JP2009051412A - Pneumatic tire for two-wheeled vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for a two-wheeled vehicle, having superior abrasion resistance as well as gripping force capable of maintaining lateral gripping force even during abrasion by improving the lateral gripping force when the two-wheeled vehicle turnably travels. <P>SOLUTION: A different kind of rubber 20 with its surface exposed to a tread surface is arranged on each tread shoulder part 11a of a tread 11, located adjacently to each sidewall 12. The width of the rubber 20, along the tread surface in a tire width direction is set within a range of not less than 6% nor more than 20% of a tread developed width, and is positioned within a range of not less than 5% nor more than 25% of the tread developed width directed from the tread end 11a of the tread 11 as a boundary with the sidewall 12 to a tread center part. The rubber 20 is made of a rubber member having a lower dynamic modulus of elasticity than that of a rubber member located adjacently to the side of the tread center part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire for a two-wheeled vehicle, and more particularly to a pneumatic tire for a two-wheeled vehicle having a tread structure capable of improving a grip force during turning.

  Conventionally, pneumatic tires used for motorcycles are known. Because of the structural characteristics of a two-wheeled vehicle, the vehicle body is tilted during cornering, so the portion of the tire that touches the road surface moves due to the tilt of the vehicle body. Also, when standing upright without tilting the vehicle body, the speed is high and the braking force and driving force in the front-rear direction (the equator direction of the tire) are applied to the tire. Lateral force is actively applied. Therefore, a lateral grip force that opposes the lateral force is required for the shoulder portion of the tire. On the other hand, rubber with high wear resistance is often used at the tire width direction center portion of the tire because commercial tires have a high frequency of straight running.

  In tires used in races and competitions, the speed during straight running is very high, so rubber that does not generate heat easily is placed in the tread center part, or rubber that does not generate heat internally because the tread center part has a two-layer structure. In addition, a device has been devised such as arranging rubber with a large gripping force outside. In particular, when racing on a circuit or when driving violently on ordinary roads, the tire shoulders generate heat during driving, so the turning performance decreases with the driving, and wear of the tire shoulders progresses. The rubber will deteriorate.

On the other hand, when the dynamic elastic modulus (E ′), which is an index of the elastic modulus of rubber, is low as rubber characteristics, it means that the rubber is soft, and the soft rubber bites into the unevenness of the road surface, so the grip force is large. On the other hand, soft rubber has a characteristic of fast wear. The softness of rubber can also be indicated by hardness, that is, Shore A hardness. Rubber with a low Shore A hardness is soft and has a high grip, but has a poor wear resistance. At the same time, since deformation of the rubber is promoted, there is a characteristic that heat is easily generated due to strain energy loss caused by the viscoelastic characteristics of the rubber.
Two-wheeled vehicle tires have a characteristic of turning while tilting the vehicle body, and the tread position that touches the road surface of the tire moves depending on the inclination of the vehicle body. May be used.

For example, it is assumed that the rubber physical properties are changed at the center portion and the shoulder portion of the tire, “Pneumatic tire for motorcycle” (see Patent Document 1), “Pneumatic tire for motorcycle with spiral belt structure” (Patent Document 2). (Refer to Patent Document 3) and "Pneumatic Tire" (refer to Patent Document 3) and "Motorcycle Tire" (refer to Patent Document 4) are known as rubber property changes in the tire thickness direction. ing. These are functions in which the functions of the center portion and the shoulder portion of the tire are separated.
JP 2000-158910 A JP-A-7-108805 JP 2006-76355 A JP 2005-271760 A

  By the way, in a pneumatic tire for a two-wheeled vehicle, the two-wheeled vehicle tilts the vehicle body when turning, so the place where the tire tread is in contact with the road surface differs between straight traveling and turning. That is, there is a feature that the tread center portion is used during straight traveling and the tread end portion is used during turning. In races and competitions, lateral grip is particularly important when turning. If the side grip force is sufficient when turning, not only can you pass through the corner (curved part) at high speed, but also the straight (straight line part) that follows the corner has a fast corner escape speed, so the initial speed is fast. be able to. That is, if the lateral grip force can be increased, the lap time can be shortened in competitions and races.

  During cornering, it is required to grip the tire in the lateral (width) direction. In order to make a two-wheeled vehicle turn faster, it is necessary to tilt the vehicle body to balance with the centrifugal force that increases with the turning speed, and if the tire cannot grip the road surface to resist the centrifugal force. Don't be. In other words, if the grip force of the tire when the vehicle body is greatly tilted is insufficient, the vehicle cannot turn quickly, so the influence of the tire grip force on the turning performance is very large.

Here, in order to further improve the grip force of the tire during turning, a detailed study is conducted, and in particular, the grip force where the bank angle (camber angle) at which the body of a two-wheeled vehicle falls most is around 45 to 50 degrees is concentrated. It was considered to improve it. This is because, for example, in a race, the turning speed is very important, and if the turning speed is high, the speed of the straight next to the corner is also increased, and as a result, the lap time is improved. Further, even on general roads, increasing the grip force during turning can contribute to the improvement of safety.
In a tire for a two-wheeled vehicle, when the vehicle is turned with the vehicle body greatly tilted, a shoulder portion on one side of the tread of the tire is grounded to generate a grip force. The tire ground contact shape at this time will be considered.

  FIG. 12 is an explanatory diagram showing tread deformation in a cross section in the tire width direction when the two-wheeled vehicle turns. As shown in FIG. 12, when a two-wheeled vehicle turns a vehicle body, that is, turns at a camber angle (CA) of 45 to 55 degrees, the full width of the tread 2 of the tire 1 (tread). Approximately ¼ of the width is in contact with the road surface R. The substantially 1/4 area that is in contact with the ground is divided into three equal parts, and the areas A, B, and C are defined from the end of the tread 2. Here, the deformation of the tread 2 in a cross section along the tread width direction of the tire 1 is considered. This is because a lateral force is generated in the tire 1 by the deformation of the tread 2, and the deformation of the tread 2 in the lateral direction generates a camber thrust (lateral force).

FIG. 12 shows a grounding cross section of the tire 1 when turning at a CA of 50 degrees and a grounding portion shape corresponding to the grounding cross section, and the grounding portion of the tire 1 has an oval shape in which a part of the ellipse is missing. It may be a shape a or a half-moon shape b.
Described below is the deformation in the tread width direction of the region B when the grounding portion has an elliptical shape a. A point in contact with the surface of the tread 2 in the region B, that is, the road surface R is defined as Q, and a point at the deepest portion of the tread 2 inside the Q point is defined as a P point. FIG. 12 shows the trajectory of the P and Q points at the time of ground rolling. The P point is a point where the tread 2 is in contact with the belt (frame member) 3 of the tire 1 and the tire 1 is attached with CA. Draws a bow-like curve because it tilts and rolls. On the other hand, the point Q is fixed to the road surface R when the surface (tread surface) 2a of the tread 2 contacts the road surface R, and moves linearly in the direction of the road surface R, that is, the traveling direction of the tire 1.

  Due to this difference in movement, the tread 2 is subjected to lateral shearing, but is just in the relationship between a bow and a string, and is subjected to maximum lateral shearing directly under the load. Due to the amount of lateral shear, the tread 2 is subjected to lateral deformation (see FIG. 12), and the tread 2 is sheared laterally, thereby generating lateral force (camber thrust). Due to this mechanism of lateral force generation, the longer the ground contact length (the length of the tire equator in the circumferential direction of the ground contact shape), the wider the difference between the trajectories of point P and point Q, and the tread 2 is greatly sheared. The When the contact length is short, the shear amount of the tread 2 (the shear in the tire width direction which is the lateral direction) is small.

  When the ground contact portion has an elliptical shape a, the region B receives the largest shear, the region A has the largest shear, and the region C has the less shear. When the ground contact portion has a half-moon shape b, the region B and the region A are subjected to large shear, and the region C has little shear. However, this is greatly related to the CA value, and in the case of CA 45 degrees, the ground contact area that was the area C at the time of CA 50 degrees is shifted to the areas A and B in order to make a ground contact on the tire equator side. In the case of, the grounding area which was the area A at CA 50 degrees is shifted toward the areas B and C.

That is, in the turning traveling at a large CA of 45 degrees to 55 degrees CA, the lateral force is greatly earned in the areas A and C with the area B as the center.
On the other hand, when the inclination angle (bank angle, CA) of the two-wheeled vehicle is observed, the two-wheeled vehicle does not fall down until the angle becomes 45 ° to 55 ° C or more, and the region A is the road surface only when the two-wheeled vehicle is inclined at the maximum angle. This is a region that is in contact with R, and region B is also a region that is used mainly when the motorcycle is inclined significantly. That is, the region A is a region where the frequency of use increases only when the two-wheeled vehicle is greatly inclined, that is, when the lateral force is the greatest.

  In this area A, it is important to increase the grip force. However, since it is an area that becomes severe against wear and heat generation, the frequency of use is low, but the state with the most CA, that is, the input is This is a region that is used in the largest state and is a region where wear and heat generation are locally increased because contribution in other regions is reduced. Furthermore, since there is no adjacent rubber portion that resists deformation because of the tread end, deformation tends to be excessive and tends to promote wear and heat generation.

As described above, each region is summarized as follows.
Area A: Used only at the maximum CA (45 ° to 55 °), and particularly receives lateral input and greatly contributes to the generation of lateral grip force at the maximum CA (particularly, the ground contact portion has a half-moon shape b) In the case of), but susceptible to wear and heat generation.
Region B: Used mainly at the maximum CA (45 ° to 55 °) and greatly contributes to the generation of the lateral grip force at the maximum CA (particularly, when the ground contact portion has an elliptical shape a). It is grounded at the time of maximum CA and at CA 40 degrees, and is used more frequently than area A.

