JP2014141163A - Motorcycle tire for irregular ground running - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motorcycle tire for irregular ground running with improved traction performance while suppressing anti-block breakage performance.SOLUTION: There is provided a motorcycle tire having a tread portion 2 for irregular ground running. The tread portion 2 includes a crown area 20 and middle shoulder areas 30 at both sides of the crown area. In the crown area 20, a plurality of crown blocks 21 is provided insulating with each other in a tire circumferential direction, and a shoulder block 32 and a middle block 31 are provided in the middle shoulder area 30. The land-sea ratios Ls 1(%) and Ls 2(%) of the crown area 20 and middle shoulder area 30 satisfy relationships of (1): 10<Ls 1<25 and (2): Ls 1+3<Ls 2<Ls 1+10.

Description

  The present invention relates to a motorcycle tire for running on rough terrain, in which traction performance is improved while suppressing block chipping.

  For example, a motorcycle tire for running on rough terrain used for a motocross or the like includes a plurality of blocks in a tread portion. In such a tire, the block bites into rough terrain such as sand or muddy ground, and obtains traction and turning force.

  For example, Patent Document 1 below proposes a motorcycle tire for running on rough terrain in which a small groove extending in the tire circumferential direction is provided on a side wall of the block to improve traction performance on rough terrain. However, even with such a tire, the improvement in traction performance is not sufficient, and further improvement has been demanded.

JP 2007-182096 A

  The inventors have made extensive studies on improving traction performance. As shown in FIG. 8, when the tire a rotates in the direction R on the hard rough road surface G, the driving force generated by the block b is mainly between the tread c of the block b and the rough road surface G. It can be divided into a frictional force generated between them and a reaction force (hereinafter also referred to as “scratching force”) when the edge d and the side wall e of the block a scratch the rough road surface G.

  The inventors have found that the crown block disposed in the crown region, which is the central portion when the tread development width is divided into three equal parts, mainly generates a scratching force. Further, the inventors have found that the middle block and the shoulder block arranged in the middle shoulder region on both sides of the crown region mainly generate the frictional force. The reason for this is that when running on a relatively hard uneven road surface, the crown block tends to penetrate deeply into the road surface due to the curved profile of the tread part, while the middle block and shoulder block stick into the road surface more than the crown block. It is thought that it is difficult.

  The inventors focused on the fact that driving force is generated by different mechanisms depending on the position of the block, and by improving the landsy ratio in each region, the traction performance was dramatically improved while suppressing block chipping. As a result, the present invention has been completed.

  The present invention has been devised in view of the above circumstances, and is based on improving the land sea ratio of the crown region and the land sea ratio of the middle shoulder region, while suppressing block missing. The main purpose is to provide motorcycle tires for running on rough terrain with improved performance.

Of the present invention, the invention described in claim 1 is a motorcycle tire for running on uneven terrain having a tread portion, wherein the tread portion is a center portion when the tread developed width is divided into three equal parts. A plurality of crown blocks spaced apart in the tire circumferential direction, and the middle shoulder region has a tire circumferential direction at a tread edge position. A plurality of shoulder blocks spaced apart from each other and a plurality of middle blocks spaced apart in the tire axial direction from the tread end in the tire circumferential direction. Ls1 (%) and the land / shoulder ratio Ls2 (%) of the middle shoulder region satisfy the relationship of the following expressions (1) and (2).
10 <Ls1 <25 (1)
Ls1 + 3 <Ls2 <Ls1 + 10 (2)

  According to a second aspect of the present invention, the area Ac of the tread of each crown block is greater than 1.0 and less than 2.5 times the area Am of the maximum tread of the middle block. This is a motorcycle tire for running on rough terrain.

  The invention according to claim 3 is the motorcycle tire for running on rough terrain according to claim 1 or 2, wherein the crown block includes a first crown block disposed on the tire equator.

  According to a fourth aspect of the present invention, the crown block includes a second crown block comprising a pair of block pieces divided by slits extending in the tire circumferential direction and disposed on both sides of the tire equator. The motorcycle tire for traveling on rough terrain according to any one of 1 to 3.

  In the invention according to claim 5, the tread surface of the middle block includes an inner edge extending on the tire equator side in the tire circumferential direction, and a development length between the inner edge and the boundary of the crown region is: The tire for motorcycles for rough terrain travel according to any one of claims 1 to 4, wherein the tire is 0 to 9% of the developed tread width.

