WO1998009829A1

WO1998009829A1 - Bicycle rim assembly

Info

Publication number: WO1998009829A1
Application number: PCT/US1997/015516
Authority: WO
Inventors: Thomas W. Ritchey
Original assignee: Ritchey Designs, Inc.
Priority date: 1996-09-04
Filing date: 1997-09-04
Publication date: 1998-03-12
Also published as: AU4178897A

Abstract

A rim (10) for a bicycle includes chambers (20, 22 and 24) and dividing members (26 and 28). The spokes are mounted in holes (30 and 32) which are formed off-center in the rim.

Description

BICYCLE RIM ASSEMBLY

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an improved bicycle rim assembly, and more particularly to a rear bicycle wheel assembly which includes an offset rim arrangement and a gear assembly which accommodates an additional gear to provide a nine gear rear sprocket.

Description of the Related Art

A conventional bicycle includes a front wheel which is generally symmetrical about a plane extending through the center of the rim and perpendicular to the axis of the wheel. In the conventional front bicycle wheel, spokes are attached to the rim along the center plane of the rim and are symmetrically attached to two spaced apart flanges on a hub of the front wheel. The spokes on the left and right side of a front wheel are the same length and are tensioned to center the hub in the center of the rim. The general symmetry of the front wheel allows the left and right side spokes to be tensioned to the same degree.

A conventional rear bicycle wheel differs from the front bicycle wheel in that the rear wheel is not symmetrical about a central plane of the wheel hub. The asymmetry in the rear bicycle wheel is due to the fact that the rear wheel hub includes a set of sprockets positioned on the right side of the hub (from the viewpoint of an individual sitting on the bicycle). FIG. 1 illustrates a conventional rear bicycle wheel 100 mounted in a bicycle frame 102. As shown in FIG. 1 , the frame 102 has legs 104, 106 which are symmetrical about a center plane C of the bicycle. The rear bicycle wheel 100 includes a rim 108 which receives the tire, a hub that encircles the wheel axle, and left and right side spokes 114, 116 connected to and extending between the rim 108 and the hub. The hub of the rear wheel includes two parts, the hub shell 110 and the chain receiving drive sprockets 112 positioned on the right side of the hub. The hub shell 110 includes left and right side flanges 118, 120 which extend from the hub shell for attachment of the left and right side spokes 114, 116.

The tire (not shown) and rim 108 of the conventional rear bicycle wheel are positioned centrally between the legs 104, 106 of the frame 102 so that the central plane of the rim is aligned with the center plane C of the frame. In the conventional rear bicycle wheel, however, the longitudinal center point of the hub shell 110 between the two flanges 118, 120 is displaced from the center plane C of the bicycle frame. The displacement of the center of the hub shell 110 provides space between the right hub flange 120 and the right leg 106 of the frame 102 for the set of sprockets 112.

Therefore, in a conventional rear bicycle wheel 100, the spokes 114, 116 of the wheel are provided in two different lengths to accommodate the offset positioning of the hub shell 110. In particular, the spokes 116 on the right side of the rear wheel (i.e. , the side of the wheel located adjacent the set of sprockets 112) are shorter than the spokes 114 on the left side of the rear wheel 100. The right side spokes 116 are also closer to vertical than the left side spokes 114.