Area C: Used when the maximum CA (45 degrees to 55 degrees) is used, and also used in the process of reaching the maximum CA (CA: 30 degrees to 45 degrees), clearly compared to the areas A and B The frequency of use is high. Further, when CA is 45 degrees, the ground contact length becomes longer at the center of the ground contact shape, so that the lateral shear also increases.
In addition, a tire for a two-wheeled vehicle has a further characteristic point due to the characteristics of the mechanism of the lateral force generation. The difference between the trajectories of point P and point Q shown in FIG. 12 is the lateral deformation amount of the tread 2, and this lateral deformation amount (displacement) is constant. That is, since the locus of the point P and the point Q is determined by the geometric structure of the tire 1, the maximum amount of lateral shear is constant. In a normal tire, the amount of lateral shear in the region B (see FIG. 12) at the time of large CA is about 7 mm. Therefore, the amount of lateral shear is a constant about 7 mm regardless of whether the rubber of the tread 2 is hard or soft.

Therefore, if the rubber of the tread 2 is soft, the displacement is constant, so that less force is required to deform the tread 2, so that the generated lateral force is small. Conversely, if the rubber of the tread 2 is hard, the tread 2 is constant. Since a large force is required for lateral deformation by the amount, the generated lateral force becomes large. That is, the lateral force largely depends on the rigidity of the tread 2 (such as the elastic modulus and hardness of the tread rubber).
However, in the actual running state, when the tread 2 is formed of a hard rubber, it is difficult to bite into the fine irregularities of the road surface R, so the friction coefficient becomes small and it becomes slippery. The surface of the tread 2 slips, and the amount of displacement decreases and no lateral force is generated by sliding.

  FIG. 13 is an explanatory diagram showing tread deformation in a cross section in the tire circumferential direction when the two-wheeled vehicle turns. As shown in FIG. 13, when the tire 1 turns at a CA of 50 degrees, the deformation of the contact shape in the tire circumferential direction of the tread 2 is different between the region A and the region C. This is because the speed of the arranged belt 3 is different between the region C near the tire center and the region A near the tread edge. The tire 1 of a two-wheeled vehicle has a large roundness in the cross section in the tire width direction.

  For this reason, the region C is larger in the region A and the region C as the belt radius, which is the distance from the tire rotation axis to the belt 3. The speed of the arranged belt 3, that is, the belt speed from the time when the tread 2 contacts the road surface R to the time when the tire 1 rotates and the tread 2 moves away from the road surface R is higher in the region C. This is because the belt radius is obtained by multiplying the belt radius by the tire rotational angular velocity, and the rotational speed of the tire 1 is the same in both the region A and the region C.

Due to the speed difference in the belt circumferential direction, the tread 2 is in the driving state in the region C near the tire center, and the braking state is in the region A near the tire tread edge. Driving means that when the tire 1 is cut along the tire equatorial plane E, the inner surface of the tread (the surface in contact with the skeleton member inside the tire) is sheared rearward in the tire traveling direction and is in contact with the road surface R. This is a shearing state in which the tread surface 2a is deformed forward in the tire traveling direction, and is exactly the deformation that occurs when a driving force is applied to the tire.
On the other hand, the braking state is the reverse of the driving state, and the deformation of the tread 2 is sheared forward in the tire (belt 3), and the tread surface 2a that is in contact with the road surface R is deformed rearward. It is in a sheared state and is the movement of the tire 1 during braking (braking).

The deformation of the tread 2 in the tire circumferential direction occurs only when the tire 1 rolls in an idle state without receiving driving force or braking force. Then, due to the shear deformation in the tire circumferential direction, the tread 2 becomes slippery with respect to the road surface R in the regions A and C, and wear progresses. Such excessive deformation during turning is not likely to cause uneven wear on the shoulder portion of the tread 2 of the tire 1, so it is better not to have such deformation.
An object of the present invention is for a two-wheeled vehicle capable of improving a lateral grip force during turning of the two-wheeled vehicle and maintaining excellent lateral wear resistance as well as a grip force capable of maintaining the lateral grip force even during wear. It is to provide a pneumatic tire.

  In order to achieve the above object, a pneumatic tire for a two-wheeled vehicle according to the present invention is for a two-wheeled vehicle in which a pair of sidewalls are disposed radially outward of a pair of bead portions and a tread is disposed between the sidewalls. In the pneumatic tire, dissimilar rubber having a surface exposed to the tread surface is disposed in each tread shoulder portion adjacent to each sidewall of the tread, and the dissimilar rubber extends along the tread surface in the tire width direction. The width ranges from 6% to 20% of the tread deployment width, and ranges from 5% to 25% of the tread deployment width from the end of the tread, which is the boundary with the sidewall of the tread, toward the center of the tread. And is formed of a rubber member having a lower dynamic elastic modulus than the rubber member adjacent to the tread central portion side. It is a symptom.

Moreover, in this invention, it is preferable that the thickness along the tread thickness direction of the said different rubber | gum is the range of 20% or more and 60% or less of this tread thickness.
In the present invention, the average thickness in the range of up to 10% of the tread development width from the tread end portion to the tread center portion of the tread is the tread development width from the tread end portion to the tread center portion of the tread. It is preferably thinner than the average thickness in the range of 10-25%.

Moreover, in this invention, it is preferable that the width direction center part of the said tread has a multiple layer structure laminated | stacked on the tread thickness direction.
Moreover, in this invention, it is preferable that the surface layer rubber located in the tread surface side which comprises the said multilayer structure is contacting the said different rubber | gum.
Moreover, in this invention, it is preferable that the inner layer rubber positioned on the inner side of the tread constituting the multi-layer structure reaches a range where the different rubber of the tread shoulder portion overlaps.

Moreover, in this invention, it is preferable that the said inner layer rubber is contacting the said different rubber | gum.
In the present invention, it is preferable that at least a part of the wall surface of the tread end portion is reinforced with a hard rubber having a width along the tread width direction of 6 mm or less.
In the present invention, it is preferable that at least a part of the tread is formed by spirally winding a long rubber strip having a narrow width in the tire circumferential direction.
Moreover, in this invention, it is preferable to have the reinforcement belt which consists of a code | cord arrange | positioned in the tire radial direction inner side of the said tread at an angle of 0-5 degree | times with respect to a tire equator.

In the present invention, it is preferable that a protective belt having a width wider than that of the reinforcing belt is disposed on the outer side in the tire radial direction of the reinforcing belt at an angle of not less than 80 degrees and not more than 90 degrees with respect to the tire equator.
In the present invention, it is preferable that a buffer rubber is disposed at least at a part between the reinforcing belt and the protective belt.
In the present invention, it is preferable that the reinforcing belt has a width along the tread width direction in a range of 60% or more and 90% or less of the tread width.

  According to the present invention, the different types of rubber whose surfaces are exposed on the tread surface are disposed on the respective tread shoulder portions adjacent to the respective sidewalls of the tread, and the different types of rubber have a width along the tread surface in the tire width direction. The tread width is 6% or more and 20% or less, and the tread edge width is 5% or more and 25% or less from the tread edge to the center of the tread. The rubber member is formed of a rubber member having a lower dynamic elastic modulus than the rubber member adjacent to the tread central portion side.

  For this reason, it is possible to improve the lateral grip force during turning of the two-wheeled vehicle and to provide excellent wear resistance together with the grip force capable of maintaining the lateral grip force even during wear.

The best mode for carrying out the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is an explanatory sectional view taken along the tire width direction of a pneumatic tire for a two-wheeled vehicle according to a first embodiment of the present invention. As shown in FIG. 1, a pneumatic tire 10 for a two-wheeled vehicle includes a tread 11 along the tire circumferential direction, and a pair of sidewalls 12 that continuously form the tire side surfaces. A bead portion 13 is provided on the inner circumferential side of each sidewall 12 in the tire radial direction, and a bead core 14 is disposed in each of the pair of left and right bead portions 13.

That is, a pair of sidewalls 12 is disposed on the radially outer side of the pair of bead portions 13, and the tread 11 is disposed between the sidewalls 12.
Between the pair of left and right bead cores 14, a carcass 15 made of a single ply (body ply) straddling the pair of bead cores 14 in a toroidal shape is disposed. A reinforcing belt (spiral belt) 16 is provided on the outer side of the carcass 15 in the tire radial direction, and an inclined belt 17b is provided on the outer side of the reinforcing belt 16 in the tire radial direction. Further, a wide protective belt 17a is provided on the outer side in the tire radial direction of the inclined belt 17b, and a tread rubber 18 forming the tread 11 is provided on the outer side in the tire radial direction of the protective belt 17a. Is arranged.

That is, the pneumatic tire 10 for a two-wheeled vehicle has a laminated structure in which a reinforcing belt 16, an inclined belt 17b, a wide protective belt 17a, and a tread rubber 18 are stacked on a carcass 15, and the cord of the carcass 15 is In addition, the tire has a radial structure in which the angle with respect to the tire equator is 90 degrees and is radially arranged when viewed from the tire center.
For example, the carcass 15 is formed by twisting a cord made of nylon to have a diameter of about 0.6 mm, and driving the carcass 15 into a sheet shape with unvulcanized rubber. It is formed as a member. The carcass 15 is fixed at the bead portion 13 by winding the ply around the bead core 14.

