 is defined between the external spline non-drive surface 50 and the second radial line L12. The second radial line L12 extends from the rotational central axis A1 of the bicycle rear hub assembly 12 to the radially outermost edge 50A of the outer splined non-transmission surface 50 . In this embodiment, the second external spline surface angle AG12 is equal to the first external spline surface angle AG11. However, the first external spline surface angle AG11 may be different from the second external spline surface angle AG12. The first external spline surface angle AG11 is equal to or smaller than 6 degrees. The first external spline surface angle AG11 is equal to or greater than 0 degrees. The second external spline surface angle AG12 is equal to or less than 6 degrees. The second external spline surface angle AG12 is equal to or greater than 0 degrees. In this embodiment, the first external spline surface angle AG11 is 5 degrees. The second external spline surface angle AG12 is 5 degrees. However, the first external spline surface angle AG11 and the second external spline surface angle AG12 are not limited to this embodiment and the above range. As seen in FIGS. 27 and 28 , the brake rotor support body 34 includes at least one additional external spline tooth 52 configured to engage the bicycle brake rotor 16 ( FIG. 1 ). In this embodiment, the brake rotor support body 34 includes an additional base support 54 and a plurality of additional external spline teeth 52 . The additional base support 54 has a tubular shape and extends from the hub body 36 along the rotational center axis A1. Additional external spline teeth 52 extend radially outward from an additional base support 54 . The total number of additional external spline teeth 52 is fifty-two. However, the total number of additional external spline teeth 52 is not limited to this embodiment. As seen in Figure 28, at least one additional external spline tooth 52 has an additional external spline top diameter DM14. As seen in Fig. 29, the extra external spline top diameter DM14 is larger than the external spline top diameter DM11. Additional outer spline top diameter DM14 is substantially equal to larger diameter portion 42 outer diameter DM13 . However, the additional external spline top diameter DM14 may be equal to or smaller than the external spline top diameter DM11. The additional outer spline top diameter DM14 may be different from the larger diameter portion 42 outer diameter DM13 . As seen in FIG. 29, the hub body 36 includes a first spoke mounting portion 36A and a second spoke mounting portion 36B. A plurality of first spokes SK1 are coupled to the first spoke mounting portion 36A. A plurality of second spokes SK2 are coupled to the second spoke mounting portion 36B. In this embodiment, the first spoke mounting portion 36A includes a plurality of first attachment holes 36A1. The first spoke SK1 extends through the first attachment hole 36A1. The second spoke mounting portion 36B includes a plurality of second attachment holes 36B1. The second spoke SK2 extends through the second attachment hole 36B1. As used herein, the term "spoke mounting portion" encompasses a configuration in which the spoke mounting opening has a flange-like shape such that the spoke mounting portion extends radially outward relative to the central axis of rotation of the bicycle rear hub assembly as seen in FIG. shape, and the spoke mounting portion is a configuration of an opening formed directly on the radially outer peripheral surface of the hub main body. The second spoke mounting portion 36B is spaced apart from the first spoke mounting portion 36A in the axial direction D2. The first spoke mounting portion 36A is disposed between the sprocket support body 28 and the second spoke mounting portion 36B in the axial direction D2. The second spoke mounting portion 36B is disposed between the first spoke mounting portion 36A and the brake rotor supporting body 34 in the axial direction D2. The first spoke mounting portion 36A has a first axially outermost portion 36C. The second spoke mounting portion 36B has a second axially outermost portion 36D. The first axially outermost portion 36C includes a surface facing the first frame BF1 upward in the axial direction D2 in the state where the bicycle rear hub assembly 12 is mounted to the bicycle frame BF. The second axially outermost portion 36D includes a surface facing the second frame BF2 upward in the axial direction D2 in the state where the bicycle rear hub assembly 12 is mounted to the bicycle frame BF. Hub body 36 includes a first axial length AL1. The first axial length AL1 is defined between the first axially outermost portion 36C of the first spoke mounting portion 36A and the second spoke mounting portion in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 Between the second axial portion 36B and the outermost portion 36D. The first axial length AL1 may be equal to or greater than 55 mm. The first axial length AL1 may be equal to or greater than 60 mm. The first axial length AL1 may be equal to or greater than 65 mm. In this embodiment, the first axial length AL1 may be 67 mm. However, the first axial length AL1 is not limited to this embodiment and the above range. Examples of the first axial length AL1 include 55. 7 mm, 62. 3mm and 67mm. As seen in FIG. 29 , the hub axle 30 includes a first axial frame abutment surface 30B1 and a second axial frame abutment surface 30C1 . After the bicycle rear hub assembly 12 is mounted under the bicycle frame BF, the first axial frame abutment surface 30B1 is configured to abut the bicycle frame in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 The first part of BF BF12. The second axial frame abutment surface 30C1 is configured to abut the second portion BF22 of the bicycle frame BF in the axial direction D2 in the state where the bicycle rear hub assembly 12 is mounted to the bicycle frame BF. The first axial frame abutment surface 30B1 is positioned closer to the sprocket support body 28 in the axial direction D2 than the second axial frame abutment surface 30C1 . The sprocket support body 28 is disposed between the first axial frame abutment surface 30B1 and the second axial frame abutment surface 30C1 in the axial direction D2. The hub axle 30 includes a second axial length AL2 defined in the axial direction D2 between the first axial frame abutment surface 30B1 and the second axial frame abutment surface 30C1 . The second axial length AL2 may be equal to or greater than 140 mm. Second axial length AL2 may be equal to or greater than 145 mm. Second axial length AL2 may be equal to or greater than 147 mm. Second axial length AL2 may be 148 mm. However, the second axial length AL2 is not limited to this embodiment and the above range. Examples of the second axial length AL2 include 142 mm, 148 mm, and 157 mm. The ratio of the first axial length AL1 to the second axial length AL2 may be equal to or greater than 0. 3. The ratio of the first axial length AL1 to the second axial length AL2 may be equal to or greater than 0. 4. The ratio of the first axial length AL1 to the second axial length AL2 may be equal to or greater than 0. 5. For example, the ratio of the first axial length AL1 (67 mm) to the second axial length AL2 (148 mm) is approximately 0. 45. However, the ratio of the first axial length AL1 to the second axial length AL2 is not limited to this embodiment and the above range. Examples of the ratio of the first axial length AL1 to the second axial length AL2 include approximately 0. 42 (AL1 is 62. 3 mm and AL2 is 148 mm), or including approximately 0. 39 (AL1 is 55. 7 mm and AL2 is 142 mm). As seen in FIG. 6 , the sprocket support body 28 includes a first axial end 28B, a second axial end 28C, and an axial sprocket abutment surface 28D. The second axial end 28C is opposed to the first axial end 28B in the axial direction D2. The axial center plane CPL bisects the second axial length AL2 in the axial direction D2. The axial sprocket abutment surface 28D is positioned closer to the axial center plane CPL of the bicycle rear hub assembly 12 in the axial direction D2 than the first axial end 28B. The second axial end 28C is positioned axially closer to the axial center plane CPL of the bicycle rear hub assembly 12 in the axial direction D2 than the sprocket abutment surface 28D. In this embodiment, the axial sprocket abutment surface 28D is provided on the larger diameter portion 42 , however the axial sprocket abutment surface 28D may be provided on other portions of the bicycle rear hub assembly 12 as desired. In a state where the bicycle rear sprocket assembly 14 is mounted on the sprocket support body 28 , the axial sprocket abutment surface 28D is in contact with the bicycle rear sprocket assembly 14 . The axial sprocket abutment surface 28D faces the first axial end 28B in the axial direction D2. As seen in FIG. 6 , the sprocket arrangement axial length AL3 is defined in the axial direction D2 between the first axial frame abutment surface 30B1 and the axial sprocket abutment surface 28D of the sprocket support body 28 . In this embodiment, the axial length AL3 of the sprocket arrangement ranges from 35 mm to 45 mm. For example, the sprocket configuration axial length AL3 is 39. 64mm. For example, by omitting the larger diameter portion 42, the sprocket configuration axial length AL3 can also be extended up to 44. 25mm. However, the sprocket configuration axial length AL3 is not limited to this embodiment and the above range. The larger diameter portion 42 has an axial end 42A furthest from the first axial frame abutment surface 30B1 in the axial direction D2. The additional axial length AL4 is defined in the axial direction D2 from the first axial frame abutment surface 30B1 to the axial end 42A. The additional axial length AL4 ranges from 38 mm to 47 mm. The additional axial length AL4 may range from 44 mm to 45 mm. The additional axial length AL4 may also range from 40 mm to 41 mm. In this embodiment, the additional axial length AL4 is 44. 25mm. However, the additional axial length AL4 is not limited to this embodiment and the above range. The larger diameter axial length AL5 of the larger diameter portion 42 ranges from 3 mm to 6 mm. In this embodiment, the larger diameter axial length AL5 is 4. 61mm. However, the larger diameter axial length AL5 is not limited to this embodiment and the above range. The ratio of the first axial length AL1 to the sprocket configuration axial length AL3 ranges from 1. 2 to 1. 7. For example, if the first axial length AL1 is 55. 7 mm and the sprocket configuration axial length AL3 is 39. 64 mm, the ratio of the first axial length AL1 to the sprocket configuration axial length AL3 is 1. 4. However, the ratio of the first axial length AL1 to the sprocket configuration axial length AL3 is not limited to this embodiment and the above scope. For example, if the first axial length AL1 is 62. 3 mm and the sprocket configuration axial length AL3 is 39. 64 mm, the ratio of the first axial length AL1 to the sprocket configuration axial length AL3 can be 1. 57, or if the first axial length AL1 is 67 mm and the sprocket configuration axial length AL3 is 39. 64 mm, the ratio of the first axial length AL1 to the sprocket configuration axial length AL3 can be 1. 69. As seen in FIG. 30 , the sprocket support member 37 includes a hub engaging portion 60 and a plurality of support arms 62 . A plurality of support arms 62 extend radially outward from the hub engaging portion 60 . The support arm 62 includes a first attachment portion 62A to an eighth attachment portion 62H. The plurality of spacers 38 includes a plurality of first spacers 38A, a plurality of second spacers 38B, a plurality of third spacers 38C, a plurality of fourth spacers 38D, a plurality of fifth spacers 38E, and a plurality of sixth spacers. The spacer 38F and a plurality of seventh spacers 38G. As seen in FIG. 6 , the first spacer 38A is disposed between the additional sprockets SP5 and SP6 . The second spacer 38B is disposed between the additional sprockets SP6 and SP7. The third spacer 38C is disposed between the additional sprockets SP7 and SP8. The fourth spacer 38D is disposed between the additional sprockets SP8 and SP9. The fifth spacer 38E is disposed between the additional sprockets SP9 and SP10. The sixth spacer 38F is disposed between the additional sprockets SP10 and SP11. The seventh spacer 38G is disposed between the additional sprockets SP11 and SP12. The additional sprocket SP6 and the first spacer 38A are attached to the first attachment portion 62A by the adhesive 37A. The additional sprocket SP7 and the second spacer 38B are attached to the second attachment portion 62B by the adhesive 37A. The additional sprocket SP8 and the third spacer 38C are attached to the third attachment portion 62C by the adhesive 37A. The additional sprocket SP9 and the fourth spacer 38D are attached to the fourth attachment portion 62D by the adhesive 37A. The additional sprocket SP10 and the fifth spacer 38E are attached to the fifth attachment portion 62E by the adhesive 37A. The additional sprocket SP11 and the sixth spacer 38F are attached to the sixth attachment portion 62F by the adhesive 37A. The additional sprocket SP12 and the seventh spacer 38G are attached to the seventh attaching portion 62G by the adhesive 37A. The additional sprockets SP5 and 39B are attached to the eighth attachment portion 62H by the adhesive 37A. The hub engaging portion 60 , the sprockets SP1 to SP4 , the first ring 39A and the second ring 39B are held between the larger diameter portion 42 and the radial protrusion 32C of the locking member 32 in the axial direction D2 . In this embodiment, each of the sprockets SP1 to SP12 is made of a metal material such as aluminum, iron, or titanium. The sprocket supporting member 37 is made of non-metallic material including resin material. Each of the first spacer 38A to seventh spacer 38G, the first ring 39A, and the second ring 39B is made of a non-metallic material such as a resin material. However, at least one of the sprockets SP1 to SP12 may be at least partially made of a non-metallic material. Each of the sprocket support member 37 , the first spacer 38A to the seventh spacer 38G, the first ring 39A and the second ring 39B is at least partially made of a metal material such as aluminum, iron, or titanium. As seen in FIG. 7 , the first sprocket SP1 includes a first opening SP1K. The first opening SP1K has a first minimum diameter MD1. As seen in FIG. 31 , in a state where the bicycle rear sprocket assembly 14 is mounted to the sprocket support body 28 , the tubular body 32A of the locking member 32 extends through the first opening SP1K of the first sprocket SP1 . In the state where the bicycle rear sprocket assembly 14 is mounted to the sprocket support body 28, the first opening SP1K of the first sprocket SP1 is configured such that the first axial end 32D of the tubular body 32A of the locking member 32 passes through the second opening SP1K. A first opening SP1K of the sprocket SP1. The first axial end 28B of the sprocket support body 28 is spaced from the first opening SP1K of the first sprocket SP1 without extending through the first opening SP1K. The first minimum diameter MD1 is smaller than the minimum outer diameter MD28 of the sprocket support body 28 of the bicycle rear hub assembly 12 . In this embodiment, the minimum outer diameter MD28 is equal to the outer spline base diameter DM12 ( FIG. 26 ) of the plurality of outer spline teeth 40 of the sprocket support body 28 . As seen in FIG. 31 , the tubular body 32A has a first outer diameter ED1 equal to or less than 27 mm. The first outer diameter ED1 is equal to or greater than 26 mm. The radial protrusion 32C has a second outer diameter ED2 equal to or smaller than 32 mm. The second outer diameter ED2 is equal to or greater than 30 mm. In this embodiment, the first outer diameter ED1 is 26. 2 mm. The second outer diameter ED2 is 30. 8 mm. However, at least one of the first outer diameter ED1 and the second outer diameter ED2 is not limited to this embodiment and the above range. The radial protrusion 32C has an axial width ED3 defined in the axial direction D2. For example, the axial width ED3 of the radial protrusion 32C is 2 mm. However, the axial width ED3 is not limited to this embodiment. The locking member 32 has an axial length ED4 defined in the axial direction D2 from the radial protrusion 32C to the first axial end 32D. The axial length ED4 of the locking member 32 is 10 mm. However, the axial length ED4 is not limited to this embodiment. As seen in FIG. 8, the first sprocket SP2 includes a first opening SP2K. That is, each of the plurality of first sprockets SP1 and SP2 includes a first opening. The first opening SP2K has a first minimum diameter MD2. As seen in FIG. 31 , in a state where the bicycle rear sprocket assembly 14 is mounted to the sprocket support body 28 , the tubular body 32A of the locking member 32 extends through the first opening SP2K of the first sprocket SP2 . The first axial end 28B of the sprocket support body 28 is spaced from the first opening SP2K of the first sprocket SP2 without extending through the first opening SP2K. The first minimum diameter MD2 is smaller than the minimum outer diameter MD28 of the sprocket support body 28 of the bicycle rear hub assembly 12 . As seen in FIG. 9 , the second sprocket SP3 includes a second opening SP3K. The second opening SP3K has a second minimum diameter MD3. As seen in FIG. 31 , in a state where the bicycle rear sprocket assembly 14 is mounted to the sprocket support body 28, the tubular body 32A of the locking member 32 and the sprocket support body 28 extend through the second opening of the second sprocket SP3. SP3K. The first axial end 28B of the sprocket supporting body 28 is disposed between the second opening SP3K and the first opening SP1K in the axial direction D2. The first axial end 28B of the sprocket supporting body 28 is disposed between the second opening SP3K and the first opening SP2K in the axial direction D2. The second minimum diameter MD3 is equal to or greater than the minimum outer diameter MD28 of the sprocket support body 28 of the bicycle rear hub assembly 12 . As seen in FIG. 10, the second sprocket SP4 includes a second opening SP4K. That is, each of the plurality of second sprockets SP3 and SP4 includes a second opening. The second opening SP4K has a second minimum diameter MD4. As seen in FIG. 31 , in a state where the bicycle rear sprocket assembly 14 is mounted to the sprocket support body 28 , the sprocket support body 28 extends through the second opening SP4K of the second sprocket SP4 . The first axial end 28B of the sprocket supporting body 28 is disposed between the second opening SP4K and the first opening SP1K in the axial direction D2. The second minimum diameter MD4 is equal to or greater than the minimum outer diameter MD28 of the sprocket support body 28 of the bicycle rear hub