  According to a sixth aspect of the present invention, the tread of the crown block and the middle block in a tire meridian cross section including a tire rotating shaft in a normal state in which a normal rim is assembled and a normal internal pressure is filled and no load is applied. The motorcycle tire for running on uneven terrain according to any one of claims 1 to 5, wherein the profile has a radius of curvature of 35 to 55% of the tread developed width.

In the invention according to claim 7, the rubber hardness Hc (degree) of the crown block, the rubber hardness Hm (degree) of the middle block, and the rubber hardness Hs (degree) of the shoulder block The motorcycle tire for traveling on rough terrain according to any one of claims 1 to 6, which satisfies the relationship.
70 <Hc <80 (3)
60 <Hm <HC-3 (4)
60 <Hs <HC-3 (5)

  The tread portion of the motorcycle tire for traveling on rough terrain according to the present invention includes a crown region which is a central portion when the tread developed width is divided into three equal parts, and middle shoulder regions on both sides thereof. In the crown region, a plurality of crown blocks are spaced apart in the tire circumferential direction. The middle shoulder region has a plurality of shoulder blocks spaced in the tire circumferential direction at the tread end position and a plurality of shoulder blocks spaced inward in the tire axial direction from the tread end. A middle block is provided.

In the motorcycle tire for running on rough terrain of the present invention, the land area ratio Ls1 (%) in the crown area and the land sea ratio Ls2 (%) in the middle shoulder area are expressed by the following equations (1) and (2). Satisfy the relationship.
10 <Ls1 <25 (1)
Ls1 + 3 <Ls2 <Ls1 + 10 (2)

  In such a motorcycle tire for running on rough terrain, the land area ratio in the crown region is as small as more than 10% and less than 25%, so that a large ground pressure acts on each crown block. For this reason, a crown block penetrates deeply on the road surface, and a large scratching force can be obtained. Further, the land / shoulder ratio in the middle / shoulder region is greater than 3% and less than 10% from the land region ratio in the crown region. For this reason, a middle block and a shoulder block increase a contact area with a road surface, and exhibit a big frictional force. Furthermore, the contact pressure between the crown block and the road surface decreases, and damage such as chipping is suppressed. For this reason, the motorcycle tire for running on rough terrain of the present invention improves the traction performance by effectively preventing the crown block and the middle block from exhibiting scratching and frictional forces while suppressing the chipping of the crown block. .

1 is a cross-sectional view showing a motorcycle tire for running on rough terrain according to an embodiment. FIG. 2 is a development view of the tread portion of FIG. 1. (A) is an expansion perspective view of a 1st crown block, (b) is an expansion perspective view of a 2nd crown block. (A) is an expansion perspective view of a block with a notch | incision, (b) is BB sectional drawing of (a). It is an expanded view of the tread part of other embodiment. (A) is an expansion perspective view of a block with a recessed part, (b) is CC sectional drawing of (a). It is an expanded view of the tread part of other embodiment. FIG. 3 is a cross-sectional view of a tread portion during traveling of a motorcycle tire for traveling on rough terrain.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, a motorcycle tire for motocross competition is exemplified as a motorcycle tire (hereinafter simply referred to as “tire”) 1 for traveling on rough terrain of the present embodiment. FIG. 1 is a tire meridian cross-sectional view including a tire rotating shaft in a normal state in which the tire 1 is mounted on a normal rim (not shown) and filled with a normal internal pressure and is unloaded. FIG. 2 is a development view of the tread portion 2 of the tire 1 of FIG. AA cross-sectional view of FIG. 2 is shown in FIG.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, "Measuring Rim".

  The “regular internal pressure” is the air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based, and is “maximum air pressure” for JATMA, and “TIRE LOAD” for TRA. The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  The tire 1 is located at a tread portion 2, a pair of sidewall portions 3, 3 extending inward in the tire radial direction from both sides in the tire axial direction, and inner end portions in the tire radial direction of the respective sidewall portions 3, and And bead portions 4 and 4 mounted on a rim (not shown). Further, the tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a tread reinforcing layer disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. 7 and so on.

  The outer surface of the tread portion 2 is convex and curved outward in the tire radial direction. A tread width TW which is a distance in the tire axial direction between the tread ends Te and Te of the tread portion 2 is the tire maximum width.