The reinforcing belt 16 is disposed as a belt reinforcing layer at an angle of 0 to 5 degrees with respect to the tire equator. A belt member in which one or a plurality of cords are covered with a rubber member is used in the tire manufacturing process. It is formed by winding substantially parallel to the tire equator so as to be spirally wound around the tread portion. The belt member of the reinforcing belt 16 is formed by, for example, driving a cord made of twisted aromatic polyamide fibers (Kevlar: trade name of DuPont) to a diameter of about 0.7 mm at a driving number of 50/50 mm. .
That is, the reinforcing belt 16 is a belt that includes therein a cord disposed at an angle of 0 to 5 degrees with respect to the tire equator direction, and a continuous body in which one or a plurality of cords are covered with unvulcanized rubber. It is formed by continuously spirally winding along the tire circumferential direction.

  In such a belt, since the cord is along the tire circumferential direction, the tire does not easily expand due to centrifugal force, and is particularly excellent in steering stability performance during high-speed running. Therefore, although it has come to be widely used in recent high-performance tires, it is effective in obtaining steering stability during high-speed driving, whereas it is turning at a CA of 45 to 55 degrees with the vehicle body greatly tilted. However, since the speed is low, the effect of being difficult to centrifugally expand is reduced, and the lateral grip is not much different from a conventional tire without a reinforcing belt. Therefore, it is preferable to apply the present invention to such a high performance tire because the lateral grip at the time of large CA is increased and the performance balance as a high performance tire is improved.

The reinforcing belt 16 may be formed of a steel member. For example, a steel cord in which three steel single wires having a diameter of 0.21 mm are twisted (1 × 3 × 0.21) is driven by 30 / It may be driven by 50 mm and wound into a spiral shape.
The inclined belt 17b is formed by, for example, forming a cord made of twisted aromatic polyamide fiber to a diameter of 0.7 mm and driving it at a driving number of 30/50 mm, and two of them, an angle of about 50 degrees with respect to the tire equator It is arranged crossing at.

  The protective belt 17a is formed by, for example, driving a cord made of twisted aromatic polyamide fiber to a diameter of 0.6 mm at a driving number of 50/50 mm. The protection belt 17 a protects the reinforcement belt 16, is disposed at an angle of 80 degrees or more and 90 degrees or less with respect to the tire equator, and is formed wider than the belt width of the reinforcement belt 16. Since the reinforcing belt 16 is difficult to extend in the tire circumferential direction, the reinforcing belt 16 is disposed to prevent the tire from being centrifugally expanded. By providing the reinforcing belt, the belt rigidity can be kept relatively high, so that there is also a tire in which the belt portion is configured only from the reinforcing belt. Further, since the rigidity of the belt increases when the reinforcing belt is used, the protective belt fitted to the reinforcing belt is mostly at an angle of 45 to 80 degrees with respect to the tire equator, and the reinforcing belt almost receives the internal pressure of the tire.

Therefore, if the reinforcing belt is damaged, it may lead to a tire burst. For example, if the tread is worn and thinned and you stepped on a protrusion at high speed, or if you continue to use a worn tire and the reinforcement belt is exposed, the reinforcement belt may break It cannot be said that there is no. Therefore, a protective belt 17a having a cord along the tire width direction is disposed so as to protect the reinforcing belt 16.
Here, the structure including the reinforcing belt 16 has been described. However, a structure without the reinforcing belt 16 may be used. In this case, for example, two inclined belts 17b are disposed with an inclination of about 30 degrees with respect to the tire equator. . In addition, a structure including only the reinforcing belt 16 without the inclined belt 17b may be provided, and instead of the inclined belt 17b, one protective belt 17a is disposed at an angle of about 90 degrees with respect to the tire equator. May be.

The tread rubber 18 has a thickness along the tire radial direction of about 7 mm, and is adjacent to each sidewall 12 from the center in the tire width direction (tire center), on the side of each tread end 11a. Each tread shoulder portion 11b has the same thickness. At least a part of the tread rubber 18 is formed by winding a long and narrow rubber strip in a spiral manner in the tire circumferential direction.
FIG. 2 is an explanatory plan view showing a tread pattern of the pneumatic tire for a motorcycle of FIG. As shown in FIG. 2, diagonal grooves 18a having a width of 8 mm along the tire width direction and a depth of 5 mm along the tire radial direction are alternately arranged on both sides of the tire equator. Thus, a C-shaped tread pattern is formed. The proportion of the tread pattern in the entire tread is 10%.

When manufacturing a tire, conventionally, a rubber continuous body having a narrow cross section made of unvulcanized rubber is wound around the tire in the circumferential direction of the tire (see, for example, JP-A-2006-240098). Since the shoulder section is a section made of a circular arc with a large curvature along the tire width direction, if a wide tread material is manually placed by an operator as in the prior art, molding accuracy (shape accuracy) is ensured. Is difficult. Therefore, if a narrow unvulcanized rubber continuous body is automatically wound and molded using a dedicated molding machine, the shape accuracy can be increased.
The tread rubber 18 has a rubber layer made of an inner rubber 19 disposed inside the tread center portion. The inner rubber layer 19 is made of a rubber member having a Shore A hardness of 50 ° C. at 50 ° C. and an extremely low loss tangent (tan δ) as a loss coefficient. The rubber width as a tire width direction length is about 140 mm and the rubber thickness is 3 mm. Is formed.

In the pneumatic tire 10 for a two-wheeled vehicle, for example, the tread deployment width is about 240 mm, the width of the reinforcing belt 16 is about 240 mm, and the width of the inclined belt 17b arranged on the inner side in the tire radial direction is about 245 mm. The width of the protective belt 17a is about 250 mm. The tread development width refers to the width along the curved surface of the tread surface from the one side end portion to the other side end portion of the tread 11 in the cross section along the tread width direction. The tread 11 made of a curved surface having a rounded shape is displayed in correspondence with a plane whose arc length is a straight line.
And, each tread end portion 11a side that is a boundary with each sidewall 12 of the tread 11, that is, each tread shoulder portion 11b adjacent to each sidewall 12 is a rubber member adjacent to the tread center portion side. Dissimilar rubber 20 having a rectangular cross-sectional shape made of different types of rubber members is disposed with its surface exposed to the surface of tread 11.

In this way, by disposing different types of rubber 20 on the tread shoulder portion 11b, the type of rubber member is made different between the tread surface portion of the tread shoulder portion 11b and the inside of the tread, and the tread that forms the inside of the tread on the tread surface portion. A dissimilar rubber 20 softer than the rubber 18 is disposed. The dissimilar rubber 20 that is a soft rubber member is arranged on the tread surface part because the soft rubber member bites into the fine irregularities of aggregate such as asphalt that is a paving member of the road surface R, and the friction coefficient becomes high and the tire grip Because it will improve.
On the other hand, as described above, the lateral displacement amount of the tread shoulder portion 11b of the motorcycle tire is determined by the geometric structure, and if all of the tread shoulder portion 11b is softened, the shear rigidity of the tread. Decreases, and a large lateral force cannot be generated. Therefore, only the tread surface portion is softened.

  The hardness of the tread rubber 18 is defined by a dynamic elastic modulus (E ′) or a Shore A hardness. The dynamic elastic modulus can be measured, for example, by applying a sine wave vibration having a frequency of 15 Hz and a strain of 5% to a rubber sample and measuring the reaction force at that time. In the present invention, measurement was performed at a temperature of 100 ° C., a frequency of 15 Hz, and a strain of 5% using a viscoelasticity measuring apparatus (manufactured by Rheometrics). In particular, in the case of motorcycle tires, the tread temperature of the tread shoulder portion 11b may exceed 100 ° C., and therefore, it is measured at a temperature higher than 100 ° C. depending on the purpose. The measured value is the dynamic elastic modulus. In the case of a racing tire, it is desirable to use a dynamic elastic modulus measured at a temperature of 100 ° C. or higher.

Moreover, you may use Shore A hardness instead of a dynamic elastic modulus. The Shore A hardness can be measured using a commercially available hardness meter. For example, after tread rubber is cut out and stored in a high temperature chamber kept at 50 ° C. for 30 minutes to bring the rubber temperature to 50 ° C., the hardness meter is used. Measure hardness. Usually, a material having a high hardness also has a high dynamic elastic modulus.
The different rubber 20 has a width (W) along the tread surface in the tire width direction within a range of 6% or more and 20% or less of the tread development width with the tread development width as a reference (100). Is located in a range of 5% or more (L1) or 25% or less (L2) of the tread deployment width (see FIG. 1) from the tread end 11a, which is the boundary between the tread and the tread center.

  This is based on how the tread is used during a large CA. As described above, the region where the tire of a two-wheeled vehicle comes into contact with a large CA of 45 to 55 degrees is 1/4 of the tread deployment width, that is, 25% (see FIG. 12). The area B contributes to the lateral force in consideration of the use frequency, and the area B is the largest, followed by the area C and the area A. On the other hand, the region A is a region where it is particularly necessary to take measures against local wear and heat generation.

  That is, if the width along the tread width direction of the different rubber 20 is less than 5% of the tread development width with the tread end portion 11a as a base point, it is included in the region A, but soft rubber is used for wear and heat generation. I can't. In particular, distortion becomes concentrated when it becomes relatively soft as compared with the surrounding rubber member, and further promotes wear and heat generation. On the other hand, when the width exceeds 25% of the tread development width, the region is further on the tire center side than the region C, so that the region does not substantially contribute to lateral force. Further, if the width of the tread is 5% or less, at least the region B cannot be covered, so that the effect is not obtained so much. If the width of the tread is 21% or more, the tread width is 1/4 (25%). Since it deviates from the region contributing to the lateral force, the effect cost obtained is dull.