assembly 12 . As seen in FIG. 32 , the first sprocket SP2 includes at least ten inner spline teeth 63 configured to engage the sprocket support body 28 of the bicycle rear hub assembly 12 . At least ten internal spline teeth 63 are provided to the first opening SP2K. At least ten internal spline teeth 63 provide a first torque transmitting structure of the first sprocket SP2, as described later. The total number of at least ten inner spline teeth 63 of the first sprocket SP2 is equal to or greater than twenty. The total number of at least ten internal spline teeth 63 of the first sprocket SP2 is equal to or greater than 28. The total number of internal spline teeth 63 is equal to or less than 72. In this embodiment, the total number of internal spline teeth 63 is twenty-nine. However, the total number of internal spline teeth 63 is not limited to this embodiment and the above range. As seen in FIG. 9 , the second sprocket SP3 includes at least ten inner spline teeth 64 configured to engage the sprocket support body 28 of the bicycle rear hub assembly 12 . In this embodiment, the at least ten inner spline teeth 64 of the second sprocket SP3 define the second minimum diameter MD3 as the inner spline base diameter of the at least ten inner spline teeth 64 . The total number of the at least ten internal spline teeth 64 of the second sprocket SP3 is equal to or greater than twenty. The total number of at least ten inner spline teeth 64 of the second sprocket SP3 is equal to or greater than twenty-eight. The total number of internal spline teeth 64 is 72 or less. In this embodiment, the total number of internal spline teeth 64 is twenty-nine. However, the total number of internal spline teeth 64 is not limited to this embodiment and above. As seen in FIG. 10 , the second sprocket SP4 includes at least ten inner spline teeth 65 configured to engage the sprocket support body 28 of the bicycle rear hub assembly 12 . That is, the plurality of second sprockets SP3 and SP4 each include at least ten internal spline teeth configured to engage with the sprocket support body 28 of the bicycle rear hub assembly 12 . In this embodiment, the at least ten inner spline teeth 65 of the second sprocket SP4 define the second minimum diameter MD4 as the inner spline base diameter of the at least ten inner spline teeth 65 . The total number of at least ten internal spline teeth 65 of the second sprocket SP4 is equal to or greater than twenty. The total number of at least ten internal spline teeth 65 of the second sprocket SP4 is equal to or greater than twenty-eight. The total number of internal spline teeth 65 is equal to or less than 72. In this embodiment, the total number of internal spline teeth 65 is twenty-nine. However, the total number of internal spline teeth 65 is not limited to this embodiment and the above range. As seen in FIG. 33 , the at least ten inner spline teeth 64 of the second sprocket SP3 have a first inner circumferential pitch angle PA21 and a second inner circumferential pitch angle PA22 . At least two of the at least ten internal spline teeth 64 of the second sprocket SP3 are arranged along the circumference at a first internal circumferential pitch angle PA21 relative to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . At least two of the at least ten internal spline teeth 64 adjoin each other in the circumferential direction D1 without another spline tooth in between. In other words, at least two of the plurality of internal spline teeth 64 are arranged along the circumference at the first internal circumferential pitch angle PA21 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 . Among the at least ten internal spline teeth 64 of the second sprocket SP3 , at least two other internal spline teeth are arranged along the circumference at a second internal circumferential pitch angle PA22 relative to the rotation central axis A1 . At least two other inner spline teeth of the at least ten inner spline teeth 64 of the second sprocket SP3 adjoin each other in the circumferential direction D1 without another spline tooth in between. In other words, at least two of the plurality of internal spline teeth 64 of the second sprocket SP3 are arranged along the circumference at the second internal circumferential pitch angle PA22 with respect to the rotation central axis A1 . In this embodiment, the second inner circumferential pitch angle PA22 is different from the first inner circumferential pitch angle PA21. However, the second inner circumferential pitch angle PA22 may be substantially equal to the first inner circumferential pitch angle PA21. In this embodiment, the inner spline teeth 64 are circumferentially arranged at the first inner circumferential pitch angle PA21 in the circumferential direction D1. Two of the inner spline teeth 64 are arranged at the second inner circumferential pitch angle PA22 in the circumferential direction D1. However, at least two of the inner spline teeth 64 may be arranged at another inner circumferential pitch angle in the circumferential direction D1. The first internal pitch angle PA21 ranges from 5 degrees to 36 degrees. The first internal pitch angle PA21 ranges from 10 degrees to 20 degrees. The first inner circumferential pitch angle PA21 is equal to or smaller than 15 degrees. In this embodiment, for example, the first inner circumferential pitch angle PA21 is 12 degrees. However, the first internal pitch angle PA21 is not limited to this embodiment and the above range. The second inner circumferential pitch angle PA22 ranges from 5 degrees to 36 degrees. In this embodiment, the second inner circumferential pitch angle PA22 is 24 degrees. However, the second inner circumferential pitch angle PA22 is not limited to this embodiment and the above range. At least one of the at least ten inner spline teeth 64 of the second sprocket SP3 has a first spline shape different from the second spline shape of another one of the at least ten inner spline teeth 64 . At least one of the at least ten internal spline teeth 64 of the second sprocket SP3 has a first spline size that is different from the second spline size of another of the at least ten internal spline teeth 64 . At least one of the at least ten internal spline teeth 64 has a cross-sectional shape that is different from the cross-sectional shape of another of the at least ten internal spline teeth 64 . However, as seen in Fig. 34, the inner spline teeth 64 may have the same shape as each other. At least ten internal spline teeth 64 may be the same size as one another. At least ten internal spline teeth 64 may have the same cross-sectional shape as one another. As seen in FIG. 35 , at least one of the at least ten internal spline teeth 64 includes an internal spline drive surface 66 . At least one of the at least ten internal spline teeth 64 includes an internal spline non-drive surface 68 . The at least ten internal spline teeth 64 include a plurality of internal spline drive surfaces 66 to receive drive rotational force F1 from the bicycle rear hub assembly 12 ( FIG. 6 ) during pedaling. The at least ten internal spline teeth 64 include a plurality of internal spline non-drive surfaces 68 . The inner splined drive surface 66 may contact the sprocket support body 28 to transfer the drive rotational force F1 from the sprocket SP1 to the sprocket support body 28 during pedaling. The inner splined drive surface 66 faces the drive rotational direction D11. The inner splined drive surface 66 faces the inner splined drive surface 48 of the bicycle rear hub assembly 12 when the bicycle rear sprocket assembly 14 is mounted to the bicycle rear hub assembly 12 . The internal spline non-transmission surface 68 is disposed on the opposite side of the internal spline transmission surface 66 in the circumferential direction D1. The inner splined non-drive surface 68 faces the counter-rotational direction D12 so that the drive rotational force F1 is not transmitted from the sprocket SP1 to the sprocket support body 28 during pedaling. The outer splined non-drive surface 68 faces the inner splined non-drive surface 50 of the bicycle rear hub assembly 12 in a state where the bicycle rear sprocket assembly 14 is mounted to the bicycle rear hub assembly 12 . At least ten inner spline teeth 64 each have a circumferential maximum width MW2. The inner spline teeth 64 each have a maximum circumferential width MW2. The circumferential maximum width MW2 is defined as the maximum width receiving the thrust force F3 applied to the inner spline teeth 64 . The circumferential maximum width MW2 is defined as the linear distance based on the internal spline drive surface 66 . The plurality of inner splined drive surfaces 66 each include a radially outermost edge 66A and a radially innermost edge 66B. The second reference circle RC21 is defined on the radially outermost edge 66A and centered on the rotation central axis A1. The second reference circle RC21 intersects the inner splined non-drive surface 68 at a reference point 68R. The circumferential maximum width MW2 extends linearly in the circumferential direction D1 from the radially innermost edge 66B to the reference point 68R. The inner splined non-drive surface 68 includes a radially outermost edge 68A and a radially innermost edge 68B. The inner splined non-drive surface 68 extends from a radially outermost edge 68A to a radially innermost edge 68B. Reference point 68R is disposed between radially outermost edge 68A and radially innermost edge 68B. The sum of the maximum circumferential widths MW2 is equal to or greater than 40 mm. The sum of the maximum circumferential widths MW2 may be equal to or greater than 45 mm. The sum of the maximum circumferential widths MW2 may be equal to or greater than 50 mm. In this embodiment, the sum of the maximum circumference width MW2 is 50. 8 mm. However, the sum of the circumferential maximum widths MW2 is not limited to this embodiment. As seen in FIG. 36, at least ten inner spline teeth 64 of the second sprocket SP3 have an inner spline top diameter DM21. At least one inner spline tooth 64 of the second sprocket SP3 has an inner spline root circle RC22 with an inner spline crest diameter DM21 . Internal spline top diameter DM21 is equal to or less than 34 mm. The inner spline top diameter DM21 of the second sprocket SP3 is equal to or smaller than 33 mm. The inner spline top diameter DM21 of the second sprocket SP3 is equal to or greater than 29 mm. In this embodiment, the inner spline top diameter DM21 of the second sprocket SP3 is 32. 8mm. However, the inner spline top diameter DM21 of the second sprocket SP3 is not limited to this embodiment and the above range. At least ten internal spline teeth 64 of the second sprocket SP3 have an internal spline base diameter DM22 equal to or smaller than 32 mm. Internal spline bottom diameter DM22 is equal to or less than 31 mm. Internal spline bottom diameter DM22 is equal to or greater than 28 mm. In this embodiment, the internal spline bottom diameter DM22 is 30. 4 mm. However, the internal spline bottom diameter DM22 is not limited to this embodiment and the above range. As seen in FIG. 18, the extra sprocket SP12 has the largest tooth tip diameter TD12. The maximum tooth tip diameter TD12 is the maximum outer diameter defined by the plurality of sprocket teeth SP12B. The ratio of the internal spline top diameter DM21 (Fig. 36) to the maximum tooth tip diameter TD12 ranges from 0. 15 to 0. 18. In this embodiment, the ratio of the inner spline top diameter DM21 to the maximum tooth tip diameter TD12 is 0. 15. However, the ratio of the inner spline top diameter DM21 to the maximum tooth tip diameter TD12 is not limited to this embodiment and the above range. As seen in FIG. 35, the plurality of inner splined drive surfaces 66 includes a radially outermost edge 66A and a radially innermost edge 66B. The plurality of inner splined drive surfaces 66 each include a radial length RL21 defined from a radially outermost edge 66A to a radially innermost edge 66B. The sum of the radial lengths RL21 of the plurality of internal spline transmission surfaces 66 is equal to or greater than 7 mm. The sum of the radial lengths RL21 is equal to or greater than 10 mm. The sum of the radial lengths RL21 is equal to or greater than 15 mm. In this embodiment, the sum of the radial lengths RL21 is equal to or less than 36 mm. In this embodiment, the sum of the radial lengths RL21 is 16. 6 mm However, the sum of the radial lengths RL21 is not limited to this embodiment and the above range. The plurality of internal spline teeth 64 has an additional radial length RL22. The additional radial length RL22 is defined from the inner spline root circle RC22 to the radially innermost end 64A of the plurality of inner spline teeth 64 , respectively. The sum of the additional radial lengths RL22 is equal to or greater than 12 mm. In this embodiment, the sum of the additional radial lengths RL22 is 34. 8mm. However, the sum of the additional radial lengths RL22 is not limited to this embodiment and the above range. At least one of the at least ten inner spline teeth 64 of the second sprocket SP3 is circumferentially symmetrical with respect to the reference line CL2. In a radial direction with respect to the central axis of rotation A1 , the reference line CL2 extends from the central axis of rotation A1 to a circumferential center point CP2 of the radially outermost end 64A of at least one of the at least ten internal spline teeth 64 . However, at least one of the internal spline teeth 64 may have an asymmetric shape with respect to the reference line CL2. At least one of the internal spline teeth 64 includes an internal spline drive surface 66 and an internal spline non-drive surface 68 . The inner splined drive surface 66 has a first inner splined surface angle AG21. A first internal spline surface angle AG21 is defined between the internal spline drive surface 66 and the first radial line L21. The first radial line L21 extends from the central axis of rotation A1 of the bicycle rear sprocket assembly 14 to the radially outermost edge 66A of the inner splined drive surface 66 . The first inner circumferential pitch angle PA21 or the second inner circumferential pitch angle PA22 is defined between adjacent first radial lines L21 (see, eg, FIG. 33 ). The internal splined non-drive surface 68 has a second internal splined surface angle AG22. A second internal spline surface angle AG22 is defined between the internal spline non-drive surface 68 and the second radial line L22. The second radial line L22 extends from the central axis of rotation A1 of the bicycle rear sprocket assembly 14 to the radially outermost edge 68A of the inner splined non-drive surface 68 . In this embodiment, the second internal spline surface angle AG22 is equal to the first internal spline surface angle AG21. However, the first internal spline surface angle AG21 may be different from the second internal spline surface angle AG22. The first internal spline surface angle AG21 is between 0° and 6°. The second internal spline surface angle AG22 ranges from 0° to 6°. In this embodiment, the first internal spline surface angle AG21 is 5 degrees. The second internal spline surface angle AG22 is 5 degrees. However, the first internal spline surface angle AG21 and the second internal spline surface angle AG22 are not limited to this embodiment and the above range. As seen in FIG. 37 , the inner spline teeth 64 mesh with the outer spline teeth 40 to transmit the transmission rotational force F1 from the second sprocket SP3 to the sprocket support body 28 . The inner splined drive surface 66 may contact the outer splined drive surface 48 to transmit the drive rotational force F1 from the second sprocket SP3 to the sprocket support body 28 . In the state where the inner splined drive surface 66 is in contact with the outer splined drive surface 48 , the inner splined non-drive surface 68 is spaced apart from the outer splined non-drive surface 50 . The internal spline teeth 63 of the first sprocket SP2 and the internal spline teeth 65 of the second sprocket SP4 have substantially the same structure as the internal spline teeth 64 of the second sprocket SP3. Therefore, for the sake of brevity, no detailed description will be given here. As seen in FIG. 2 , the sprocket support member 37 includes at least ten internal spline teeth 76 configured to engage the sprocket support body 28 of the bicycle rear hub assembly 12 . The plurality of internal spline teeth 76 has substantially the same structure as the plurality of internal spline teeth 64 . Therefore, for the sake of brevity, no detailed description will be given here. As seen in FIG. 38 , the first sprocket SP1 includes a first torque transmitting structure SP1T provided to the first inner side SP1H to directly or indirectly transmit pedaling torque to the sprocket support body 28 . In this embodiment, the first torque transmission structure SP1T includes a plurality of first torque transmission teeth SP1T1 to indirectly transmit the pedaling torque to the sprocket supporting body 28 . The first torque transmitting structure SP1T includes at least ten first torque transmitting teeth SP1T1. Preferably, the total number of at least ten first torque transmission teeth SP1T1 is equal to or greater than twenty. More preferably, the total number of at least ten first torque transmitting teeth SP1T1 is equal to or greater than 28. In this embodiment, the total number of at least ten first torque transmitting teeth SP1T1 is twenty-nine. However, the total number of at least ten first torque transmission teeth SP1T1 is not limited to this embodiment and the above range. As seen in FIGS. 38 and 39 , the first sprocket SP2 includes a first inner SP2H and a first outer SP2G. With respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14 , the first outward SP2G is opposed to the first inner SP2H in the axial direction D2 . The first sprocket SP2 includes a first torque transmitting structure SP2M provided to the first inward side SP2H to directly or indirectly transmit pedaling torque to the sprocket supporting body 28 . In this embodiment, the inner spline teeth 63 of the first sprocket SP2 may also be referred to as first torque transmission teeth 63 . The first torque transmission structure SP2M includes a plurality of first torque transmission teeth 63 to directly transmit the pedaling torque to the sprocket supporting body 28 . The first torque transmitting structure SP2M includes at least ten first torque transmitting teeth 63 . Preferably, the total number of at least ten first torque transmitting teeth 63 is equal to or greater than twenty. More preferably, the total number of at least ten first torque transmitting teeth 63 is equal to or greater than twenty-eight. In this embodiment, the total number of at least ten first torque transmitting teeth 63 is twenty-nine. However, the total number of at least ten first torque transmission teeth 63 is not limited