  The carcass 6 includes a main body portion 6a straddling a pair of bead cores 5 and 5 in a toroidal shape, and a turn-back portion 6b connected to both sides of the main body portion 6a and folded back from the inner side in the tire axial direction around the bead core 5. It is comprised from the carcass ply 6A which has. In order to reinforce the bead portion 4, a bead apex 8 made of hard rubber extends from the bead core 5 to the outer side in the tire radial direction between the main body portion 6 a and the folded portion 6 b of the carcass ply 6 </ b> A. .

  The tread reinforcing layer 7 includes, for example, one or more reinforcing plies 7A in the present embodiment, in which organic fiber reinforcing cords are inclined and arranged at an angle of 15 to 45 degrees with respect to the tire circumferential direction.

  As shown in FIGS. 1 and 2, the tread portion 2 is formed with a plurality of blocks 10 and a tread groove 11 therebetween. The groove bottom surface 11 d of the tread groove 11 is formed on a smooth surface along the outer surface of the carcass 6. The groove depth D1 of the tread groove 11 is set to 10 to 20 mm, for example.

  As shown in FIG. 2, the tread portion 2 includes a crown region 20 that is a central portion when the tread development width TWe is divided into three equal parts, and middle shoulder regions 30 and 30 on both sides thereof.

  In the crown region 20, crown blocks 21 having a substantially rectangular tread surface 22 are spaced apart in the tire circumferential direction.

  A shoulder block 32 and a middle block 31 are provided in the middle shoulder region 30. A plurality of shoulder blocks 32 are spaced apart in the tire circumferential direction at the position of the tread end Te. A plurality of middle blocks 31 are spaced apart in the tire circumferential direction at positions away from the tread end Te inward in the tire axial direction. In the present embodiment, the development length W2 between the inner edge 34 extending in the tire circumferential direction on the tire equator C side of the tread 33 of the middle block 31 and the boundary 23 of the crown region 20 is, for example, the tread development width TWe. Set to 0-9%. The middle block 31 arranged at such a position improves the steering stability during turning.

  When the block 10 crosses the boundary 23 of the crown region 20, the block 10 has the center of gravity 10 g in the crown region 20 is the crown block 21, and the block 10 has the center of gravity 10 g in the middle shoulder region 30. It is.

The land sea ratio Ls1 (%) of the crown region 20 and the land sea ratio Ls2 (%) of the middle shoulder region 30 satisfy the relationship of the following expressions (1) and (2). The land sea ratio is a ratio of the total area of the treads of the block 10 to the total area of the outer surface of the tread portion 2 when it is assumed that all of the tread grooves 11 are filled. For example, the land sea ratio Ls1 of the crown region 20 means the total area of the tread surface of the crown block 21 with respect to the entire area of the outer surface of the crown region 20 when it is assumed that the tread groove 11 is completely filled in the crown region 20. To do.
10 <Ls1 <25 (1)
Ls1 + 3 <Ls2 <Ls1 + 10 (2)

  In such a motorcycle tire for running on rough terrain, the land sea ratio Ls1 of the crown region 20 is as small as more than 10% and less than 25%, and therefore, a large ground pressure acts on each crown block. For this reason, the crown block 21 penetrates deeper into the road surface, and a large scratching force can be obtained. Further, the land / sea ratio Ls2 of the middle shoulder region 30 is larger than the land / land ratio Ls1 of the crown region by more than 3% and less than 10%. For this reason, the middle block 31 and the shoulder block 32 increase the contact area with the road surface and exhibit a large frictional force. Furthermore, the contact pressure between the crown block 21 and the road surface decreases, and damage such as chipping is suppressed. For this reason, the motorcycle tire 1 for traveling on rough terrain according to the present invention effectively suppresses the chipping of the crown block 21, while the crown block 21 and the middle block 31 each effectively exert a scratching force and a frictional force, thereby causing traction. Performance is improved.

  When the land sea ratio Ls1 of the crown region 20 is 10% or less, the block rigidity of the crown block 21 is reduced, and the crown block 21 is easily bent, so that block breakage is likely to occur and traction performance is reduced. On the contrary, when the land sea ratio Ls1 of the crown region 20 is 25% or more, the crown block 21 is difficult to pierce the road surface, so that the scratching force is hardly generated, and the traction performance is lowered. Therefore, the land sea ratio Ls1 is more preferably 13% or more, further preferably 15% or more, preferably 22% or less, more preferably 20% or less.