As is known in the art, the offset of the center of the hub shell 110 from the central plane C of the rim in the conventional rear bicycle wheel means that the tension in the right side spokes 116 at the sprocket side of the rear wheel 100 must be greater than the tension in the left side spokes 114 on the opposite side of the wheel. In a conventional rear bicycle wheel, the spoke tension in the right side spokes 116 is about 55 kg, which represents a typical maximum tension, while the spoke tension in the left side spokes 114 is about 30 kg to 35 kg. The spoke tension of the left side spokes 114 is generally about 30 percent to 50 percent less than the spoke tension of the right side spokes 116 for a conventional rear bicycle wheel. Although the tension differential between the left and right side spokes 114, 116 in a rear bicycle wheel is necessary to provide a stable and properly functioning rear wheel, the tension differential also presents certain disadvantages and drawbacks. Bicycle wheels are designed so that the tensioned spokes remain tensioned during use. As long as the spoke is held in tension, the spoke tensioning screw or nipple will be pressed against the inside of the rim and will be unable to unscrew. The maximum tension in any spoke should preferably be greater than any load applied to the wheel during use. When a force exceeding the tension in any spoke is applied to the wheel, such as might occur when a heavy individual is riding the bicycle or when the wheel is being traversed over rough terrain and subjected to repeated loads, the spoke will tend to momentarily unload or slacken. The momentary reduction or loss of spoke tension can cause the spoke tensioning screw or nipple which maintains the spoke tension to unscrew due to vibration. This can cause the tensioning screw or tensioning nipple on the spoke to loosen so that the tension in the spoke is reduced. A reduction in the tension in one or more of the spokes can significantly and detrimentally affect the wheel from the standpoint of strength and stability.

It is thus preferred that the tension in each spoke be as high as possible to withstand the applied forces and maintain the spokes in tension. However, there are a variety of factors that limit the amount of tension that can be applied to the spokes. These factors include rim strength, spoke strength and spoke connection strength. The 55 kg tension mentioned above that is applied to right side spokes 116 represents approximately the maximum tension that can be applied to spokes in a typical wheel, assuming the wheel is not specially designed to accommodate greater loads (e.g. , through the use of higher strength materials for the rim, higher strength materials for the spokes, etc). In addition, as also mentioned above, a tension differential must exist between the tension in the right side spokes 116 and the tension in the left side spokes 114 in order for the wheel to properly function and so the left side spokes must be subjected to a lesser tension. Thus, these lower tensioned spokes limit the maximum load that can be applied to the wheel without momentarily unloading or slackening the spokes. It can be seen, therefore, that the strength and durability of the rear bicycle wheel is necessarily limited by the amount of tension that can be applied to the lower tensioned spokes. Further, the maximum tension that can be applied to the lower tensioned spokes is necessarily limited by the geometry of the wheel and the maximum tension that can be applied to the higher tensioned spokes, the latter of which is necessarily limited by various factors such as those mentioned above.

As discussed above, a conventional rear bicycle wheel is designed so that the center of the hub shell 110 (i.e., the midpoint between the two flanges 118, 120) is displaced from the central plane C along which the spokes 114, 116 are attached to the rim 108. This displacement is called dish. A large amount of dish is undesirable because the larger the dish, the larger the spoke tension differential which is necessary to accommodate the off center forces of the hub on the rim. The dish reduces the overall strength of the rear wheel due to the tendency of the less tensioned, longer, left side spokes 114 to go slack and begin to loosen. A conventional rear bicycle wheel designed to accommodate a hub having a set of eight sprockets 112 has 6 mm of dish.

Attempts have been made to completely eliminate dish in rear bicycle wheels by varying the configuration of the rear rim to achieve a rear wheel with equal left and right spoke tensions. U.S. Patent No. 5,228,756 discloses two different rim configurations which attempt to eliminate dish from a rear bicycle wheel by mounting the spokes near the side of the rim. However, this side mounting of the spokes produces torsional forces within the rim. U.S. Patent No. 5,228,756 attempts to address the problems associated with the creation of torsional forces by using additional material to strengthen one side of the rim or by using a conically shaped rim which is brought into a cylindrical shape by tensioning of the spokes. However, in practice the two embodiments of U.S. Patent No. 5,228,756 do not result in a functional rear bicycle wheel.