to this embodiment and the above range. The first torque transmitting teeth 63 may also be referred to as inner spline teeth 63 . As seen in FIG. 39, the first sprocket SP2 includes a second torque transmitting structure SP2T for receiving the pedaling torque from the first sprocket SP1. The second torque transmitting structure SP2T is disposed on the first outwardly facing SP2G. In this embodiment, the second torque transfer structure SP2T includes a plurality of second torque transfer teeth SP2T1. Preferably, the total number of second torque transmission teeth SP2T1 is equal to or greater than twenty. More preferably, the total number of second torque transmission teeth SP2T1 is equal to or greater than 28. In this embodiment, the total number of second torque transmitting teeth SP2T1 is twenty-nine. However, the total number of second torque transmission teeth SP2T1 is not limited to this embodiment and the above range. The first torque transmitting structure SP1T is engaged with the second torque transmitting structure SP2T. The plurality of first torque transmission teeth SP1T1 meshes with the plurality of second torque transmission teeth SP2T1 to transmit the transmission rotational force F1. As seen in FIGS. 23 and 24 , the sprocket support body 28 includes a hub indicator 28I disposed at an axial end of the base support 41 . The hub indicator 28I is disposed in the region of the second outer peripheral pitch angle PA12 when viewed along the rotational center axis A1. In this embodiment, hub indicator 281 includes dots. However, hub indicator 281 may include other shapes, such as triangles and lines. Additionally, the hub indicator 281 may be a separate component attached to the sprocket support body 28 by an engaging structure such as an adhesive. The position of the hub indicator 28I is not limited to this embodiment. As seen in FIG. 7 , the first sprocket SP1 includes a sprocket indicator SP1I provided at an axial end of the sprocket main body SP1A. In this embodiment, the sprocket indicator SP1I includes dots. However, the sprocket indicator SP1I may include other shapes, such as triangles and lines. Additionally, the sprocket indicator SP1I may be a separate member attached to the sprocket SP1 by an engaging structure such as an adhesive. The position of the sprocket indicator SP1I is not limited to this embodiment. Sprocket indicator SP1I may be provided to any of the other sprockets SP2-SP12. A sprocket indicator SP1I may also be provided to the sprocket support member 37 . As seen in FIG. 6 , the bicycle rear hub assembly 12 further includes a freewheel structure 78 . The sprocket support body 28 is operatively coupled to the hub body 36 by a freewheel structure 78 . The freewheel structure 78 is configured to couple the sprocket support body 28 to the hub body 36 to rotate the sprocket support body 28 along with the hub body 36 in the drive rotation direction D11 ( FIG. 5 ) during pedaling. The freewheel structure 78 is configured to allow the sprocket support body 28 to rotate relative to the hub body 36 in a counter-rotational direction D12 ( FIG. 5 ) during idling. Therefore, the freewheel structure 78 can be interpreted as a one-way clutch structure 78 . The freewheel structure 78 will be described in detail later. The bicycle rear hub assembly 12 includes a first bearing 79A and a second bearing 79B. The first bearing 79A and the second bearing 79B are provided between the sprocket supporting body 28 and the hub axle 30 to rotatably support the sprocket supporting body 28 with respect to the hub axle 30 about the rotation center axis A1. In this embodiment, each of the sprocket support body 28, the brake rotor support body 34 and the hub body 36 is made of a metal material such as aluminum, iron or titanium. However, at least one of the sprocket support body 28, the brake rotor support body 34, and the hub body 36 may be made of a non-metallic material. As seen in FIG. 40 , the freewheel structure 78 includes a first ratchet member 80 and a second ratchet member 82 . The first ratchet member 80 is configured to torque-transmittingly engage one of the hub body 36 and the sprocket support body 28 . The second ratchet member 82 is configured to torque-transmittingly engage the other of the hub body 36 and the sprocket support body 28 . In this embodiment, the first ratchet member 80 is torque-transmittingly engaged with the sprocket support body 28 . The second ratchet member 82 is torque-transmittingly engaged with the hub body 36 . However, the first ratchet member 80 may be configured to torque-transmittingly engage the hub body 36 . The second ratchet member 82 may be configured to torque-transmittingly engage the sprocket support body 28 . The first ratchet member 80 is mounted to the sprocket support body 28 to rotate with the sprocket support body 28 relative to the hub body 36 about the rotation center axis A1. The second ratchet member 82 is mounted to the hub body 36 to rotate with the hub body 36 about the rotation center axis A1 relative to the sprocket support body 28 . Each of the first ratchet member 80 and the second ratchet member 82 has a ring shape. At least one of the first ratchet member 80 and the second ratchet member 82 is movable relative to the hub axle 30 in the axial direction D2 relative to the rotation center axis A1 . In this embodiment, each of the first ratchet member 80 and the second ratchet member 82 is movable relative to the hub axle 30 in the axial direction D2. The second ratchet member 82 is movable relative to the hub body 36 in the axial direction D2. The first ratchet member 80 is movable relative to the sprocket support body 28 in the axial direction D2. The hub body 36 includes a freewheel housing 36H having an annular shape. The freewheel housing 36H extends in the axial direction D2. The first ratchet member 80 and the second ratchet member 82 are disposed in the freewheel housing 36H in an assembled state. As seen in FIG. 41 , the first ratchet member 80 includes at least one first ratchet tooth 80A. In this embodiment, at least one first ratchet tooth 80A includes a plurality of first ratchet teeth 80A. A plurality of first ratchet teeth 80A are arranged in the circumferential direction D1 to provide saw teeth. As seen in FIG. 42 , the second ratchet member 82 includes at least one second ratchet tooth 82A configured to torque-transmittingly engage the at least one first ratchet tooth 80A. The at least one second ratchet tooth 82A meshes with the at least one first ratchet tooth 80A to transmit the rotational force F1 from the sprocket support body 28 to the hub body 36 ( FIG. 40 ). In this embodiment, the at least one second ratchet tooth 82A includes a plurality of second ratchet teeth 82A configured to torque-transmittingly mesh with the plurality of first ratchet teeth 80A. The plurality of second ratchet teeth 82A are arranged in the circumferential direction D1 to provide saw teeth. The plurality of second ratchet teeth 82A can mesh with the plurality of first ratchet teeth 80A. In a state where the second ratchet teeth 82A are engaged with the first ratchet teeth 80A, the first ratchet member 80 rotates together with the second ratchet member 82 . As seen in FIGS. 41 and 42 , the sprocket support body 28 has an outer peripheral surface 28P having a first helical spline 28H. The first ratchet member 80 is configured for torque-transmitting engagement with the sprocket support body 28 and includes a second helical spline 80H cooperating with the first helical spline 28H. The first ratchet member 80 moves in the axial direction D2 relative to the sprocket support body 28 through the second helical spline 80H cooperating with the first helical spline 28H during transmission by the first thrust force applied from the sprocket support body 28 Mounted removably. In this embodiment, the first helical spline 28H includes a plurality of helical outer spline teeth 46 . The second helical spline 80H includes a plurality of helical inner spline teeth 80H1 cooperating with the plurality of helical outer spline teeth 46 . As seen in FIG. 43 , the hub body 36 includes an inner peripheral surface 36S and at least one first tooth 36T. At least one first tooth 36T is provided on the inner peripheral surface 36S. In this embodiment, the freewheel housing 36H includes an inner peripheral surface 36S. The hub body 36 includes a plurality of first teeth 36T. The plurality of first teeth 36T are disposed on the inner peripheral surface 36S, and extend radially inward from the inner peripheral surface 36S relative to the rotation center axis A1. The first teeth 36T are arranged in the circumferential direction D1 to define a plurality of grooves 36R between adjacent two teeth of the first teeth 36T. The second ratchet member 82 includes a hub body engaging portion 82E torque-transmittingly engaged with the hub body 36 via the hub body engaging portion 82E to transmit the rotational force F1 from the first ratchet member 80 to the hub body 36 . One of the hub body engaging portion 82E and the hub body 36 includes at least one radially extending protrusion. The other of hub body engaging portion 82E and hub body 36 includes at least one groove that engages the at least one protrusion. In this embodiment, the hub body engaging portion 82E includes at least one protrusion 82T extending radially as at least one protrusion. Hub body 36 includes at least one groove 36R that engages at least one protrusion 82T. In this embodiment, the hub body engaging portion 82E includes a plurality of protrusions 82T. The plurality of protrusions 82T engage with the plurality of grooves 36R. As seen in FIG. 42 , the outer peripheral surface 28P of the sprocket support body 28 has a guide portion 28G configured to guide the first ratchet member 80 toward the hub body 36 during idling. The pilot portion 28G is configured to define an obtuse angle AG28 ( FIG. 48 ) with the first helical spline 28H. The sprocket supporting body 28 includes a plurality of guide portions 28G. The guide portion 28G is configured to guide the first ratchet member 80 toward the hub body 36 during idle or lost motion. The guide portion 28G guides the first ratchet member 80 toward the hub body 36 during idling to release mating engagement between at least one first ratchet tooth 80A ( FIG. 41 ) and at least one second ratchet tooth 82A. The guide portion 28G is configured to move the first ratchet member 80 away from the second ratchet member 82 in the axial direction D2. The guide portion 28G extends at least in the circumferential direction D1 with respect to the sprocket support body 28 . The guide portion 28G extends from one of the plurality of helical outer spline teeth 46 at least in the circumferential direction D1. Although in this embodiment the guide portion 28G is provided integrally with the helical outer spline teeth 46 as a one-piece unitary member, the guide portion 28G may be a separate member from the plurality of helical outer spline teeth 46 . Due to the guide portion 28G, the first ratchet member 80 and the second ratchet member 82 disengage smoothly from each other during idling, especially if the guide portion 28G is configured to define an obtuse angle AG28 with respect to the first helical spline 28H . This also results in reduced noise during idling because the at least one first ratchet tooth 80A and the at least one second ratchet tooth 82A are smoothly separated from each other during idling. As seen in FIG. 40 , the bicycle rear hub assembly 12 further includes a biasing member 84 . A biasing member 84 is disposed between the hub body 36 and the first ratchet member 80 to bias the first ratchet member 80 toward the second ratchet member 82 in the axial direction D2. For example, in this embodiment, the biasing member 84 is a compression spring. As seen in FIG. 44 , the biasing member 84 is compressed in the axial direction D2 between the hub body 36 and the first ratchet member 80 . The biasing member 84 biases the first ratchet member 80 toward the second ratchet member 82 to maintain a meshed state in which the first ratchet member 80 and the second ratchet member 82 mesh with each other via the first ratchet teeth 80A and the second ratchet teeth 82A. Preferably, the biasing member 84 is engaged with the hub body 36 for rotation therewith. The biasing member 84 is mounted to the hub body 36 to rotate with the hub body 36 about the rotational center axis A1 ( FIG. 40 ). The biasing member 84 includes a crimped body 84A and a connecting end 84B. The hub main body 36 includes a connection hole 36F. The connection end 84B is disposed in the connection hole 36F so that the biasing member 84 rotates together with the hub main body 36 about the rotation center axis A1 ( FIG. 40 ). As seen in FIG. 44 , the outer peripheral surface 28P of the sprocket support body 28 supports the first ratchet member 80 and the second ratchet member 82 . The first ratchet member 80 includes an axial surface 80S facing the axial direction D2. At least one first ratchet tooth 80A is disposed on the axial surface 80S of the first ratchet member 80 . In this embodiment, a plurality of first ratchet teeth 80A are disposed on the axial surface 80S of the first ratchet member 80 . Axial surface 80S is generally perpendicular to axial direction D2. However, the axial surface 80S may not be perpendicular to the axial direction D2. The second ratchet member 82 includes an axial surface 82S facing the axial direction D2. At least one second ratchet tooth 82A is disposed on the axial surface 82S of the second ratchet member 82 . The axial surface 82S of the second ratchet member 82 faces the axial surface 80S of the first ratchet member 80 . In this embodiment, a plurality of second ratchet teeth 82A are disposed on the axial surface 82S of the second ratchet member 82 . Axial surface 82S is generally perpendicular to axial direction D2. However, the axial surface 82S may not be perpendicular to the axial direction D2. As seen in FIG. 40 , bicycle rear hub assembly 12 includes spacer 86 , support member 88 , slide member 90 , additional biasing member 92 and receiving member 94 . However, it is possible to omit at least one of the spacer 86 , support member 88 , slide member 90 , additional biasing member 92 , and receiving member 94 from the bicycle rear hub assembly 12 . As seen in FIGS. 44 and 45 , the spacer 86 is at least partially disposed between the at least one first tooth 36T and the at least one protrusion 82T in a circumferential direction D1 defined around the rotational center axis A1 . In this embodiment, the spacer 86 is partially disposed between the first tooth 36T and the protrusion 82T in the circumferential direction D1. However, the spacer 86 may be completely disposed between the first tooth 36T and the protrusion 82T in the circumferential direction D1. As seen in FIGS. 45-47 , spacer 86 includes at least one intermediate portion 86A disposed between at least one first tooth 36T and at least one protrusion 82T. At least one intermediate portion 86A is disposed between the at least one first tooth 36T and the at least one protrusion 82T in the circumferential direction D1. In this embodiment, the spacer 86 includes a plurality of intermediate portions 86A disposed between the first tooth 36T and the protrusion 82T in the circumferential direction D1, respectively. Although the spacer 86 includes the intermediate portions 86A in this embodiment, the spacer 86 may include one intermediate portion 86A. As seen in FIGS. 46 and 47 , the spacer 86 includes a connection portion 86B. The plurality of intermediate portions 86A extend from the connection portion 86B in an axial direction D2 parallel to the rotation center axis A1. Although the spacer 86 includes the connection portion 86B in this embodiment, the connection portion 86B may be omitted from the spacer 86 . Spacer 86 includes a non-metallic material. In this embodiment, the non-metallic material includes a resin material. Examples of resin materials include synthetic resins. Instead of or in addition to the resin material, the non-metallic material may include materials other than the resin material. Although the intermediate portion 86A and the connecting portion 86B are integrally provided with each other as a one-piece unitary member in this embodiment, at least one of the intermediate portions 86A may be a separate portion from the connecting portion 86B. As seen in FIGS. 44 and 45 , a plurality of intermediate portions 86A are disposed between the inner peripheral surface 36S of the hub body 36 and the outer peripheral surface 82P of the second ratchet member 82 in the radial direction. As seen in FIG. 44 , the support member 88 is disposed between the hub body 36 and the second ratchet member 82 in the axial direction D2. A support member 88 is attached to the second ratchet member 82 . The support member 88 is disposed radially outward from the first ratchet member 80 . The support member 88 can be in contact with the first ratchet member 80 . Support member 88 preferably comprises a non-metallic material. The support member 88 made of a non-metallic material reduces noise during operation of the bicycle rear hub assembly 12 . In this embodiment, the non-metallic material includes a resin material. Instead of or in addition to the resin material, the non-metallic material may include materials other than the resin material. The sliding member 90 is disposed between the sprocket support body 28 and the second ratchet member 82 in the axial direction D2 parallel to the rotation center axis A1. The second ratchet member 82 is disposed between the first ratchet member 80 and the slide member 90 in the axial direction D2. The sliding member 90 preferably comprises a non-metallic material. The sliding member 90 made of non-metallic material reduces noise during operation of the bicycle rear hub assembly 12 . In this embodiment, the non-metallic material includes a resin material. Instead of or in addition to the resin material, the non-metallic material may include materials other than the resin material. The sprocket support body 28 includes an abutment 28E to abut the second ratchet member 82 to limit axial movement of the second ratchet member 82 away from the hub body 36 . The abutment 28E may indirectly abut the second ratchet member 82 in this embodiment via the slide member 90 . Alternatively, abutment 28E may directly abut second ratchet member 82 . The first ratchet member 80 is arranged on the opposite axial side of the second ratchet member 82 from the abutment 28E of the sprocket support body 28 in the axial direction D2. The sliding member 90 is disposed between the abutment 28E of the sprocket support body 28 and the second ratchet member 82 in the axial direction D2. As seen in FIG. 44 , an additional biasing member 92 is disposed between the hub body 36 and the second ratchet member 82 in the axial direction D2 to bias the second ratchet member 82 