Therefore, the width along the tread width direction is defined as 6% or more and 20% or less of the tread development width. Thereby, the different rubber | gum 20 can cover the area | region B and the area | region C (refer FIG. 12).
Further, the different rubber 20 is formed of a rubber member having a low dynamic elastic modulus or a small Shore A hardness as compared with the rubber member adjacent to the tire center portion side. That is, the dissimilar rubber 20 is softer than the rubber in the portion corresponding to the region D (see FIG. 12) on the tire center portion side (here, the portion is heavily worn at the time of acceleration at CA 40 degrees or less). It is necessary.
As an example, the hardness of the dissimilar rubber 20 is set to 1.16 MPa to 7.20 MPa in the case of dynamic elastic modulus and 30 degrees to 70 degrees in the case of Shore A hardness.

Further, a rubber member made of a material harder than the different rubber 20 or a loss tangent is provided in the inside of the tread rubber 18 in which the different rubber 20 is arranged on the surface side of the tread shoulder 11b, that is, a portion located inside the different rubber 20. It is desirable to use a rubber member having a low (tan δ), and if the rubber used is the same rubber as the rubber adjacent to the tread center portion side, efficient production becomes possible.
Thus, by disposing different types of rubber 20, it is possible to increase the grip force at the tread surface portion and increase the shear deformation, and by hardening the rubber inside the tread, the lateral force (camber thrust) is increased. Can be increased.

FIG. 3 is a cross-sectional explanatory view similar to FIG. 1 for explaining the rubber thickness of the dissimilar rubber shown in FIG. As shown in FIG. 3, the soft rubber (dissimilar rubber 20) on the tread surface portion disposed on the tread shoulder portion 11b of the pneumatic tire 10 for a two-wheeled vehicle is considered to bite into the unevenness of the road surface R. The thickness in the tread depth direction (d1), which is the thickness in the tire radial direction, is in the range of 20% to 60% of the total thickness of the tread (thickness of the tread rubber 18: D) along the depth direction of the tread 11. .
Generally, the macro unevenness of the road surface R is about 1 mm to 3 mm, and a value sufficient to cover the range is set. Furthermore, some tires for competition, for example tires used for qualifying, are intended to be able to run only one lap faster. In such a tire, the thinner one is due to the balance between rigidity and grip. It is preferably 20% or more and 40% or less of the total thickness (D) of the tread.

  FIG. 4 shows a modification of the dissimilar rubber of FIG. 1, and (a) to (c) are cross-sectional explanatory views of tread shoulder portions of the modifications (No. 1) to (No. 3). As shown in FIG. 4, the dissimilar rubber 20 has a cross-sectional shape along the tire width direction of a dissimilar rubber 20a having a horizontally long rectangular shape (see (a)) or a trapezoidal dissimilar rubber 20b having a short tread surface side ((b)). Or a portion where the dissimilar rubber 20 is disposed may have an upper and lower two-layer structure and may be positioned only in the upper layer portion (see (c)).

FIG. 5 is a partial cross-sectional explanatory view showing a mounting state of hard rubber that reinforces the tread edge. As shown in FIG. 5, you may reinforce at least one part of the tread wall surface of the tread edge part 11a with the hard rubber 21 whose width along a tire width direction is 6 mm or less. Here, the hard rubber 21 is a rubber harder than the rubber forming the tread 11, and specifically, a rubber having a Shore A hardness of 60 or more and 95 or less at room temperature. When the wall surface of the tread end portion 11a is fixed with such hard rubber, the tread 11 is prevented from falling when the tread 11 is laterally deformed, and the tread end portion 11a can be prevented from rising from the road surface R.
In particular, since soft rubber (dissimilar rubber 20) is disposed on the surface of the tread shoulder portion 11b, it is more effective to reinforce the wall surface of the tread end portion 11a with such hard rubber (hard rubber 21). is there. In order to suppress the tread 11 from falling down, although depending on the hardness of the rubber, the hard rubber 21 may have a width of about 1 mm, and preferably 2 mm or more and 5 mm or less.

  FIG. 6 is a cross-sectional explanatory view similar to FIG. 1 for explaining an average rubber thickness in the pneumatic tire for a motorcycle of FIG. As shown in FIG. 6, the average thickness (d2) of the pneumatic tire 10 for a two-wheeled vehicle in a range (W2) from the tread end portion 11a of the tread rubber 18 forming the tread 11 to 10% of the tread deployment width. Is formed thinner than the average thickness (d3) in the range (W3) from the tread end portion 11a of the tread rubber 18 to 10 to 25% of the tread developed width.

That is, the thickness of the portion of the tread 11 where the soft rubber (different rubber 20) is disposed is set to be thinner than the other portions. A range (W2) of the tread development width from the tread end portion 11a (W2) corresponds to substantially the center of the portion where the dissimilar rubber 20 is disposed on the tread surface, and 10 percent of the tread development width from the tread end portion 11a. A range (W3) starting from the tread end portion 11a and ending at 25% of the tread deployed width (W3) corresponds to the remaining ground contact portion when the tire turns at 50 degrees CA (see FIG. 12).
Thus, if the site | part in which the soft rubber | gum (different rubber | gum 20) of the tread 11 is arrange | positioned thinly, tread rigidity will improve. That is, the overall thickness of the tread 11 is reduced by the softening of the rubber of the tread 11.

In addition, since the tread rigidity is substantially proportional to the tread thickness, when the tread thickness is 8 mm, about 0.5 to 1.5 mm has a sufficient effect. Further, when the entire thickness of the tread is reduced, the tread rigidity is improved, but the slip on the tire surface is increased as a whole, and the life until the end of wear (wear life) is reduced. Therefore, the part where the soft rubber is arranged is thinned.
Further, a rubber layer (buffer rubber) serving as a buffer layer may be disposed at least at a part between the protection belt 17a and the reinforcing belt 16. Thereby, abrasion of the tread of the tread shoulder portion 11b can be suppressed.

  If rubber (buffer rubber) serving as a buffer layer is provided at least partly between the protection belt 17a and the reinforcing belt 16, the buffer rubber undergoes shear deformation in the tire circumferential direction, so that driving deformation and braking deformation (see FIG. 13), the deformation of the tread 11 in the tire circumferential direction is alleviated. On the other hand, since the shock absorbing rubber has the protective belt 17a along the tire width direction on the upper surface thereof, it is difficult to be sheared and deformed in the tire width direction. Therefore, the deformation of the tread 11 is not replaced with respect to the tire width direction, and the lateral shear deformation of the tread 11 remains large even when the buffer rubber is arranged.

  That is, the shock absorbing rubber replaces only the deformation in the tire circumferential direction and reduces the deformation in the tire circumferential direction of the tread 11 to prevent uneven wear, while the deformation in the tire width direction does not replace the shoulder and deforms the tread 11 laterally. Is kept large and has the effect of keeping the lateral force (camber thrust) high. When soft rubber (dissimilar rubber 21) is arranged on the surface of the tread shoulder portion 11b as in the present invention, the soft rubber is easily worn, and thus it is very effective to provide such a buffer rubber. The protective belt 17a and the shock absorbing rubber are preferably arranged widely so as to overlap the place where the different rubber 21 is arranged at the end of the tread.

Further, the belt width along the tire width direction of the reinforcing belt 16 is set in a range of 60% or more and 90% or less of the tread width along the tire width direction of the tread 11. This means that the reinforcing belt 16 does not exist in the region A (see FIG. 13). If the reinforcing belt 16 is not present in the region A, the inclined belt 17b in the region A can extend in the tire circumferential direction.
Since the tread in the region A is in contact with the road surface R (depressed) and then undergoes braking deformation until it is separated (kicked out) from the road surface R, the tread is pulled to extend the inclined belt 17b in the tire circumferential direction (see FIG. 13). . If the inclined belt 17b can extend in the tire circumferential direction in the region where the tread 11 is in contact with the ground, braking deformation of the tread 11 can be reduced.

  That is, in the region where the inclined belt 17b is in contact with the ground, extending in the tire circumferential direction means that the belt speed is increased, and the speed difference between the inclined belt 17b in the region C and the region A is reduced, so that the tire circumferential direction of the tread 11 is reduced. This leads to suppression of excessive deformation (braking deformation). Regarding the tread 11 in the region A, the absence of the reinforcing belt 16 that does not extend in the tire circumferential direction causes the inclined belt 17b to extend in the tire circumferential direction, and the braking deformation is alleviated. As a result, slipping is reduced, and wear resistance performance is improved even when soft rubber (different rubber 21) is mounted on the tread surface.

Thus, if the width of the reinforcement belt 16 is not narrow and the reinforcement belt 16 does not exist in the region A instead of the above-described conventional structure in which the width of the reinforcement belt 16 is wound around the entire tread width, the wear resistance performance. It becomes possible to mount soft rubber (dissimilar rubber 20) on the surface of the tread shoulder portion 11b.
The width of the reinforcing belt 16 is set to 60% or more and 90% or less of the tread width because the center portion in the tire width direction of the ground shape shown in FIG. 13 is 12.5% from the tread end portion 11a. If the width of the reinforcing belt 16 is defined at the center, the width is 75%. Therefore, the width is defined with 75% as the center value.

  When the width of the reinforcing belt 16 is 90% of the tread width, a range of 5% from the tread end portion 11a is a portion where the reinforcing belt 16 is not wound. When the reinforcing belt 16 exceeds 90%, the belt in the region A is in the tire circumferential direction. And the effect of relaxing the braking deformation in the region A is reduced. Less than 60% of the tread width means that the width of the reinforcing belt 16 is narrower than the position 15% from the end of the tread, and a width wider than 15% also means the reinforcing belt 16 in the region C (see FIG. 13). Since the belt tends to extend in the tire circumferential direction due to the ground contact in the region C, the speed difference between the belts in the region A and the region C in the tire circumferential direction is not reduced.