Other problems which occur in bicycles include chain breakage and wear on chain engaging sprockets, both of which increase with increasing chain tension. Chain tension is determined by the leverage being applied by the crank to the teeth of the sprockets. The larger the distance between the teeth of the front sprocket or chainring and the pedal axis, or between the teeth of the rear sprocket or cog and the wheel axis of the rear sprocket, the greater the leverage and lower the chain tension. Therefore, the use of small sprockets of compact drive setups with small diameter chainrings and cogs causes higher chain tensions than larger diameter drive configurations. High chain tension leads to chain breakage due to the high stress on the chain. In addition, high chain tension increases wear on sprockets around which the chain passes. The high chain tensions which are caused by the use of the smallest sprockets on a conventional bicycle will cause the chain to break more readily and will cause greater wear on the sprockets.

SUMMARY OF THE INVENTION

The rear bicycle wheel assembly according to the present invention addresses the disadvantages of the prior art rear bicycle wheels by reducing the dish of the rear wheel and reducing the tension differential between the left and right spokes in the rear wheel. The reduction in the dish which is accomplished by the present invention provides a space in which an additional rear sprocket is accommodated, such as a ninth rear sprocket. The reduction in spoke tension differential according to the present invention, which is achieved by designing the wheel in a manner that allows the tension in the lower tensioned spokes to be increased, results in a stronger and more durable rear wheel. The system according to the present invention also addresses the disadvantages of high chain tension in known bicycles by permitting elimination of the smallest of the three sprockets of a conventional front drive setup, while at the same time providing a gear span ratio that is similar to that achieved when using the smallest of the three front sprockets.

According to one aspect of the present invention, a bicycle rear wheel includes a wheel hub having a central axis of rotation, two spoke anchoring flanges located on the hub for anchoring a plurality of spokes to the hub, a set of sprockets located on one side of the hub, and a bisecting plane extending through the hub perpendicular to the central axis of rotation at a location which is an equal distance from each of the two spoke anchoring flanges; an annular rim having two side walls and a central plane located centrally between the two side walls of the annular rim, the annular rim having a cross sectional triple box construction including three annular chambers; and a plurality of spoke anchoring points located on the annular rim along a spoke anchoring plane which is located between the bisecting plane of the hub and the central plane of the annular rim.

According to a further aspect of the present invention, a rear bicycle wheel assembly includes a wheel hub including a hub shell and a set of sprockets positioned adjacent the hub shell, the set of sprockets having a central axis of rotation coincident with a central axis of rotation of the hub shell, the hub shell having left and right side spoke attachment flanges, and the set of sprockets including a plurality of sprockets of graduated diameters with a largest of the plurality of sprockets located adjacent the hub shell; a plurality of left and right side spokes; an annular rim having the plurality of left and right side spokes attached to the annular rim along a spoke attachment plane; and said largest of the plurality of sprockets which is located adjacent the flange having a concave cross section such that a peripheral portion of the largest of the plurality of sprockets extends inward toward the spokes. According to an additional aspect of the present invention, a rim for a rear bicycle wheel includes two parallel annular side edges; a lower annular rim member connecting the annular side edges; an upper annular rim member connecting the annular side edges; two dividing members dividing a cross section of the rim into left, right, and center annular chambers, the left and right annular chambers configured to receive an attachment member for forming the rim into a continuous annular configuration; and spoke anchoring points located on the lower annular rim member along a plane which is located parallel to and displaced from a central plane of the rim.

BRIEF DESCRΠTIQN OF THE DRAWING FIGURES

The invention will be described in greater detail with reference to the accompanying drawings in which like elements bear like reference numerals, and wherein:

FIG. 1 is a schematic view of a rear bicycle wheel assembly according to the prior art; FIG. 2 is a cross sectional view of the off center rim according to the present invention; and

FIG. 3 is a schematic view of a rear bicycle wheel assembly according to the present invention.