toward the sprocket support body 28 . In this embodiment, the additional biasing member 92 biases the second ratchet member 82 in the axial direction D2 via the support member 88 . Additional biasing member 92 is disposed radially outward from biasing member 84 . The additional biasing member 92 is disposed radially outward from the second plurality of ratchet teeth 82A in this embodiment. The storage member 94 includes a non-metallic material. The receiving member 94 made of a non-metallic material prevents the biasing member 84 from excessive twisting during operation of the bicycle rear hub assembly 12 . In this embodiment, the non-metallic material includes a resin material. Instead of or in addition to the resin material, the non-metallic material may include materials other than the resin material. The storage member 94 includes an axial storage portion 96 and a radial storage portion 98 . The axial receiving portion 96 is disposed between the first ratchet member 80 and the biasing member 84 in the axial direction D2. The radial receiving portion 98 extends from the axial receiving portion 96 in the axial direction D2. The radial receiving portion 98 is disposed radially inwardly from the biasing member 84 . The axial receiving portion 96 and the radial receiving portion 98 are provided integrally with each other as a one-piece unitary member. However, the axial receiving portion 96 may be a separate component from the radial receiving portion 98 . As seen in FIG. 44 , the bicycle rear hub assembly 12 includes a sealing structure 100 . The sealing structure 100 is disposed between the sprocket support body 28 and the hub body 36 . The hub body 36 includes an interior space 102 . Each of the sprocket support body 28 , the biasing member 84 , the first ratchet member 80 , and the second ratchet member 82 are at least partially disposed within the interior space 102 of the hub body 36 . The inner space 102 is sealed by the sealing structure 100 . In this embodiment, no lubricant is disposed in the interior space 102 . However, the bicycle rear hub assembly 12 may include a lubricant disposed within the interior space 102 . Compared to the case where the bicycle rear hub assembly 12 may contain lubricant disposed in the interior space 102, if no lubricant is provided, each gap between components disposed in the interior space 102 may be reduced. The operation of the bicycle rear hub assembly 12 will be described in detail below with reference to FIGS. 44 , 48 and 49 . As seen in FIG. 44 , the axial direction D2 includes a first axial direction D21 and a second axial direction D22 opposite to the first axial direction D21 . A biasing force F5 is applied from the biasing member 84 to the receiving member 94 in the first axial direction D21. The biasing force F5 of the biasing member 84 biases the receiving member 94 , the first ratchet member 80 , the second ratchet member 82 , and the slide member 90 toward the sprocket support body 28 in the first axial direction D21 . This engages the first ratchet tooth 80A with the second ratchet tooth 82A. Furthermore, as seen in FIG. 48 , when the pedaling torque T1 is input to the sprocket support body 28 in the transmission rotation direction D11 , the helical inner spline teeth 80H1 are opposed by the helical outer spline teeth 46 in the first axial direction D21 . The sprocket support body 28 guides. This strongly engages the first ratchet tooth 80A with the second ratchet tooth 82A. In this state, the pedaling torque T1 is transmitted from the sprocket support main body 28 to the hub main body 36 ( FIG. 44 ) via the first ratchet member 80 and the second ratchet member 82 ( FIG. 44 ). As seen in FIG. 48, during idling, the first ratchet member 80 comes into contact with the guide portion 28G to move from the first ratchet member 80 by the rotational friction force F6 generated between the biasing member 84 (FIG. 44) and the first ratchet member 80. The two ratchet members 82 are disengaged. As seen in FIG. 49 , an idle torque T2 is applied to the hub body 36 in the drive rotation direction D11 during idle. The idle torque T2 is transmitted from the hub body 36 ( FIG. 44 ) to the first ratchet member 80 via the second ratchet member 82 ( FIG. 44 ). At this time, the helical inner spline teeth 80H1 are guided relative to the sprocket support body 28 in the second axial direction D22 by the helical outer spline teeth 46 . This moves the first ratchet member 80 relative to the sprocket support body 28 in the second axial direction D22 against the biasing force F5. Accordingly, the first ratchet member 80 moves away from the second ratchet member 82 in the second axial direction D22 , thereby causing a weaker engagement between the first ratchet teeth 80A and the second ratchet teeth 82A. This allows the second ratchet member 82 to rotate relative to the first ratchet member 80 in the transmission rotation direction D11, thereby preventing the idle torque T2 from being transmitted from the hub body 36 to the sprocket support body via the first ratchet member 80 and the second ratchet member 82 28. At this time, the first ratchet teeth 80A slide together with the second ratchet teeth 82A in the circumferential direction D1. Modification As seen in FIG. 50 , in the above-described embodiment and other modifications, the external spline teeth 40 may include grooves 40G disposed between the external spline transmission surface 48 and the external spline non-transmission surface 50 in the circumferential direction D1 . The groove 40G reduces the weight of the rear hub assembly 12 of the bicycle. As seen in FIG. 51 , in the above-described embodiments and other modifications, the inner spline teeth 64 may include grooves 64G disposed between the inner spline transmission surface 66 and the inner spline non-transmission surface 68 in the circumferential direction D1 . The groove 64G reduces the weight of the rear sprocket assembly 14 of the bicycle. In the present application, at least ten internal spline teeth may be provided indirectly to the second opening of the second sprocket, whereas in the above embodiment at least ten internal spline teeth are directly provided to the second sprockets SP3 and SP4 the second opening of each. For example, instead of providing at least ten internal spline teeth directly to the second opening of the second sprocket SP3 and/or the second sprocket SP4, at least one of the second sprockets SP3 and SP4 may be attached To a sprocket support member comprising at least ten internal spline teeth. Alternatively, instead of providing at least ten internal spline teeth directly to the second opening of the second sprocket, at least one second sprocket may be integrally formed with at least one additional sprocket comprising at least ten internal spline teeth as One-piece monolithic member. Because this second sprocket includes at least ten internal spline teeth indirectly via the sprocket support member and/or the additional sprocket, it also means that the second sprocket includes a chain configured to mate with the bicycle rear hub assembly The wheel supports at least ten internal spline teeth engaged by the main body. The bicycle rear sprocket assembly 14 can include only one first sprocket or more than two first sprockets, and the bicycle rear sprocket assembly 14 includes two first sprockets SP1 and SP2 in the above embodiment. The bicycle rear sprocket assembly 14 may only include one second sprocket or more than two second sprockets, and the bicycle rear sprocket assembly 14 includes two second sprockets SP3 and SP4 in the above embodiment. As seen in FIG. 52 , the total number of at least ten external spline teeth 40 may range from 22 to 24 in the sprocket support body 28 . For example, the total number of at least ten external spline teeth 40 may be twenty-three. The first outer pitch angle PA11 may range from 13 degrees to 17 degrees. For example, the first outer pitch angle PA11 may be 15 degrees. The second outer pitch angle PA12 may range from 28 degrees to 32 degrees. For example, the second outer pitch angle PA12 may be 30 degrees. The first outer pitch angle PA11 is half of the second outer pitch angle PA12. However, the first outer pitch angle PA11 may be different from half of the second outer pitch angle PA12. The total number of at least ten external spline teeth 40 is not limited to the above modifications and ranges. The first outer circumferential pitch angle PA11 is not limited to the above modifications and ranges. The second outer peripheral pitch angle PA12 is not limited to the above modifications and ranges. As seen in Fig. 53, in the sprocket support body 28, the sum of the radial lengths RL11 of the plurality of external spline drive surfaces 48 may range from 11 mm to 14 mm. The sum of the radial length RL11 of a plurality of external spline transmission surfaces 48 can be 12. 5 mm. The sum of the additional radial lengths RL12 may range from 26 mm to 30 mm. For example, the sum of the extra radial length RL12 can be 28. 2mm. However, the sum of the additional radial lengths RL12 is not limited to the above modifications and ranges. As seen in FIG. 54 , the total number of at least ten first torque transmitting teeth SP1T1 may range from 22 to 24 in the first torque transmitting structure SP1T of the first sprocket SP1 . For example, the total number of at least ten first torque transmitting teeth SP1T1 may be 23. However, the total number of at least ten first torque transmitting teeth SP1T1 is not limited to the above modifications and ranges. As seen in FIG. 55 , the total number of at least ten second torque transmitting teeth SP2T1 may range from 22 to 24 in the second torque transmitting structure SP2T of the first sprocket SP2 . For example, the total number of at least ten second torque transfer teeth SP2T1 may be 23. However, the total number of at least ten second torque transmitting teeth SP2T1 is not limited to the above modifications and ranges. As seen in FIG. 56 , the total number of at least ten inner spline teeth 63 of the first sprocket SP2 may range from 22 to 24 in the first sprocket SP2 . For example, the total number of at least ten inner spline teeth 63 of the first sprocket SP2 may be twenty-three. However, the total number of at least ten internal spline teeth 63 is not limited to the above modifications and ranges. As seen in FIG. 57 , the total number of at least ten inner spline teeth 64 of the second sprocket SP3 may range from 22 to 24 in the second sprocket SP3 . For example, the total number of at least ten inner spline teeth 64 of the second sprocket SP3 may be twenty-three. However, the total number of at least ten internal spline teeth 64 is not limited to the above modifications and ranges. As seen in FIG. 58 , the total number of at least ten inner spline teeth 65 of the second sprocket SP4 may range from 22 to 24 in the second sprocket SP4 . For example, the total number of at least ten inner spline teeth 65 of the second sprocket SP4 may be twenty-three. However, the total number of at least ten internal spline teeth 65 is not limited to the above modifications and ranges. As seen in FIG. 59, among the at least ten inner spline teeth 64 of the second sprocket SP3, the first inner circumferential pitch angle PA21 may range from 13 degrees to 17 degrees. For example, the first internal pitch angle PA21 may be 15 degrees. The second inner circumferential pitch angle PA22 may range from 28 degrees to 32 degrees. For example, the second internal pitch angle PA22 may be 30 degrees. The first inner circumferential pitch angle PA21 may be half of the second inner circumferential pitch angle PA22. However, the first inner circumferential pitch angle PA21 may be different from half of the second inner circumferential pitch angle PA22. The first inner circumferential pitch angle PA21 is not limited to the above modifications and ranges. The second inner circumferential pitch angle PA22 is not limited to the above modifications and ranges. As seen in FIG. 60 , in the inner spline teeth 64 of the second sprocket SP3 , the sum of the radial lengths RL21 of the plurality of inner spline drive surfaces 66 may range from 11 mm to 14 mm. For example, the sum of the radial lengths RL21 of a plurality of internal spline transmission surfaces 66 may be 12. 5 mm. However, the sum of the radial lengths of RL21 is not limited to the above modifications and ranges. The sum of the additional radial lengths RL22 may range from 26 mm to 29 mm. For example, the sum of the extra radial length RL22 is 27. 6mm. However, the sum of the additional radial lengths RL22 is not limited to this embodiment and the above range. The internal spline teeth 63 of the first sprocket SP2 and the internal spline teeth 65 of the second sprocket SP4 have the same structure as the internal spline teeth 64 of the second sprocket SP3. As seen in FIG. 61 , the internal spline teeth 76 of the sprocket support member 37 may be of the same construction as the internal spline teeth 64 of the second sprocket SP3 illustrated in FIGS. 57 , 59 and 60 . The total number of at least ten internal spline teeth 76 of the sprocket support member 37 may range from 22-24. For example, the total number of at least ten internal spline teeth 76 of the sprocket support member 37 may be twenty-three. However, the total number of at least ten internal spline teeth 76 is not limited to the above modifications and ranges. The configuration of the internal spline teeth 64 illustrated in FIG. 60 is applicable to the internal spline teeth 76 of the sprocket support member 37 . As seen in FIG. 62, the bicycle rear sprocket assembly 14 may include an additional sprocket SP13. The extra sprocket SP13 is coupled to the extra sprocket SP12 by a plurality of coupling members SP13R. The extra sprocket SP13 includes a sprocket body SP13A and at least one sprocket tooth SP13B. The sprocket main body SP13A of the additional sprocket SP13 is coupled to the sprocket main body SP12A of the additional sprocket SP12 by a plurality of coupling members SP13R. At least one sprocket tooth SP13B extends radially outward from the sprocket body SP13A. The total number of at least one sprocket SP13B is greater than the total number of at least one sprocket SP12B. Preferably, the total number of teeth of at least one sprocket SP13B is equal to or greater than 46. More preferably, the total number of teeth of at least one sprocket SP13B is equal to or greater than 50. For example, the total number of teeth of at least one sprocket SP13B is 54. The tooth profiles of the sprocket teeth SP1B to SP13B of the sprockets SP1 to SP13 may have conventional tooth profiles and/or narrow and wide tooth profiles. In particular, as a narrow-wide tooth profile, the sprocket teeth SP1B to SP13B of the sprockets SP1 to SP13 may also comprise at least one first tooth and at least one second tooth each having a first axial maximum The chain engagement width, each of the second teeth has a second axial maximum chain engagement width smaller than the first axial maximum chain engagement width. The maximum chain engagement width in the first axis and the maximum chain engagement width in the second axis are measured along the axial direction D2. The maximum chain engagement width in the first axial direction is greater than the axial inner chain space defined by a pair of inner chain plates of the bicycle chain 20, and smaller than the axial outer chain space defined by one of the outer chain plates of the bicycle chain 20, wherein when the bicycle chain When 20 is engaged with one of the sprockets SP1 to SP13, the outer link plates face each other in the axial direction D2. The second axial maximum chain engagement width is smaller than the axial inner chain space defined by the pair of inner chain plates of the bicycle chain 20 . Therefore, at least one first tooth is configured to engage with one of the outer link plates of the bicycle chain 20, which faces in the axial direction D2 when the bicycle chain 20 is engaged with one of the sprockets SP1 to SP13. each other, and at least one second tooth is configured to engage with a pair of inner link plates of the bicycle chain 20, wherein the pair of inner link plates face each other in the axial direction D2. Preferably, at least one first tooth and at least one second tooth are arranged alternately on the outer periphery of at least one of the sprockets SP1 to SP13. Preferably, the sprocket teeth SP1B to SP13B of the sprockets SP1 to SP13 include a plurality of first teeth and a plurality of second teeth, and each of the first teeth has the above-mentioned first axial maximum chain engagement width , each of the second teeth has the above-mentioned second axial maximum chain engagement width. Preferably, the plurality of first teeth and the plurality of second teeth are arranged alternately on the outer periphery of at least one of the sprockets SP1 to SP13. Preferably, the sprocket teeth of the largest sprocket can have this narrow and wide tooth profile. Therefore, preferably, the sprocket tooth SP12B of the sprocket SP12 in FIG. 6 or the sprocket SP13B of the sprocket SP13 in FIG. 62 includes at least one of the above-mentioned first axial maximum chain engagement widths. A first tooth and at least one second tooth having the above-mentioned second axial maximum chain mesh width. As used herein, the term "comprises" and its derivatives are intended to specify the presence of stated features, elements, components, groups, integers and/or steps but not to exclude other unstated features, elements, components, groups, integers and Open term for the existence of / or steps. This concept also applies to words of similar meaning, such as the terms "having", "including" and their derivatives. The terms "member", "section", "portion", "part", "element", "body" and "structure" when used in the singular can have the dual meaning of a single part or a plurality of parts. The ordinal numbers such as "first" and "second" described in this application are only identifiers and do not have any other meaning, such as a specific order or the like. Furthermore, for example, the term "first element" does not imply the existence of a "second element" by itself, and the term "second element" does not imply the existence of a "first element" by itself. The term "pair" as used herein may encompass configurations in which paired elements have different shapes or structures from each other, in addition to configurations in which paired elements have the same shape or structure as each other. Accordingly, the terms "a", "one or more" and "at least one" are used interchangeably herein. Finally, terms of degree such as "substantially", "approximately" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. All numerical values described in this application can be understood to include terms such as "substantially", "approximately" and "approximately". Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