Further, since the reinforcing belt 16 does not exist in most of the ground contact area, the tagging effect of the reinforcing belt 16 is weakened, and the steering stability performance at high speed is deteriorated. Therefore, the spiral width is preferably 60% or more and less than 90%.
Next, using the pneumatic tire 10 for motorcycles based on the above-described configuration (see FIG. 1) as a basic structure, the tires of the conventional example, the comparative example, and the example were prepared, and various evaluations were performed.

  The tire of Conventional Example 1 forms a tread with one kind of rubber having a dynamic elastic modulus of 4.0 MPa at a temperature of 50 ° C. The dynamic elastic modulus was measured at a temperature of 50 ° C., a frequency of 15 Hz, and a strain of 5% using a viscoelasticity measuring apparatus (manufactured by Rheometrics), and this was expressed as 100. Further, the tire center portion having two layers having the same configuration as that of the example 1 is used as the tire of the conventional example 2, and the tire of the conventional example 2 having the end portion 0.7 mm thinner is the tire of the conventional example 3. It was.

The pneumatic tire 10 for a two-wheeled vehicle shown in FIG. The size is 190 / 50ZR17.
In the tire of Example 1, soft rubber (different rubber 20) was disposed on the surface of the tread shoulder portion 11b. The disposition width of the dissimilar rubber 20 (width along the layer in the tire width direction on the tread surface) is 24 mm, the depth (depth along the tire radial direction) is 4 mm, and the index of dynamic elastic modulus is 70. The boundary in the depth direction between the different rubber 20 and the rubber adjacent to the tire center portion side of the different rubber 20 is positioned perpendicular to the depth direction without being inclined.

Further, the tire center portion is divided into two upper and lower layers, and the surface layer is the same as the rubber adjacent to the tire center portion side of the soft rubber disposed on the tread shoulder portion 11b and has a dynamic elastic modulus of 100. In the inner layer, rubber having an index of dynamic elastic modulus of 150 is disposed. The width of the rubber arranged in the inner layer along the tire width direction is 120 mm, and the width of the reinforcing belt 16 along the tire width direction is 240%, which is 100% of the tread deployed width.
And the following evaluation was performed about each tire of a prior art example, a comparative example, and an Example.
[CA50 degree lateral force (camber thrust) measurement]

Paste # 40 sandpaper on a steel drum with a diameter of 3m and make it look like a road surface. The tire is installed in a foil having a rim width of 6 inches and a rim diameter of 17 inches, and is filled with an internal pressure of 240 kPa.
The tire is pressed against the drum at a CA of 50 degrees, a load of 1500 N, and a slip angle (Slip Angle: SA) of 0 degrees, and is rotated at a speed of 40 km / h. The lateral force at this time was measured with a three-component force meter attached to the rotating shaft of the tire, and the lateral force (1350 N) of Conventional Example 1 was expressed as an index with the reference value (100). The lateral force was measured after 5 minutes from the start of rotation of the tire (at this time, the tire was sufficiently warmed and the tread shoulder portion had a tread temperature of about 50 ° C.).
[Rolling resistance test]

The rolling resistance test was performed using a rolling resistance tester at an internal pressure of 240 kPa, a load of 1500 N, SA 0 degrees, CA 0 degrees, and 80 km / h, and the measurement results were evaluated. The evaluation was expressed as an index with the rolling resistance of Conventional Example 1 as the reference value (100). The smaller the index, the less the resistance and the more fuel efficient.
[Evaluation in the test course]

A comprehensive driving stability test was carried out by running an actual vehicle by a skilled rider on the test course. Since the prepared tire was for the rear, a conventional tire was used for the front. The two-wheeled vehicle used was a sports-type vehicle with a displacement of 1000 cc, and was evaluated comprehensively with a test rider feeling of 10 points, centering on the steering stability (cornering performance) when the car body was greatly tilted.
For the turning evaluation, there are 6 corners that can be defeated to 50 degrees CA at a speed of around 50km / h, and a circuit with a lot of left turns is used as a test course. The lap time for one lap was 15 laps with about 60 seconds, giving a comprehensive sensory score.
[Evaluation of wear amount]

Before the actual vehicle test described above, the weight of the tire was measured, and after 15 laps of the test course, deposits such as rubber bags and pebbles adhered to the tire were removed, and the weight of the tire was measured. The difference in weight between the new product and the travel obtained from the measurement result can be evaluated as the amount of wear. Since the special test course had many corners, wear was concentrated in the shoulder. In other words, the difference in weight between when new and after traveling can be considered as the amount of wear on the shoulder due to traveling. The amount of wear of the conventional tire was expressed as an index with a reference value (100), and compared with the amount of wear of other tires. The larger the value, the greater the amount of wear.
Table 1 summarizes various setting values and evaluation results of Conventional Examples 1 to 3, Comparative Examples 1 to 7, and Examples 1 to 14. In the table, “surface rubber” is soft rubber (different rubber 20) disposed on the surface of the tread shoulder portion 11b.

Discussion [Effect of width and position of soft rubber (different rubber 20) on the surface of the tread shoulder]
By comparing the results of Conventional Example 2, Comparative Examples 1 to 5, and Examples 1 to 6, the effect of the width of the soft rubber (dissimilar rubber 20) along the tire width direction and the position of the placement can be understood.
Compared to Conventional Example 2 (without soft rubber), the soft rubber with a rubber width of 15 to 50 mm placed on the tread surface has an increased lateral force (camber thrust) at the drum, and has a lateral grip force. It turns out that there is an effect to improve.
By comparing Comparative Example 1 and Example 2, it can be seen that the effect is not exhibited unless the width of the soft rubber is at least 15 mm, that is, 6% or more of the tread development width. Further, from Examples 3 and 4 and Comparative Example 3, it is understood that the effect margin is lost when the width of the soft rubber is 50 mm or more, that is, 21% or more of the tread development width. This tendency also appears in the steering stability performance score on the test course, and it can be seen that if the width of the soft rubber is 46 mm or more, the score is the same level with 10 points.

On the other hand, when the results of Comparative Examples 2 and 3 are seen, when the tire is arranged on the tire equator side from 25% of the tread deployed width from the tread end portion 11a, the rolling resistance during straight running tends to increase. Is seen. Further, from Comparative Examples 4 and 5 and Examples 5 and 6, when the placement of the soft rubber is within a range of less than 5% of the tread developed width from the tread end portion 11a, the wear at the tread end portion 11a is advanced. .
From the above, for the tire in this example, it was found that the width of soft rubber (dissimilar rubber 20) is about 15 mm to 48 mm. Therefore, in the present invention, the width of the soft rubber is set to the tread development width. Of 6% to 20%. Furthermore, the arrangement of the soft rubber was set in a range from 5% to 25% of the tread development width with the tread end portion 11a as a base point.
[Effect of thickness of soft rubber (different rubber 20) on the tread shoulder surface]

  From the comparison of Conventional Example 2, Comparative Examples 6 and 7, and Examples 1 and 7 to 9, the effect of the thickness of the soft rubber (different rubber 20) can be seen. The soft rubber whose thickness along the tire radial direction is 1.0 mm, 1.5 mm, 2.5 mm, 3.0 mm, 4.0 mm, 4.5 mm, the lateral force index on the drum is higher than that of Conventional Example 2. In addition, the driving stability performance score on the test course is also high. However, the soft rubber having a thickness of 1.0 mm and 4.5 mm has a small effect margin, and the improvement margin is not sufficient in terms of the handling stability performance score on the test course. On the other hand, the soft rubber having a thickness of 1.5 mm or more and 4.0 mm or less has a large improvement allowance.

Therefore, the thickness of the soft rubber is set in the range of 20% to 60% of the thickness along the tire radial direction of the entire tread. Furthermore, it can be seen from Examples 7 and 8 that the thickness is preferably in the range of 20% to 40% of the total thickness of the tread. As in Comparative Example 6, when the thickness of the soft rubber is 4.5 mm or more, the tread rigidity of the tread end portion 11a is reduced and the rubber is soft and easily bites into the road surface R. Therefore, even if the friction coefficient increases, the tread This is because the lateral shear rigidity of 11 is lowered and it becomes difficult to produce a lateral force.
Therefore, it can be confirmed that it is more effective to dispose soft rubber (different rubber 20) only on the surface of the tread shoulder portion 11b as in the present invention.
[Effect of thinning the tread edge]

  In Example 10 and Conventional Example 3, the average thickness of the tread rubber in the region of 10% of the tread development width from the tread end portion 11a toward the tread center portion is the tread development width from the tread end portion 11a toward the tread center portion. The tire is 0.7 mm thinner than the average thickness of the tread rubber in the region of 10% to 25%. The average thickness of the tread rubber in the region of 10% to 25% of the tread developed width from the tread end portion 11a toward the tread central portion is 7 mm and uniform. In the range of 10% of the tread development width, the thickness of the tread rubber gradually decreases toward the end of the tread.