DETAILED DESCRIPTION

In accordance with the present invention, the bicycle rear wheel rim is designed as an off center rim. The off center rim 10 according to the present invention is illustrated in cross section in FIG. 2. As shown in FIG. 2, the off center rim 10 includes parallel upstanding annular side edges 12, 14, an annular upper rim member 16, and an annular lower rim member 18. The upper and lower rim members 16, 18 extend between and connect the side edges 12, 14 of the rim. The upper surfaces of the parallel side edges 12, 14 include inwardly protruding rim edges 13, 15, respectively, which receive and retain the bicycle tire (not shown) in the known manner. The rim 10 according to the present invention has a triple box construction which includes three annular chambers including a left chamber 20, a center chamber 22, and a right chamber 24. The left and right chambers 20, 24 are smaller in cross sectional area than the center chamber 22. A left dividing member 26 divides the left chamber 20 from the center chamber 22 and a right dividing member 28 divides the center chamber 22 from the right chamber 24. The left and right dividing members 26, 28 extend from the upper rim member 16 to the lower rim member 18 and help to support and strengthen the rim 10 against torsional moments. The dividing members 28, 26 preferably have substantially uniform thicknesses throughout except for a slight increase in thickness where the dividing members join the upper and lower rim members 16, 18. The upper rim member 16 has a generally concave downward cross-section and has a substantially uniform thickness except for a slight increase in thickness where the upper rim member joins the side edges 12, 14 and the dividing members 26, 28. The lower rim member 18 is concave downward and has a thickness which increases gradually from the side edge 12 to a thickest portion 19 which is displaced from a center of the rim and then gradually decreases to the opposite side edge 14 of the rim. The thickest portion 19 of the lower rim member 18 is formed at the lowest portion of the rim.

The rim 10 is preferably formed by extruding an elongated rim member having the cross sectional triple box construction described above. This extruded rim member is then formed into the circular rim. The ends of the extruded rim member are joined together by two substantially cylindrical pins (not shown) having barbed ends which are inserted into the left chamber 20 and the right chamber 24 at each end of the extruded member. Therefore, the left and right chambers 20, 24 are sized and shaped to receive a generally cylindrical barbed pin of generally the same size.

The off center rim 10 according to the present invention has a center plane C which extends through a center of the rim parallel to the side edges 12, 14 at a midpoint between the side edges. The rim 10 includes spoke anchoring holes 30 which are formed in the lower rim member 18 at the thickest portion 19 of the lower rim member. The spoke anchoring holes 30 are spaced along the annular surface of the lower rim member 18 in a plane S which is parallel to and displaced from the center plane C of the rim. The rim 10 also includes access holes 32 which are formed in the upper rim member 16 and radially aligned with each of the spoke anchoring holes 30. The access holes 32 are provided for tensioning the spokes during assembly of the wheel.

Due to the location of the spoke anchoring holes 30 in the plane S which is displaced from the center plane C along which will act the reaction force from the ground as the wheel moves along the ground, a torsional moment is created in the rim 10 during use. The triple box construction including the right and left dividing members 26, 28 provides the necessary strength and structural support to resist torsional moments caused by the off center position of the spoke anchoring holes 30. Due to the triple box construction including the three chambers the off center rim 10 is torsionally stronger than other rim constructions. A schematic view of the rear bicycle wheel according to the present invention is illustrated in FIG. 3. The wheel assembly as illustrated in FIG. 3 includes the off center rim 10, a hub including a hub shell 36 and a set of sprockets 42, and left and right side spokes 38, 40. The hub shell 36 includes left and right side annular flanges 44, 45 extending from the hub shell at opposite ends of the hub shell. Overlaying the off center rim 10 in the schematic view FIG. 3 is a shaded portion which illustrates the cross sectional configuration of a symmetrical rim 34 for use with center mounted spokes. The symmetrical rim 34 is illustrated only for comparison to the off center rim 10 and is not a part of the present invention. The left and right side spokes 38, 40 according to the present invention are of slightly different lengths between a point where the spokes contact the rim 10 and a point where the spokes contact the respective flanges 44, 45 of the hub shell 36. In particular, the right side spokes 40 which are connected to the right side flange 45 are somewhat shorter than the left side spokes 38 which are connected to the left side flange 44. In addition, the tensions in the left and right side spokes 38, 40 differ, with the right side spokes 40 being at a higher tension than the left side spokes 38.