10: Bicycle drive system 12:Bicycle rear hub assembly 14:Bicycle rear sprocket assembly 16: Bicycle brake rotor 18: crank assembly 20: Bike chain 22: crankshaft 24: Right crank arm 26: Left crank arm 27: Front sprocket 28: Sprocket support body 28A: Internal thread part 28B: first axial end 28C: second axial end 28D: Axial sprocket abutment surface 28E: Adjacent parts 28G: Guide part 28H: The first helical spline 28I: hub indicator 28P: External Perimeter Surface 30: hub shaft 30A: shaft through hole 30B: first shaft end 30B1: First axial frame abutment surface 30C1: Second Axial Frame Adjacent Surface 30C: second shaft end 30X: shaft tube 30Y: first axis part 30Z: Second axis part 32: Locking member 32A: Tubular body 32A1: Internal Perimeter Surface 32B: external thread part 32C: Radial protrusions 32D: first axial end 32E: second axial end 32F: Tool engaging part 32G: Engagement groove 34: Brake rotor support body 36: Hub main body 36A: The first spoke installation part 36A1: First attachment hole 36B: Second spoke installation part 36B1: Second attachment hole 36C: the outermost part of the first axis 36D: the outermost part of the second axis 36F: connection hole 36H: Free wheel housing 36R: Groove 36S: Internal peripheral surface 36T: first tooth 37: sprocket support member 37A: Adhesive 38: spacer 38A: first spacer 38B: second spacer 38C: third spacer 38D: fourth spacer 38E: fifth spacer 38F: sixth spacer 38G: seventh spacer 39A: First ring 39B: Second ring 40: External spline teeth 40A: Radial outermost end 40G: Groove 40X: External spline teeth 41: Base support 42: Larger diameter part 42A: axial end 44: Flange 46: Helical external spline teeth 48: External spline drive surface 48A: Radial outermost edge 48B: Radial innermost edge 50: External spline non-drive surface 50A: Radial outermost edge 50B: Radial innermost edge 50R: Reference point 52: Extra external spline teeth 54: Additional Base Supports 60: hub engaging part 62: Support arm 62A: first attachment part 62B: Second attachment part 62C: Third attachment part 62D: Fourth attachment part 62E: Fifth attachment part 62F: Sixth attachment part 62G: Seventh attachment part 62H: Eighth attachment part 63: The first torque transmission tooth 64: Internal spline teeth 64A: Radial innermost end 64G: Groove 65: Internal spline teeth 66: Internal spline drive surface 66A: Radial outermost edge 66B: Radial innermost edge 68: Internal spline non-drive surface 68A: Radial outermost edge 68B: Radial innermost edge 68R: Reference point 76: Internal spline teeth 78: Free wheel structure 79A: First bearing 79B:Second bearing 80: first ratchet member 80A: 1st ratchet tooth 80H: Second helical spline 80H1: Helical internal spline teeth 80S: axial surface 82: second ratchet member 82A: second ratchet teeth 82E: hub main body engaging part 82P: External Perimeter Surface 82S: axial surface 82T:Protrusion 84: Offset member 84A: curly body 84B: Connecting end 86: spacer 86A: middle part 86B: Connection part 88: Support member 90: sliding member 92: Extra offset member 94: storage components 96:Axial storage part 98: radial storage part 100: sealed structure 102: Internal space A1: Central axis AG11: First external spline surface angle AG12: Second external spline surface angle AG21: First internal spline surface angle AG22: Second internal spline surface angle AG28: obtuse angle AL1: first axial length AL2: second axial length AL3: Axial length of sprocket arrangement AL4: Extra axial length AL5: Larger diameter axial length BD1: Minimum inner diameter BD2: Maximum outer diameter BD3: Minimum outer diameter BF: Bike Frame BF1: First frame BF2: Second Frame BF11: First Groove BF12: Part 1 BF21: Second groove BF22: Part Two CL1: reference line CL2: Reference line CP1: circle center point CP2: circle center point CPL: axial center plane D1: Circumferential direction D11: Transmission rotation direction D12: reverse direction of rotation D2: axial direction D21: The first axial direction D22: Second axial direction DM11: Top diameter of external spline DM12: Bottom diameter of external spline DM13: outer diameter DM14: Extra external spline top diameter DM21: Internal spline top diameter DM22: Bottom diameter of internal spline ED1: First outer diameter ED2: second outer diameter ED3: axial width ED4: axial length F1: transmission rotational force F2: Thrust F3: Thrust F5: bias force F6: Rotational friction III-III: Line L11: first radial line L12: second radial line L21: first radial line L22: second radial line MD1: first minimum diameter MD2: first minimum diameter MD3: second smallest diameter MD4: second smallest diameter MD28: Minimum outer diameter MW1: the maximum width of the circumference MW2: the maximum width of the circumference PA11: First outer pitch angle PA12: second outer pitch angle PA21: First internal pitch angle PA22: second internal pitch angle PC1: pitch circle PC2: pitch circle PC3: pitch circle PC4: pitch circle PC5: pitch circle PC6: pitch circle PC7: pitch circle PC8: pitch circle PC9: pitch circle PC10: pitch circle PC11: pitch circle PC12: pitch circle PCD1: pitch circle diameter PCD2: pitch circle diameter PCD3: pitch circle diameter PCD4: pitch circle diameter PCD5: pitch circle diameter PCD6: pitch circle diameter PCD7: pitch circle diameter PCD8: pitch circle diameter PCD9: pitch circle diameter PCD10: pitch circle diameter PCD11: pitch circle diameter PCD12: pitch circle diameter RC11: First reference circle RC12: external spline root circle RC21: Second reference circle RC22: Internal spline root circle RL11: radial length RL12: Extra radial length RL21: radial length RL22: Extra radial length SK1: first spoke SK2: Second spoke SL1: Axial spline tooth length SP1: 1st sprocket SP1A: Sprocket body SP1B: sprocket teeth SP1G: First to medial SP1H: First to the outside SP1I: Sprocket Indicator SP1K: First opening SP1T: First Torque Transfer Structure SP1T1: First torque transmission tooth SP2: 1st sprocket SP2A: Sprocket body SP2B: sprocket teeth SP2F1: first translocation-facilitating region SP2F2: Second translocation-promoting region SP2G: First to the outside SP2H: First to the inside SP2K: First Opening SP2M: First Torque Transfer Structure SP2R1: first shift facilitates groove SP2R2: second translocation-facilitating groove SP2T: Second Torque Transfer Structure SP2T1: Second torque transmission tooth SP3: Second sprocket SP3A: Sprocket body SP3B: sprocket teeth SP3F1: first translocation-promoting region SP3F2: Second translocation-promoting region SP3K: Second opening SP3R1: first shift facilitates groove SP3R2: Second translocation-facilitating groove SP4: Second sprocket SP4A: Sprocket body SP4B: sprocket teeth SP4F1: first translocation-promoting region SP4F2: Second translocation-promoting region SP4K: Second opening SP4R1: first shift facilitates groove SP4R2: second translocation-facilitating groove SP5: Extra sprockets SP5A: Sprocket body SP5B: sprocket teeth SP5F1: the first translocation-promoting region SP5F2: Second translocation-promoting region SP5R1: first shift facilitates groove SP5R2: Second translocation-facilitating groove SP6: Extra sprockets SP6A: Sprocket body SP6B: sprocket teeth SP6F1: first translocation-facilitating region SP6F2: Second translocation-promoting region SP6R1: first shift facilitates groove SP6R2: Second shift-facilitating groove SP7: Extra sprockets SP7A: Sprocket body SP7B: sprocket teeth SP7F1: the first translocation-facilitating region SP7F2: Second translocation-promoting region SP7R1: first shift facilitates groove SP7R2: Second translocation-facilitating groove SP8: Extra sprockets SP8A: Sprocket body SP8B: sprocket teeth SP8F1: first translocation facilitation region SP8F2: Second translocation-promoting region SP8R1: First Shift Facilitation Groove SP8R2: Second shift-facilitating groove SP9: Extra sprockets SP9A: Sprocket body SP9B: sprocket teeth SP9F1: the first translocation-promoting region SP9F2: Second translocation-promoting region SP9R1: First shift facilitates groove SP9R2: second translocation-facilitating groove SP10: Extra sprockets SP10A: Sprocket body SP10B: sprocket teeth SP10F1: first translocation facilitation region SP10F2: Second translocation-facilitating region SP10R1: First Shift Facilitation Groove SP10R2: Second Shift Facilitation Groove SP11: Extra sprockets SP11A: Sprocket body SP11B: sprocket teeth SP11F1: first translocation facilitation region SP11F2: Second translocation-promoting region SP11R1: First Shift Facilitation Groove SP11R2: Second Shift Facilitation Groove SP12: Extra sprockets SP12A: Sprocket body SP12B: sprocket teeth SP12F1: first translocation facilitation region SP12F2: Second translocation-promoting region SP12R1: First Shift Facilitation Groove SP12R2: Second Shift Facilitation Groove SP13: Extra sprockets SP13A: Sprocket body SP13B: sprocket teeth SP13R: Coupling member T1: pedaling torque T2: idle torque TD12: Maximum tooth tip diameter WS: wheel fastening structure WS1: fastening rod XLV-XLV: line