Further, in Example 1 and Conventional Example 2, the depth (tread gauge) along the tire radial direction of the tread 11 is 7 mm, and is uniform up to the tread end portion 11a. That is, the difference between Examples 1 and 10 and Conventional Examples 2 and 3 is the difference in the average thickness of the tread rubber in the region of 10% from the tread end portion 11a toward the tread center portion. From the comparison between Example 1 and Example 10 and the comparison between Conventional Example 2 and Conventional Example 3, the effect of thinning the tread end 11a side can be seen.
From a comparison between Example 1 and Example 10, Example 10 in which the tread end portion 11a side is thin improves the lateral force of the drum and has a high score for the steering stability performance of the test course. In the conventional example 3, the lateral force of the drum is improved compared to the conventional example 2, but the improvement margin in the example 10 is larger than that in the conventional example, and by using soft rubber for the tread shoulder portion 11b. This indicates that a synergistic effect was obtained. In addition, in Conventional Example 3, the amount of wear after traveling is large.

This is because the rubber of the tread shoulder portion 11b is not softened and only the thickness of the tread is reduced, so that the tread rigidity of the tread end portion 11a is improved as compared with other portions, and tread deformation is reduced. This is because the surface becomes slippery with respect to the road surface R. The tread of the tread end portion 11a slips and the wear of the tread end portion 11a proceeds.
On the other hand, in Example 10 in which the soft rubber is arranged on the tread surface, the rubber on the tread surface is soft and the tread deformation is large. Therefore, by reducing the thickness of the tread, the rigidity balance with other parts becomes appropriate. . Therefore, the degree of progress of wear on the tread is less than that in Example 1 before the thickness of the tread is reduced. In this way, by adjusting the tread thickness and combining the configuration where soft rubber is placed and the rubber on the tread surface is softened, steering stability is improved and the life until the end of wear (wear life) is maintained. It becomes possible.
[Effect of two-layer tire center]

The comparison between Conventional Example 1 and Conventional Example 2 and the comparison between Example 11 and Example 1 are both comparisons when the tire center portion has a two-layer structure and when it does not have a two-layer structure. Here, as in the conventional example, when no soft rubber (dissimilar rubber 20) is disposed on the tread shoulder portion 11b, there is no difference in the lateral force index on the drum even if the tire center portion is not double-layered. There wasn't.
However, as in the present invention, when the tread shoulder portion 11b is formed in two layers to generate a large lateral force, the lateral force is further increased when the tire center portion is formed in two layers. I understand. This is because the lateral deformation of the tire has increased due to the increased lateral force of the tire, and the rigidity of the tire center has increased by hardening the rubber inside the tire center. It is.

In a state where the tire is grounded at 50 degrees CA (see FIG. 13), the tire center portion is not in contact with the road surface R and is located immediately next to the ground surface. At this time, the tire center portion plays the same role as the sidewall of the tire. If this portion is hardened, the rigidity in the tire lateral direction is increased. In the case of a tire for a two-wheeled vehicle, the tire center portion is a tread portion that contacts the road surface R, but also serves as a tire side portion when turning at a CA of 50 degrees.
When a soft rubber (dissimilar rubber 20) is disposed on the tread shoulder portion 11b as in the present invention and the lateral force during tire turning is increased, the tire deformation increases, so the tire center portion is reinforced. This improves the handling stability. That is, since the tire center portion has a two-layer structure and rubber (hard rubber) having a high dynamic elastic modulus is arranged inside, the lateral grip is also improved.

Thus, the two-layered tire center portion not only reduces the rolling resistance during straight running but also saves fuel consumption, but also shows the surface of the tread shoulder portion 11b as shown in this embodiment. When combined with the arrangement of soft rubber, the lateral grip can be further improved.
[About the softness of rubber]
Next, a tire in which the dynamic elastic modulus of the surface rubber (dissimilar rubber 20) to be arranged was changed using the tire structure in Example 1, and the influence of the dynamic elastic modulus was examined.

From comparison between Examples 1 and 12 to 14 and Conventional Example 2, the following can be said about the dynamic elastic modulus of rubber.
When the dynamic elastic modulus index of rubber is 90, the lateral force improving effect is small. This is because the effect is reduced because the difference in hardness is small. Further, when the dynamic elastic modulus index of the rubber is 20, the lateral force improving effect is similarly small. This is because the rubber becomes softer and the bite into the road surface R increases and the friction coefficient is improved, but the rubber is too soft and the tread lateral shear rigidity is lowered to offset the improvement of the friction coefficient. . Also, the wear performance is greatly deteriorated as compared with Comparative Example 1.

From the tendency of this example, when the dynamic elastic modulus index of the rubber is 70 and 40, a preferable result is obtained. Therefore, it is possible to judge that the dynamic elastic modulus index of the rubber is 30 to 80. it can.
(Second Embodiment)
FIG. 7 is a cross-sectional explanatory view along the tire width direction of a pneumatic tire for a two-wheeled vehicle according to a second embodiment of the present invention. As shown in FIG. 7, the pneumatic tire 30 for a two-wheeled vehicle has a carcass 31 composed of a plurality (for example, two) plies (body plies).

The ply is formed by driving a cord made of twisted aromatic polyamide fibers (Kevlar: DuPont's trade name) to a diameter of about 0.6 mm so that the number of shots at the tire center is 40/50 mm. ing. The two plies are arranged so as to intersect each other at the tire center portion so as to have an angle of 40 degrees with respect to the tire equator. In the bead portion 13, two plies are gathered together from both sides with bead wires 32. The carcass 31 is fixed by being sandwiched.
A reinforcing belt (spiral belt) 16 is formed on the outer side of the carcass 31 in the tire radial direction, a protective belt 17 is formed on the outer side of the reinforcing belt 16 in the tire radial direction, and a tread 11 is formed on the outer side of the protective belt 17 in the tire radial direction. Rubbers 18 are respectively disposed.

The reinforcing belt 16 is disposed as a belt reinforcing layer at an angle of 0 to 5 degrees with respect to the tire equator. A belt member in which one or a plurality of cords are covered with a rubber member is used in the tire manufacturing process. It is formed by winding substantially parallel to the tire equator so as to be spirally wound around the tread portion. Here, seven steel single wires having a diameter of 0.12 mm were twisted to form one steel cord, and this was formed by spirally winding the tread so that the number of driven wires was 50/50 mm.
The protective belt 17 is formed by, for example, forming a cord made of twisted aromatic polyamide fiber to a diameter of 0.6 mm by driving the cord at a driving number of 50/50 mm, and an angle of about 90 degrees with respect to the tire equator. It is arranged crossing at.

The tread deployment width is about 240 mm, the reinforcing belt 16 is about 235 mm, and the protective belt 17 is about 240 mm.
The tread 11 has the same thickness of 8 mm from the tread center portion to the tread shoulder portion. Inside the tread center portion, the width along the tire width direction is 120 mm, the Shore A hardness is 50, and the loss tangent ( A rubber (inner layer rubber) having a very low tan δ is disposed with a thickness of 4 mm, and a rubber (surface rubber) having a width of 90 mm and a Shore A hardness of 45 at 120 ° C. is disposed thereon.
That is, the pneumatic tire 30 for a two-wheeled vehicle has a two-layer structure in which the inner layer rubber 19 and the surface layer rubber 33 are laminated at the center in the tire width direction (tire center), that is, the center in the width direction (tread center) of the tread 11. have.

Heat generation in the tread 11 can be suppressed by making the tread center part a two-layer structure in which the inner layer rubber 19 and the surface layer rubber 33 are laminated.
Here, the tread center portion is a range of approximately 25% of the center portion of the tread width direction and the entire tread width. When the two-wheeled vehicle is in an upright state, the contact width between the tire tread 11 and the road surface R is the tread width. This is due to approximately 25% of the entire area. Note that the two-layer structure may not be the entire range of approximately 25% of the entire tread width, and is effective if it is at least a large part, specifically, a range of 15% or more of the entire tread width. Is obtained.

  As a two-layer structure, if hard rubber (inner layer rubber 19) is placed inside the tread and soft rubber (surface rubber 33) is placed on the tread surface, the rubber on the tread surface gains grip and the internal rubber generates heat. Suppress. Further, if a rubber having a low loss tangent (tan δ) is used for the inner layer rubber 19, heat generation of the rubber can be further suppressed. In a racing tire, the speed may exceed 300 km / h during straight running. In such a case, the tread is repeatedly deformed at a high frequency by high speed running and generates heat.

The heat generation causes a blowing phenomenon in which the added oil component inside the tread rubber is vaporized and bubbles are generated, and a part of the tread rubber may be chipped and scattered from the bubbles. Therefore, in such competition tires with severe use conditions, rubber with a very low loss tangent (tan δ) that does not easily generate heat is used inside the tread, while rubber with high grip strength is used on the tread surface. Good.
In this way, by using the two-layer structure of the inner layer rubber 19 and the surface layer rubber 33, it is possible to improve not only a large CA of 45 to 55 degrees CA but also a driving characteristic and a braking characteristic when traveling straight.

The inner layer rubber 19 and the surface layer rubber 33 used in the tread center part which is the center part in the width direction of the tread 11 are arranged with a space for interposing the tread rubber 18 between the different kinds of rubbers 21 (see FIG. 7) is not limited to this arrangement example.
8 to 10 are cross-sectional explanatory views similar to FIG. 7, showing other examples (No. 1 to No. 3) of the arrangement state of the inner layer rubber and the surface layer rubber.

As shown in FIG. 8, the surface rubber 33 extends in the tread width direction toward both tread end portions 11 a and is brought into contact with the tire center side end portion of the different rubber 21. As a result, the outer surface (tread surface) of the tread 11 is formed of the dissimilar rubber 21 and the surface rubber 33 over substantially the entire area excluding the tread end portions 11a side. That is, since the surface rubber 33 and the different rubber 21 are connected, the types of rubber forming the tread 11 can be reduced, which is efficient.
Further, as shown in FIG. 9, the inner layer rubber 19 is extended to both tread end portions 11a side along the tread width direction, and reaches a range overlapping with the different rubber 21 below the different rubber 21 of the tread shoulder portion 11b. Place widely.