Although the left and right side spokes 38, 40 are of slightly different lengths, this difference in lengths is smaller than with conventional rear bicycle wheel rims. This provides a significant advantage over conventional rear bicycle wheels. Namely, since the difference in length between the spokes 38, 40 is relatively small, the same standard length spokes can be used for both sides of the of the wheel and the spokes can be adjusted differently during assembly. In contrast, in the prior art rear bicycle wheels spokes of two different standard lengths must be used for the two sides of the wheel.

According to the present invention, the right side spokes 40 have a tension which is substantially the same as the tension in the right side spokes of conventional rear bicycle wheels which is between 50 kg and 60 kg, preferably about 55 kg. However, by utilizing the off center rim construction in accordance with the present invention, dish is reduced and the tension in the left side spokes 38 can be increased to between 40 kg and 50 kg, preferably about 45 kg. This is highly advantageous in that it results in an increase in the strength and stability of the rear bicycle wheel. As mentioned earlier, the maximum tension in any spoke should be greater than any load that is applied to the wheel during use to ensure a strong and stable wheel. Thus, constructing the rear bicycle wheel of the present invention in a way that allows the spoke tension of the left side spokes 38 to be increased is advantageous because the wheel can withstand greater loads and is thus more stable and strong than conventional rear bicycle wheels.

In addition, in the wheel assembly according to the present invention, the angle between the right side spokes 40 and the wheel flange is reduced relative to the corresponding angle in a conventional rear bicycle wheel by virtue of the displacement of the spoke anchoring holes 30. Thus, the right side spokes 40 are less vertical in the present invention than in the conventional rear wheel. The smaller angle a provides space for the addition of a ninth sprocket 48 to the set of sprockets 42. Thus, the rear bicycle wheel of the present invention is further advantageous in that it permits the addition of another sprocket without having to increase the axial length of the rear wheel assembly to the extent that would otherwise be necessary. In addition, due to the smaller angle a the right side spokes 40 of the present invention are further away from possible contact with an improperly adjusted or misaligned rear derailleur (not shown).

As illustrated in FIG. 3, the rear bicycle wheel according to the present invention includes a hub shell 36 which encircles the wheel axle and has spoke anchoring protruding annular flanges 44, 45 at opposite sides thereof. The hub shell 36 has a central bore 46 through which the wheel axle (not shown) extends. A bisecting plane B extends through a center of the hub shell 36 perpendicular to the central bore 46 at a location which is an equal distance from each of the two spoke anchoring flanges 44, 45. As illustrated in FIG. 3, the plane S in which the spoke anchoring holes 30 are located in the rim 10 is between the center plane C of the rim and the bisecting plane B of the hub shell 36. Preferably, the plane S is located approximately at a midpoint between the center plane C and the bisecting plane B.

The distance of displacement D between the center plane C and the plane S for an offset bicycle rim according to the present invention is between 2 mm and 4 mm, preferably about 3 mm. The distance between the plane S and the bisecting plane B of the hub shell 36 is between 2 mm and 4 mm, preferably about 3 mm.

The displacement D of the plane S in which the spoke anchoring holes 30 are located from the center plane C reduces the dish or the offset of the hub shell 36 with respect to the rim 10. The reduction in the dish of the wheel according to the present invention extends the wheel life by allowing the spoke tension differential to be reduced through an increase in the tension of the left side spokes. The off center rim 10 allows the dish to be reduced by approximately one-half and also permits the differential in spoke tension to be reduced by the displacement of the spoke anchoring holes 30 from the center plane C to the plane S. In the conventional rear bicycle wheel the spoke tension in the lower tensioned left side spokes is between 30 percent and 50 percent less than the spoke tension in the higher tensioned right side spokes. In the present invention, the spoke tension in the lower tensioned left side spokes is between 10 percent and 25 percent, preferably about 15 percent, less than the spoke tension in the higher tensioned right side spokes.