A more complete appreciation of the invention, and its many attendant advantages, will be readily obtained, as well as become better understood, by reference to the following embodiments when considered in conjunction with the accompanying drawings. FIG. 1 is a schematic diagram of a bicycle transmission system according to an embodiment. FIG. 2 is an exploded perspective view of the bicycle drivetrain illustrated in FIG. 1. FIG. Fig. 3 is a cross-sectional view of the bicycle transmission system taken along line III-III of Fig. 2 . 4 is a perspective view of the bicycle rear hub assembly of the bicycle drivetrain illustrated in FIG. 2 with the locking member of the bicycle rear sprocket assembly. FIG. 5 is a side view of the bicycle rear sprocket assembly of the bicycle drivetrain illustrated in FIG. 1. FIG. FIG. 6 is an enlarged cross-sectional view of the bicycle drivetrain illustrated in FIG. 4. FIG. FIG. 7 is a side view of a sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. FIG. 8 is a side view of a sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. FIG. 9 is a side view of a sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. 10 is a side view of the first sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. 11 is a side view of a sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. FIG. 12 is a side view of a sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. 13 is a side view of a sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. FIG. 14 is a side view of a sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. 15 is a side view of a sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. FIG. 16 is a side view of a sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. 17 is a side view of a sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. 18 is a side view of a sprocket of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. FIG. 19 is an exploded perspective view of the bicycle rear sprocket assembly illustrated in FIG. 5. FIG. 20 is a perspective view of the sprocket support body of the bicycle rear sprocket assembly illustrated in FIG. 4 . 21 is another perspective view of the sprocket support body of the bicycle rear hub assembly illustrated in FIG. 4 . 22 is a rear view of the sprocket support body of the bicycle rear hub assembly illustrated in FIG. 4 . 23 is a side view of the sprocket support body of the bicycle rear hub assembly illustrated in FIG. 4 . Fig. 24 is a side view of the sprocket supporting body of the bicycle rear hub assembly according to the modification. Figure 25 is an enlarged cross-sectional view of the sprocket support body illustrated in Figure 23. 26 is a cross-sectional view of the sprocket support body illustrated in FIG. 23 . FIG. 27 is a perspective view of the bicycle rear hub assembly illustrated in FIG. 4. FIG. FIG. 28 is a side view of the bicycle rear hub assembly illustrated in FIG. 4. FIG. FIG. 29 is a rear view of the bicycle rear hub assembly illustrated in FIG. 4. FIG. 30 is an exploded perspective view of the sprocket support body and a plurality of spacers of the bicycle rear hub assembly illustrated in FIG. 4 . FIG. 31 is an enlarged partial cross-sectional view of the bicycle transmission system illustrated in FIG. 4. FIG. Figure 32 is another side view of the sprocket illustrated in Figure 8 . Figure 33 is a side view of the sprocket illustrated in Figure 9 . Figure 34 is a side view of the sprocket illustrated in Figure 9 according to a modification. FIG. 35 is an enlarged cross-sectional view of the sprocket illustrated in FIG. 29. FIG. FIG. 36 is another cross-sectional view of the sprocket illustrated in FIG. 29 . FIG. 37 is another cross-sectional view of the bicycle drivetrain illustrated in FIG. 2 . FIG. 38 is an exploded perspective view of the sprocket illustrated in FIGS. 7 and 8 . 39 is another exploded perspective view of the sprocket illustrated in FIGS. 7 and 8 . FIG. 40 is an exploded perspective view of a portion of the bicycle rear hub assembly illustrated in FIG. 4. FIG. FIG. 41 is an exploded perspective view of a portion of the bicycle rear hub assembly illustrated in FIG. 40. FIG. FIG. 42 is an exploded perspective view of a portion of the bicycle rear hub assembly illustrated in FIG. 40. FIG. FIG. 43 is an exploded perspective view of a portion of the bicycle rear hub assembly illustrated in FIG. 40. FIG. FIG. 44 is a partial cross-sectional view of the bicycle rear hub assembly illustrated in FIG. 40. FIG. Fig. 45 is a cross-sectional view of the bicycle rear hub assembly taken along line XLV-XLV in Fig. 44 . FIG. 46 is a perspective view of a spacer between the bicycle rear hub assembly illustrated in FIG. 40. FIG. FIG. 47 is another perspective view of the spacer between the bicycle rear hub assembly illustrated in FIG. 40. FIG. Fig. 48 is a schematic diagram showing the action (stepping) of the first ratchet member and the sprocket supporting body of the bicycle rear hub rear assembly illustrated in Fig. 40 . Fig. 49 is a schematic view showing the function (idling) of the first ratchet member and the sprocket supporting body of the bicycle rear hub assembly illustrated in Fig. 40 . Fig. 50 is an enlarged cross-sectional view of a sprocket supporting body according to a modification. Fig. 51 is an enlarged sectional view of a sprocket according to a modification. Fig. 52 is a side view of the sprocket supporting body of the bicycle rear hub assembly according to the modification. FIG. 53 is an enlarged cross-sectional view of the sprocket support body illustrated in FIG. 52. FIG. Fig. 54 is an exploded perspective view of a sprocket of the bicycle rear sprocket assembly according to a modification. Fig. 55 is another exploded perspective view of the sprocket of the bicycle rear sprocket assembly according to the modification. Fig. 56 is a side view of the sprocket of the bicycle rear sprocket assembly according to the modification. Fig. 57 is a side view of the sprocket of the bicycle rear sprocket assembly according to the modification. Fig. 58 is a side view of the sprocket of the bicycle rear sprocket assembly according to the modification. Figure 59 is a side view of the sprocket illustrated in Figure 57. FIG. 60 is an enlarged cross-sectional view of the sprocket illustrated in FIG. 57. FIG. Fig. 61 is a partial side view of a sprocket support member of a bicycle rear sprocket assembly according to a modification. Fig. 62 is a cross-sectional view of a bicycle transmission system according to a modification.