By disposing the inner layer rubber 19 in the tread center portion so as to overlap with the dissimilar rubber 21, heat generation can be suppressed. Since hard rubber (inner layer rubber 19) is arranged inside the tread 11 and soft rubber (different rubber 21) is arranged on the surface side of the tread shoulder portion 11b, the rubber on the tread surface layer gains a grip, Suppresses fever. In addition, if rubber with a low loss tangent (tan δ) is used as the internal rubber, the heat generation of the rubber can be further suppressed, and at the same time, the hard rubber is used inside, which increases the lateral force (camber thrust). Can also be expected.
The hard rubber inside may be widely present only on one side of the tire equator, and if it is widely disposed only on the side where the traveling usage is high, the heat resistance on the side where the traveling usage is high is improved. Can prevent blow failure.

Further, as shown in FIG. 10, the inner layer rubber 19 is extended to both tread end portions 11a along the tread width direction, and is arranged in a state of being in contact with substantially the entire lower surface of the dissimilar rubber 21 of the tread shoulder portion 11b. Yes. By bringing the inner layer rubber 19 and the different rubber 21 into contact with each other, the lateral force can be effectively improved and the number of types of rubber used can be reduced, which is efficient.
FIG. 11 is a cross-sectional explanatory view similar to FIG. 7 showing another example of the arrangement of the protective belt. As shown in FIG. 11, the protection belt 17 is not limited to an arrangement (see FIG. 1) that intersects the tire equator at an angle of about 50 degrees, and the angle with respect to the tire equator is 80 degrees or more and 90 degrees or less. In addition, a wide belt having a belt width in the tread width direction wider than the reinforcing belt 16 may be disposed.

If the protective belt 17 is arranged so as to overlap with the soft rubber (dissimilar rubber 21) on the surface layer portion of the tread shoulder portion 11b, the fibers reinforced in the tread width (lateral) direction are the belt layers (the reinforcing belt 16 and the protective belt 17). The base of the tread 11 becomes stronger in the tread width (lateral) direction, and the belt layer has rigidity against the lateral shear of the tread 11, so that a high lateral force (camber thrust) can be maintained. it can.
Here, as the conventional tire 4 in the pneumatic tire 30 for a motorcycle according to the second embodiment, a structure in which rubber having a Shore A hardness of 35 at 120 ° C. is disposed on both sides of the tread center portion, that is, the motorcycle. In the pneumatic tire 30 for use (see FIG. 7), a tire having a structure using a rubber having a Shore A hardness of 35 instead of the rubber disposed on the surface of the tread shoulder portion 11b is prepared.

In contrast to the conventional tire 4, the tires of the examples according to the second embodiment all have a tire center portion having a two-layer structure (the description of the configuration is omitted in Table 2). The soft rubber (dissimilar rubber 20) of the tread shoulder portion 11b has an elastic modulus index of 70 with reference to a rubber having a Shore A hardness of 35C at 35O0C disposed on both sides of the tread center portion as a reference (100).
The dissimilar rubber 20 has a width (W) along the tire width direction of 24 mm, is disposed between 20 to 44 mm from the tread end portion toward the tread center portion, and has a depth d1 of 4 mm. It is the same. However, the depth d1 is equivalent to 50% because the tread depth (tread gauge) is 8 mm.

  Table 2 summarizes various setting values and evaluation results of Conventional Examples 4 to 9, Comparative Examples 8 to 11, and Examples 15 to 28. In the table, “surface rubber” is soft rubber (different rubber 20) disposed on the surface of the tread shoulder portion 11b.

The following evaluation was performed about these prepared tires.
Three tires were prepared, one for lateral force evaluation when new, the other for lateral force evaluation assuming wear by scraping the tread surface, and the other for actual vehicle testing. The tire according to the second embodiment was evaluated as follows assuming that it is used in competition.
[CA50 degree lateral force (camber thrust) measurement (when new)]

Paste # 40 sandpaper on a steel drum with a diameter of 3m and make it look like a road surface. The tire is incorporated in a foil having a rim width of 6 inches and a rim diameter of 17 inches, and is filled with an internal pressure of 200 kPa.
The tire is pressed against the drum at a CA of 50 degrees, a load of 1500 N, and a slip angle (Slip Angle: SA) of 0 degrees, and is rotated at a speed of 100 km / h. The lateral force (camber thrust) at this time was measured with a three-component force meter attached to the rotating shaft of the tire, and the lateral force (1900 N) of Conventional Example 3 was expressed as an index with the reference value (100).

The lateral force was measured after 5 minutes from the start of rotation of the tire (at this time, the tire was sufficiently warmed and the shoulder tread temperature was about 120 ° C.).
[Evaluation of lateral force of tires assuming wear]
Next, the tire surface of each tire was uniformly cut by 3 mm. 3 mm was uniformly cut from the center part to the shoulder part. About this, the same test as the above 3m drum was made on the road surface was done, and the tire temperature 5 minutes after rotating was measured.
[Evaluation in the test course]

  A comprehensive driving stability test was carried out by running an actual vehicle by a skilled rider on the test course. Since the prepared tire was for the rear, a conventional tire was used for the front. The two-wheeled vehicle used was a sport type with a displacement of 1000 cc and used for competition. Assuming a competition, the circuit was run and the maximum speed reached 320 km / h. The overall evaluation was based on a test rider feeling of 10 out of 10.

The test was performed for 20 laps, and the average lap time for the first and last 10 laps was calculated. Obviously, the lap time when the rider missed was excluded from the average calculation. The feeling of steering stability performance was also evaluated separately for the 10 laps in the first and second half. The layout of the test course had four corners where the car body was greatly lowered at a speed of 80 to 120 km / h. Moreover, the tire temperature immediately after running 20 laps was about 120 degreeC.
[Evaluation of wear amount]
Before the actual vehicle running test, the tire weight was measured. After 20 laps of the test course, the deposits such as rubber chips and pebbles attached to the tire are removed cleanly, the tire is removed from the rim, and the tire weight is measured.

The special test course had many corners, so intensive wear occurred at the shoulder. In other words, since the difference in weight between when new and after running can be considered as the amount of wear on the shoulder, the amount of wear on the conventional tire is used as a reference value (100), and the amount of wear on other tires is compared and expressed as an index. . In Conventional Example 3, the wear amount of the shoulder portion reached 20 mm when the circuit was turned 20 times.
Consideration for the above test results [Effect of placing rubber on the tread center]

The effect of this invention is understood by comparing the prior art example 4 and Examples 15-18. Compared to Conventional Example 4, Example 15 has an improved lateral force index when scraping a 3 mm tread when new. Also, the lap time when running on the circuit is about 1.5 seconds faster, and the effect is clear. Also, the amount of wear in Example 15 is improved over Conventional Example 4.
This is because it is known that such an engine tire has a large engine power and has a large driving force during acceleration when exiting a corner, and the tire accelerates while slipping. Therefore, when the grip force of the tire is increased, the slipping of the tire is suppressed and the amount of wear can be reduced.

Moreover, the effect of rubber | gum arrangement | positioning in a tread center part is understood by comparing Example 15 and Examples 16-18. In Examples 16-18, since the kind of tread rubber can be reduced, an increase in the lateral force index can be expected while slightly increasing in addition to the merit in manufacturing. This is considered to be an effect due to uniform deformation of the tread center portion that plays the role of the side during traveling at a large CA by connecting the same kind of rubber layer from the tread center portion. This is because when the deformation becomes uniform, the concentration of local deformation is alleviated, and the portion where the side deformation increases due to the increased grip can be absorbed as a whole.
[Effect of hard rubber]

From the comparison between Example 15 and Example 19 and Conventional Example 4 and Conventional Example 6, the effect of the hard rubber 21 that reinforces the wall surface of the tread end portion 11a can be seen. A hard rubber having a Shore A hardness of 70 ° C. at 120 ° C. was used. This is harder than any rubber that forms the tread 11.
As shown in FIG. 5, the hard rubber 21 is arranged so as to reinforce the side surface of the tread end portion 11a, and the width thereof is 4 mm at the maximum portion. Further, the height is not exposed on the tread surface, and is reinforced from a position 1 mm below the tread surface in the tread thickness direction to a position 8 mm.

By disposing the hard rubber 21 as in the nineteenth embodiment, it is possible to prevent the lateral rigidity of the tread from being lowered due to the soft rubber (different rubber 20) being disposed on the tread surface. Therefore, both the drum lateral force index and the circuit index improved.
In addition, although the case where the hard rubber 21 was used for the prior art example 4 was made into the prior art example 6, in this case, the effect of improving the lateral force is less than that of the embodiment 19 where the hard rubber 21 is applied to the embodiment 15. . This is because the conventional example 4 uses a hard rubber for the tread end portion 11a, so that the lateral shear rigidity of the tread 11 can be maintained to some extent without being reinforced by the hard rubber 21. When the soft rubber (different rubber 20) is arranged on the tread shoulder portion 11b as in the present embodiment, the effect of the hard rubber 21 is very effective.
[Effect of spiral layer]

  The effects of the reinforcing belt (spiral layer) 16 can be seen from Conventional Example 4, Conventional Example 5, Example 15, and Example 20. The reinforcing belt 16 has a demerit with respect to the lateral force at the time of large CA, which is called an edge grip, while increasing traction. Comparing Conventional Example 4 and Conventional Example 5, it can be seen that by changing to the reinforcing belt 16, the lateral force index at the time of large CA is lowered. However, the average time has improved slightly. This is because the disadvantage of cornering is compensated by traction. Furthermore, wear is greatly improved.