In addition to making the wheel stronger, the reduction in dish provides space for a 9 cog set of sprockets 42 to be placed between the wheel hub shell 36 and the bicycle frame (not shown) instead of a conventional 8 cog set. The off center rim 10 according to the present invention may be used in an 18 speed bicycle which includes a front drive setup having two chainrings and a rear 9 speed cog set or sprocket 42. The front drive setup preferably includes two chainrings, such as, a 30 tooth chainring and a 42 tooth chainring, as opposed to the conventional three chainring front drive setup. With the 30 tooth chain ring as the smallest chainring, the tension in the chain according to the present invention is reduced by 30 percent compared to a conventional 24 speed bicycle including a small 22 tooth chainring. This decrease in chain tension due to the elimination of the smallest 22 tooth chainring is advantageous because it greatly increases chain life and decreases chainring and cog wear. The elimination of the smallest chainring on the front drive assembly is also advantageous as it reduces the maximum angle that the chain must traverse between the front drive assembly and the rear sprocket assembly. In spite of the elimination of the smallest chainring on the front drive assembly, the addition of the ninth sprocket on the rear sprocket assembly provides a gear span ratio that is similar to that provided by an eight sprocket rear assembly and a three chainring front assembly.

The rear 9 cog sprocket set 42 for use in the present invention includes 9 cogs which fit onto an 8-speed cassette barrel by using a separate ninth 33 tooth cog 48 which attaches onto a standard 8-speed 11 to 26 tooth cogset 50. As a space saving feature, the ninth cog 48 with 33 teeth is preferably concave or dished. The perimeter of the concave ninth cog 48 extends partially over the flange 45 of the hub shell 36 and fits between the existing 8-speed cogset 50 and the spokes of the wheel. The space for the ninth cog 48 is provided by the off center rim of the present invention which allows the right side spokes 40 to be less vertical. As illustrated in FIG. 3, the ninth cog 48 may be formed with a step 52 which provides the concavity when the cog is viewed in cross section. Alternatively, the ninth cog 52 may have a gradual concavity or dish shape without an abrupt step.

The dished shape of the ninth cog 48 allows the ninth cog to be accommodated without requiring a significant amount of additional space on the hub. For example, the addition of a ninth cog with a flat shape would require about 5 mm of additional space. By reducing the angle of the right side spokes in accordance with the present invention and utilizing a dished or concavely shaped ninth cog in accordance with the present invention, the same amount of additional space is not necessary to accommodate the ninth cog. The combination of the rear 9 cog sprocket 42 and the two chainring front drive setup (not shown) provides 17 usable gear ratios out of 18 available gears. With the conventional 24 speed bicycle there are 19 of the available 24 gears which are usable considering crossover and chain tension considerations. The 18 speeds of the present invention can achieve a similar span of gear ratios to a 24 speed bicycle. The present invention including the dished ninth cog 48 may also be used to provide a 27 speed bicycle.

The gear assembly according to the present invention which is possible due to the space provided by the off center rim configuration 10 provides significant advantages in reduced chain tension which help to extend the bicycle life. In addition, the off center rim 10 itself provides increased wheel strength and durability.

While the invention has been described in detail with reference to a preferred embodiment thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed without departing from the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A bicycle rear wheel comprising: a wheel hub having a central axis of rotation, two spoke anchoring flanges located on the hub for anchoring a plurality of spokes to the hub, a set of sprockets located on one side of the hub, and a bisecting plane extending through the hub perpendicular to the central axis of rotation at a location which is an equal distance from each of the two spoke anchoring flanges; an annular rim having two side walls and a central plane located centrally between the two side walls of the annular rim, the annular rim having a cross sectional triple box construction including three annular chambers; and a plurality of spoke anchoring points located on the annular rim along a spoke anchoring plane which is located between the bisecting plane of the hub and the central plane of the annular rim.