10: Bicycle drive system

14: Bicycle rear sprocket assembly

28: Sprocket support body

28A: Internal thread part

28B: first axial end

28C: second axial end

28D: Axial sprocket abutment surface

30: hub shaft

30B: first shaft end

30B1: First axial frame abutment surface

32: locking member

32A: Tubular body

32B: external thread part

32C: Radial protrusions

32D: first axial end

32E: second axial end

36: Hub main body

36A: The first spoke installation part

37: sprocket support member

37A: Adhesive

38A: first spacer

38B: second spacer

38C: third spacer

38D: fourth spacer

38E: fifth spacer

38F: sixth spacer

38G: seventh spacer

39A: First ring

39B: Second ring

42: Larger diameter part

42A: axial end

44: Flange

60: hub engagement part

62: Support arm

62A: first attachment part

62B: Second attachment part

62C: Third attachment part

62D: Fourth attachment part

62E: Fifth attachment part

62F: Sixth attachment part

62G: Seventh attachment part

78: Free wheel structure

79A: First bearing

79B:Second bearing

A1: Central axis

AL3: Axial length of sprocket arrangement

AL4: Extra axial length

AL5: Larger diameter axial length

CPL: axial center plane

SP1: 1st sprocket

SP1G: First to medial

SP1H: First to the outside

SP2: 1st sprocket

SP3: Second sprocket

SP4: Second sprocket

SP5: Extra sprockets

SP6: Extra sprockets

SP7: Extra sprockets

SP8: Extra sprockets

SP9: Extra sprockets

SP10: Extra sprockets

SP11: Extra sprockets

SP12: Extra sprockets

Claims (58)