When this reinforcing belt 16 is used at the same time as a soft rubber (different rubber 20), a reduction in lateral force can be prevented when Example 15 and Example 20 are compared. As a result, the traction effect by the reinforcing belt 16 can be sufficiently exerted, and the average time can be significantly improved compared to the rising method in the conventional example 4 and the conventional example 5. It can be seen that the combination of soft rubber (different rubber 20) in the tread shoulder portion 11b is very effective.
[Effect of protective layer]

The purpose of the protective belt 17 (protective layer) is to protect the reinforcing belt 16 as described above. However, when Example 20 and Example 21 are compared, the lateral force index is improved. This is because the protective belt 17 which is a belt reinforcing layer is a member having rigidity in the tire width direction with respect to the tire equator, so that the lateral force at the time of large CA can be transmitted to the entire tread without loss. Thus, it is very effective to achieve an increase in lateral force at the time of large CA as a synergistic effect, not just a function as a protective layer.
[Effect of cushion rubber]

  From Examples 21 to 24, Comparative Examples 8 and 9, and Conventional Examples 7 and 8, the effect of the buffer rubber can be seen. In Examples 21 to 24, a buffer rubber serving as a buffer layer is disposed between the protection belt 17 and the reinforcement belt 16. The rubber member of the buffer rubber is of the same type as the belt coating rubber covering the belt of the protective belt 17, and the thicknesses are 0.3 mm, 1.0 mm, and 3.0 mm, respectively.

  Thus, by arranging the buffer rubber, the skeleton member can flexibly move in the tire circumferential direction while enhancing the shear rigidity in the tire width direction of the skeleton member made of the belt layer (the reinforcing belt 16 and the protective belt 17). Thus, useless shearing of the tread 11 in the tire circumferential direction can be reduced. Therefore, slipping of the tire is suppressed, wear is reduced, and grip is improved. Furthermore, it is an advantage that the amount of wear is extremely small. This is because, when a tire for competition is increased in grip, slipping is reduced and wear is suppressed.

In addition, although the buffer rubber is arrange | positioned in the prior art example 7 is the prior art example 8, compared with these cases, the effect of Examples 21-24 is large. This is because the soft rubber (dissimilar rubber 20) disposed on the surface of the tread shoulder portion 11b of the present invention enhances the grip force of the tire. This is because the shock-absorbing rubber is responsible for the deformation, so that the tire is difficult to slip and the wear suppression performance is improved. Thus, the effect can be enhanced synergistically by combining with the present invention, not simply arranging the buffer rubber. Further, it can be seen from Comparative Examples 8 and 9 that an appropriate value for the thickness of the buffer rubber is 0.3 mm to 3.0 mm.
[The effect of narrowing the width of the reinforcing belt and the effect of placing soft rubber]

By comparing the conventional examples 8 and 9 with the comparative examples 10 and 11 and the examples 25 to 28, the soft rubber (different rubber 20) is disposed on the tread shoulder portion 11b and the width of the reinforcing belt 16 is reduced. I understand the effect. Compared to Conventional Example 8, in Conventional Example 9, the width of the reinforcing belt 16 is 75%. This improved the drum lateral force by 3 points.
Compared with these, Examples 25-28 arrange | position soft rubber | gum to the tread shoulder part 11b, and make the width | variety of the reinforcement belt 16 62.5%-87.5%. This is because, by reducing the width of the reinforcing belt 16, there is an effect that the deformation of the tread in the tire circumferential direction shown in FIG. 13 is alleviated. In addition, the grip force of the tire is increased and the tire is removed from the road surface. Because it became difficult to slip.

Thus, it becomes possible to increase grip force by narrowing the width of the reinforcing belt 16 and disposing soft rubber. Moreover, by comparing with Comparative Examples 10 and 11, it can be seen that the appropriate value of the width of the reinforcing belt 16 is 210 to 150 mm, that is, about 60% or more and about 90% or less of the tread width.
As described above, the pneumatic tire for a two-wheeled vehicle according to the present invention can maintain the lateral grip force even when worn by improving the lateral grip force. In particular, when used as a racing tire, it is possible to provide a tire having excellent grip and wear resistance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional explanatory view along a tire width direction of a pneumatic tire for a motorcycle according to a first embodiment of the present invention. FIG. 2 is an explanatory plan view showing a tread pattern of the pneumatic tire for a motorcycle of FIG. 1. FIG. 2 is a cross-sectional explanatory view similar to FIG. The modification of the different type | mold rubber | gum of FIG. 1 is shown, (a)-(c) is sectional explanatory drawing in the tread shoulder part of modification (the 1)-(the 3). It is a partial cross section explanatory drawing which shows the mounting state of the hard rubber which reinforces a tread edge part. FIG. 2 is a cross-sectional explanatory view similar to FIG. 1 for explaining an average rubber thickness in the pneumatic tire for a motorcycle of FIG. 1. FIG. 6 is a cross-sectional explanatory view along the tire width direction of a pneumatic tire for a motorcycle according to a second embodiment of the present invention. FIG. 8 is a cross-sectional explanatory view similar to FIG. 7, showing another example (part 1) of the arrangement state of the inner layer rubber and the surface layer rubber. FIG. 8 is a cross-sectional explanatory view similar to FIG. 7, showing another example (part 2) of the arrangement state of the inner layer rubber and the surface layer rubber. FIG. 8 is an explanatory sectional view similar to FIG. 7, showing another example (part 3) of the arrangement state of the inner layer rubber and the surface layer rubber. FIG. 8 is a cross-sectional explanatory view similar to FIG. 7, showing another arrangement example of the protection belt. It is explanatory drawing which shows the tread deformation | transformation in the tire width direction cross section when a two-wheeled vehicle turns. It is explanatory drawing which shows the tread deformation | transformation in the tire circumferential direction cross section in the case of a two-wheeled vehicle turning.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,30 Pneumatic tire for two-wheeled motor vehicles 11 Tread 11a Tread edge part 11b Tread shoulder part 12 Side wall 13 Bead part 14 Bead core 15,31 Carcass 15a Ply 16 Reinforcement belt 17 Protection belt 18 Tread rubber 18a Diagonal groove 19 Inner layer rubber 20, 20a, 20b Different rubber 21 Hard rubber 32 Bead wire 33 Surface rubber R Road surface

Claims (13)

In a pneumatic tire for a two-wheeled vehicle in which a pair of sidewalls is disposed on the radially outer side of the pair of bead portions, and a tread is disposed between the sidewalls,
In each tread shoulder portion adjacent to each side wall of the tread, dissimilar rubber whose surface is exposed on the tread surface is disposed,
The different rubber is
The width along the tread surface in the tire width direction is in the range of 6% to 20% of the tread development width,
From the end of the tread that is a boundary with the sidewall of the tread to the center of the tread, the tread is deployed in a range of 5% or more and 25% or less.
A pneumatic tire for a two-wheeled vehicle, wherein the pneumatic tire is formed of a rubber member having a lower dynamic elastic modulus than a rubber member adjacent to the tread central portion side.   2. The pneumatic tire for a motorcycle according to claim 1, wherein a thickness along the tread thickness direction of the different rubber is in a range of 20% to 60% of the tread thickness.   The average thickness in the range of 10% of the tread development width from the tread end to the center of the tread is from 10 to 25% of the tread development width from the tread end to the tread center. The pneumatic tire for a motorcycle according to claim 1 or 2, wherein the pneumatic tire is thinner than an average thickness of the range.   The pneumatic tire for a two-wheeled vehicle according to any one of claims 1 to 3, wherein a central portion in the width direction of the tread has a multi-layer structure laminated in a thickness direction of the tread.   The pneumatic tire for a two-wheeled vehicle according to claim 4, wherein a surface layer rubber positioned on a tread surface side constituting the multi-layer structure is in contact with the different rubber.   The pneumatic tire for a two-wheeled vehicle according to claim 4 or 5, wherein the inner layer rubber positioned on the inner side of the tread constituting the multi-layer structure reaches a range where the different rubber of the tread shoulder portion overlaps the different rubber. tire.   The pneumatic tire for a motorcycle according to claim 6, wherein the inner rubber layer is in contact with the different rubber.   The pneumatic for motorcycles according to any one of claims 1 to 7, wherein at least a part of the wall surface of the tread end portion is reinforced with a hard rubber having a width along the tread width direction of 6 mm or less. tire.   9. The tread according to claim 1, wherein at least a part of the tread is formed by spirally winding a long rubber strip having a narrow width in the tire circumferential direction. Pneumatic tires for motorcycles.   10. The reinforcing belt comprising a cord arranged at an angle of 0 to 5 degrees with respect to the tire equator on the inner side in the tire radial direction of the tread, according to claim 1. Pneumatic tires for motorcycles.   11. The protective belt according to claim 10, further comprising a protective belt having a width wider than that of the reinforcing belt and disposed at an angle of 80 degrees or more and 90 degrees or less with respect to a tire equator on an outer side in a tire radial direction of the reinforcing belt. Pneumatic tire for motorcycles.   The pneumatic tire for a motorcycle according to claim 11, wherein a shock absorbing rubber is disposed at least at a part between the reinforcing belt and the protective belt.   The pneumatic tire for a two-wheeled vehicle according to any one of claims 10 to 12, wherein the reinforcing belt has a width along the tread width direction in a range of 60% to 90% of the tread width. tire.

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