2. The bicycle rear wheel according to claim 1 , wherein the three annular chambers of the triple box construction includes separate left, right, and center chambers having asymmetrical cross sections.

3. The bicycle rear wheel according to claim 1, wherein the three annular chambers are each of a different cross sectional shape.

4. The bicycle rear wheel according to claim 1 , further comprising a first set of spokes and a second set of spokes, each of the spokes of the first set of spokes attached at a first end to the annular rim at the spoke anchoring points and attached at a second end to the a first of the two spoke anchoring flanges, and each of the spokes of the second set of spokes attached at a first end to the annular rim at the spoke anchoring points and attached at a second end to a second of the two spoke anchoring flanges.

5. The bicycle rear wheel according to claim 4, wherein the first set of spokes has a spoke tension which is between 10 percent and 25 percent greater than the a spoke tension of the second set of spokes.

6. The bicycle rear wheel according to claim 1 , wherein the set of sprockets includes a largest diameter sprocket having a dish shape and the first of the two spoke anchoring flanges positioned adjacent a concave surface of the dish shaped sprocket.

7. The bicycle rear wheel according to claim 1 , wherein the spoke anchoring plane is located between 2 mm and 4 mm from the bisecting plane of the hub, and the spoke anchoring plane is located between 2 mm and 4 mm from the central plane of the annular rim.

8. A rear bicycle wheel assembly comprising: a wheel hub including a hub shell and a set of sprockets positioned adjacent the hub shell, the set of sprockets having a central axis of rotation coincident with a central axis of rotation of the hub shell, the hub shell having left and right side spoke attachment flanges, and the set of sprockets including a plurality of sprockets of graduated diameters with a largest of the plurality of sprockets located adjacent the hub shell; a plurality of left and right side spokes; an annular rim having the plurality of left and right side spokes attached to the annular rim along a spoke attachment plane; and said largest of the plurality of sprockets which is located adjacent the flange having a concave cross section such that a peripheral portion of the largest of the plurality of sprockets extends inward toward the spokes.

9. The bicycle rear wheel assembly according to claim 8, wherein the annular rim has a central plane extending through a center of the rim perpendicular to an axis of the wheel, and the spoke attachment plane is displaced from the central plane of the annular rim.

10. The rear bicycle wheel assembly according to claim 9, wherein the spoke attachment plane of the annular rim is displaced from the central plane of the annular rim by between 2 mm and 4 mm.

11. The rear bicycle wheel assembly according to claim 8, wherein the spoke attachment plane of the annular rim is displaced from a bisecting plane located an equal distance from each of the flanges by between 2 mm and 4 mm.

12. The bicycle rear wheel assembly according to claim 8, wherein a spoke tension differential between the left and right side spokes is between 10 percent and 25 percent.

13. The bicycle rear wheel assembly according to claim 8, wherein the peripheral portion of largest of the plurality of sprockets extends over the right side spoke attachment flange.

14. The bicycle rear wheel assembly according to claim 8, wherein the annular rim has a triple box construction when viewed in cross section including three annular chambers of different cross sectional shapes.

15. The bicycle rear wheel assembly according to claim 8, wherein the plurality of sprockets include nine sprockets.

16. A rim for a rear bicycle wheel comprising: two parallel annular side edges; a lower annular rim member connecting the annular side edges; an upper annular rim member connecting the annular side edges; two dividing members dividing a cross section of the rim into left, right, and center annular chambers, the left and right annular chambers configured to receive an attachment member for forming the rim into a continuous annular configuration; and spoke anchoring points located on the lower annular rim member along a plane which is located parallel to and displaced from a central plane of the rim.

17. The rim according to claim 16, wherein the plane on which the spoke anchoring points are located is displaced from the central plane of the rim by between 2 mm and 4 mm.

18. The rim according to claim 16, wherein the left and right annular chambers have cross sections of different shapes.

19. The rim according to claim 16, wherein the left and right annular chambers are smaller in cross sectional area than the center annular chamber.