A bicycle rear sprocket assembly configured to be mounted to a sprocket support body of a bicycle rear hub assembly, the bicycle rear sprocket assembly comprising: A plurality of bicycle sprockets comprising: A first sprocket comprising: a first opening having a first minimum diameter that is smaller than a minimum outer diameter of the sprocket support body of the bicycle rear hub assembly; and a second sprocket comprising: a second opening having a second minimum diameter equal to or greater than the minimum outer diameter of the sprocket support body of the bicycle rear hub assembly; and At least ten internal spline teeth configured to engage the sprocket support body of the bicycle rear hub assembly. Such as the bicycle rear sprocket assembly of claim 1, which further includes A locking member comprising: a tubular body extending through the first opening of the first sprocket in a state in which the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly, the tubular body comprising: a first axial end; and a second axial end opposite to the first axial end in an axial direction with respect to a central axis of rotation of the bicycle rear sprocket assembly after the bicycle rear sprocket assembly is mounted to the bicycle In the state of the hub assembly, the first axial end is positioned closer to an axial center plane of the bicycle rear hub assembly than the second axial end; An externally threaded portion provided to the first axial end for interfacing with the sprocket support main body of the bicycle rear hub assembly in the state where the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly an internally threaded portion engages; and a radial protrusion extending radially outward from the second axial end with respect to the central axis of rotation to constrain the second sprocket assembly in the state in which the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly An axial movement of a sprocket relative to the sprocket support body of the bicycle rear hub assembly. Such as the bicycle rear sprocket assembly of claim 2, wherein The first sprocket includes: a first to the inside; and a first outward facing in the axial direction opposite the first inner facing, and The radial protrusion is configured to abut the first sprocket in the first outward side. Such as the bicycle rear sprocket assembly of claim 1, wherein The second sprocket is adjacent to the first sprocket in an axial direction relative to a central axis of rotation of the bicycle rear sprocket assembly without another sprocket between the first sprocket and the second sprocket a sprocket. Such as the bicycle rear sprocket assembly of claim 1, wherein The first sprocket includes: a first to the inside; and a first outward facing direction opposite the first inward facing in an axial direction with respect to a central axis of rotation of the bicycle rear sprocket assembly, and The first sprocket includes a first torque transmitting structure provided to the first inward side to directly or indirectly transmit a pedaling torque to the sprocket support body. Such as the bicycle rear sprocket assembly of claim 5, wherein The first torque transmitting structure includes at least ten first torque transmitting teeth. Such as the bicycle rear sprocket assembly of claim 6, wherein The total number of one of the at least ten first torque transmitting teeth is equal to or greater than twenty. Such as the bicycle rear sprocket assembly of claim 1, wherein A total number of one of the at least ten internal spline teeth of the second sprocket is equal to or greater than twenty. Such as the bicycle rear sprocket assembly of claim 8, wherein The total number of the at least ten internal spline teeth of the second sprocket is equal to or greater than twenty-eight. Such as the bicycle rear sprocket assembly of claim 1, wherein The at least ten internal spline teeth of the second sprocket have a first internal pitch angle and a second internal pitch angle different from the first internal pitch angle. Such as the bicycle rear sprocket assembly of claim 1, wherein At least one of the at least ten internal spline teeth of the second sprocket has a first spline shape different from one of the other of the at least ten internal spline teeth Second spline shape. Such as the bicycle rear sprocket assembly of claim 1, wherein At least one of the at least ten internal spline teeth of the second sprocket has a first spline size different from one of the other of the at least ten internal spline teeth Second spline size. Such as the bicycle rear sprocket assembly of claim 1, wherein A total number of teeth of one of the first sprockets is equal to or less than 10. Such as the bicycle rear sprocket assembly of claim 1, wherein The first sprocket is the smallest sprocket in the bicycle rear sprocket assembly. Such as the bicycle rear sprocket assembly of claim 1, which further includes a sprocket support member comprising at least ten internal spline teeth configured to engage the sprocket support body of the bicycle rear hub assembly, wherein The plurality of bicycle sprockets includes an additional sprocket configured to attach to the sprocket support member. Such as the bicycle rear sprocket assembly of claim 15, wherein One of the additional sprockets has a total number of teeth equal to or greater than 46. Such as the bicycle rear sprocket assembly of claim 15, wherein One of the additional sprockets has a total number of teeth equal to or greater than 50. Such as the bicycle rear sprocket assembly of claim 1, wherein the plurality of bicycle sprockets includes a plurality of second sprockets provided as the second sprocket, and Each of the plurality of second sprockets includes the at least ten internal spline teeth configured to engage the sprocket support body of the bicycle rear hub assembly. Such as the bicycle rear sprocket assembly of claim 18, which further includes a sprocket support member comprising at least ten internal spline teeth configured to engage the sprocket support body of the bicycle rear hub assembly, wherein The plurality of bicycle sprockets includes an additional sprocket configured to attach to the sprocket support member. Such as the bicycle rear sprocket assembly of claim 1, wherein The total number of one of the plurality of bicycle sprockets is equal to or greater than ten. Such as the bicycle rear sprocket assembly of claim 1, wherein The total number of one of the plurality of bicycle sprockets is equal to or greater than 11. Such as the bicycle rear sprocket assembly of claim 1, wherein The total number of one of the plurality of bicycle sprockets is equal to or greater than twelve. Such as the bicycle rear sprocket assembly of claim 1, wherein the plurality of bicycle sprockets includes an additional sprocket having a largest tooth tip diameter, the at least ten internal spline teeth of the second sprocket have an internal spline top diameter, and The ratio of the internal spline crown diameter to the maximum tooth tip diameter ranges from 0.15 to 0.18. Such as the bicycle rear sprocket assembly of claim 1, wherein The plurality of bicycle sprockets includes an additional sprocket comprising one of the following: at least one first displacement-facilitating region for facilitating a first displacement operation of a bicycle chain from the additional sprocket to an adjacent smaller sprocket; and At least one second displacement facilitating region for facilitating a second displacement operation of the bicycle chain from the adjacent smaller sprocket to the additional sprocket. Such as the bicycle rear sprocket assembly of claim 3, wherein The tubular body has a first outer diameter equal to or less than 27 mm. Such as the bicycle rear sprocket assembly of claim 25, wherein The first outer diameter is equal to or greater than 26 mm. Such as the bicycle rear sprocket assembly of claim 3, wherein The radial protrusion has a second outer diameter equal to or less than 32 mm. Such as the bicycle rear sprocket assembly of claim 27, wherein The second outer diameter is equal to or greater than 30 mm. Such as the bicycle rear sprocket assembly of claim 3, wherein The locking member has a tool engaging portion. Such as the bicycle rear sprocket assembly of claim 1, wherein The plurality of bicycle sprockets includes: a plurality of first sprockets provided as the first sprocket, each of the plurality of first sprockets including the first opening; and A plurality of second sprockets provided as the second sprocket, the plurality of second sprockets each including the second opening and the sprocket support body configured to engage the rear hub assembly of the bicycle At least ten internal spline teeth. Such as the bicycle rear sprocket assembly of claim 15, wherein The additional sprocket is attached to the sprocket support member by adhesive. Such as the bicycle rear sprocket assembly of claim 15, wherein The sprocket supporting member is made of a non-metallic material including a resin material. Such as the bicycle rear sprocket assembly of claim 1, wherein At least two of the at least ten internal spline teeth of the second sprocket are circumferentially disposed at a first internal circumferential pitch angle relative to a central axis of rotation of the bicycle rear sprocket assembly, and The first internal pitch angle ranges from 5 degrees to 36 degrees. Such as the bicycle rear sprocket assembly of claim 33, wherein The first internal pitch angle ranges from 10° to 20°. Such as the bicycle rear sprocket assembly of claim 34, wherein The first inner circumferential pitch angle is equal to or less than 15 degrees. Such as the bicycle rear sprocket assembly of claim 33, wherein At least two other internal spline teeth of the at least ten internal spline teeth of the second sprocket are circumferentially disposed at a second internal circumferential pitch angle relative to the central axis of rotation, and The second inner circumferential pitch angle is different from the first inner circumferential pitch angle. Such as the bicycle rear sprocket assembly of claim 1, wherein The at least ten internal spline teeth of the second sprocket have an internal spline crown diameter equal to or less than 34 mm. Such as the bicycle rear sprocket assembly of claim 37, wherein The inner spline top diameter of the second sprocket is equal to or smaller than 33 mm. Such as the bicycle rear sprocket assembly of claim 37, wherein The inner spline top diameter of the second sprocket is equal to or greater than 29 mm. Such as the bicycle rear sprocket assembly of claim 1, wherein The at least ten internal spline teeth of the second sprocket have an internal spline base diameter equal to or less than 32 mm. Such as the bicycle rear sprocket assembly of claim 40, wherein The internal spline base diameter is equal to or less than 31 mm. Such as the bicycle rear sprocket assembly of claim 40, wherein The internal spline base diameter is equal to or greater than 28 mm. Such as the bicycle rear sprocket assembly of claim 1, wherein the at least ten internal spline teeth include a plurality of internal spline drive surfaces for receiving drive rotational force from a rear hub assembly of the bicycle during pedaling, Each of the plurality of internal splined drive surfaces includes a radially outermost edge, a radially innermost edge, and a radial length defined from the radially outermost edge to the radially innermost edge, and The sum of one of the radial lengths of the plurality of internal spline drive surfaces is equal to or greater than 7 mm. Such as the bicycle rear sprocket assembly of claim 43, wherein The sum of the radial lengths is equal to or greater than 10 mm. Such as the bicycle rear sprocket assembly of claim 43, wherein The sum of the radial lengths is equal to or greater than 15 mm. Such as the bicycle rear sprocket assembly of claim 43, wherein The sum of the radial lengths is equal to or less than 36 mm. Such as the bicycle rear sprocket assembly of claim 1, wherein At least one of the at least ten internal spline teeth includes an internal splined drive surface having a first internal splined surface angle defined between the internal splined drive surface and a first radial line from the bicycle rear sprocket assembly a central axis of rotation extends to a radially outermost edge of the inner splined drive surface, and The angle of the first inner spline surface ranges from 0° to 6°. Such as the bicycle rear sprocket assembly of claim 47, wherein The at least one of the at least ten internal spline teeth includes an internal splined non-drive surface having a second internal splined surface angle defined between the internal splined non-drive surface and a second radial line from the bicycle rear sprocket the central axis of rotation of the assembly extends to a radially outermost edge of the internal splined non-drive surface, and The second inner spline surface angle ranges from 0° to 6°. Such as the bicycle rear sprocket assembly of claim 1, wherein At least one of the at least ten internal spline teeth of the second sprocket is circumferentially symmetrical with respect to a reference line extending in a radial direction relative to the central axis of rotation from the central axis of rotation to A circumferential center point of a radially outermost end of the at least one of the at least ten internal spline teeth. A bicycle transmission system comprising: Such as the bicycle rear sprocket assembly of claim 1; and A bicycle rear hub assembly, which includes: Hub shafts comprising a shaft through-bore having a minimum inner diameter equal to or greater than 13 mm; a hub body rotatably mounted on the hub axle about a central axis of rotation of the bicycle rear hub assembly; and A sprocket support body is rotatably mounted on the hub axle around the rotation center axis. Such as the bicycle transmission system of claim 50, wherein The minimum inner diameter of the shaft through hole is equal to or greater than 14 mm. Such as the bicycle transmission system of claim 50, wherein The minimum inner diameter of the shaft through hole is equal to or smaller than 21 mm. Such as the bicycle rear sprocket assembly of claim 6, wherein The total number of one of the at least ten first torque transmission teeth ranges from 22 to 24. Such as the bicycle rear sprocket assembly of claim 1, wherein A total number of the at least ten internal spline teeth of the second sprocket ranges from 22-24. Such as the bicycle rear sprocket assembly of claim 33, wherein The first internal pitch angle ranges from 13 degrees to 17 degrees. Such as the bicycle rear sprocket assembly of claim 36, wherein The second inner circumferential pitch angle ranges from 28 degrees to 32 degrees. Such as the bicycle rear sprocket assembly of claim 36, wherein The first inner circumferential pitch angle is half of the second inner circumferential pitch angle. Such as the bicycle rear sprocket assembly of claim 43, wherein The sum of the radial lengths of the plurality of internal spline drive surfaces ranges from 11 mm to 14 mm.

Images