  When the land / sea ratio Ls2 of the middle shoulder region 30 is equal to or less than the land / sea ratio Ls1 + 3% of the crown region 20, it is not possible to prevent an excessive contact pressure from acting on the crown block 21, and the durability of the crown block 21 is increased. Sex is reduced. Furthermore, the frictional force generated by the middle block 31 and the shoulder block 32 is lowered, and the traction performance is lowered. On the contrary, when the land / sea ratio Ls2 of the middle / shoulder region 30 is equal to or greater than the land / sea ratio Ls1 + 10% of the crown region 20, mud is easily clogged between the blocks in the middle / shoulder region 30, and the traction performance particularly during turning is improved. descend. For this reason, the land sea ratio Ls2 of the middle shoulder region 30 is more preferably the land sea ratio Ls1 + 4.5% or more, further preferably the land sea ratio Ls1 + 6.0% or more, preferably the land sea ratio Ls1 + 8. 0.5% or less, more preferably 7.0% or less.

As described above, the crown block 21 generates driving force mainly by scratching force, and the middle block 31 and the shoulder block 32 generate driving force mainly by frictional force between the road surface and the tread surface. Therefore, it is desirable that each block 10 is made of an optimal rubber for exerting a driving force. That is, it is desirable that the rubber hardness Hc (degree) of the crown block 21, the rubber hardness Hm (degree) of the middle block 31, and the rubber hardness Hs (degree) of the shoulder block 32 satisfy the following relationship.
70 <Hc <80 (3)
60 <Hm <HC-3 (4)
60 <Hs <HC-3 (5)

  Thereby, the crown block 21 generates a greater scratching force. Further, the middle block 31 and the shoulder block 32 further increase the frictional force between the road surface and the tread surface and improve the traction performance.

  In addition, in this specification, rubber hardness is the hardness by durometer type A based on JIS-K6253 at the temperature of 23 degreeC.

  As shown in FIG. 1, the profile of the tread surface of each block 10 is convex and curved outward in the tire radial direction, and has a curvature radius R1 of 30 to 60% of the tread deployment width TWe. Thereby, even when the vehicle is tilted and turned, a large ground pressure acts on the middle block 31 or the shoulder block 32, and the traction performance is improved.

  Of each block 10, the profile of the tread surface of the crown block 21 and the middle block 31 preferably has a curvature radius R2 of 35 to 55% of the tread developed width TWe. As a result, after the crown block 21 has pierced the road surface at an appropriate depth, the tread surface of the middle block 31 is grounded. For this reason, the crown block 21 can exhibit a large scratching force. In addition, it is possible to suppress an excessive ground pressure from acting on the crown block 21. Accordingly, the traction performance is improved while maintaining the durability of the crown block 21.

  As shown in FIG. 2, the crown block 21 has, for example, a width W1 in the tire axial direction that is 0.15 to 0.25 times the tread deployment width TWe, and a length L1 in the tire circumferential direction that is in the tire axial direction. The width W1 is set to 0.50 to 0.70 times. In addition, the crown block 21 of the present embodiment is, for example, a first rectangular block 24 disposed on the tire equator C and a second crown divided by a slit 26 having a depth smaller than the groove 11. The crown block 25 is included.

  As shown in FIG. 3A, it is desirable that the first crown block 24 has a length L2 in the tire circumferential direction that gradually decreases from the edges 27, 27 on both sides in the tire axial direction toward the block center portion 24c. In such a first crown block 24, the substantially V-shaped end edge 28 extending in the tire axial direction and the block wall 29 connected to the end edge 28 exhibit a great scratching force and improve the traction performance.

  As shown in FIG. 3B, the second crown block 25 is composed of a pair of block pieces 19 and 19 that are divided by slits 26 extending in the tire circumferential direction and arranged on both sides of the tire equator C. Such a second crown block 25 ensures a large width W3 in the tire axial direction without increasing the area of the tread. For this reason, the second crown block 25 is deeply pierced on the road surface and exhibits a great scratching force.

  The width W3 in the tire axial direction of the second crown block 25 is preferably 1.15 times or more, more preferably 1.20 times the width W4 in the tire axial direction of the first crown block 24 (shown in FIG. 3A). It is 1 time or more, Preferably it is 1.30 times or less, More preferably, it is 1.25 times or less. In such a second crown block 25, the block wall 29 is disposed on the outer side in the tire axial direction from the first crown block 24 while maintaining the rigidity of the block, and effectively exerts a scratching force.

  As shown in FIG. 2, when the area Ac of the tread surface of the crown block 21 is small, the durability of the crown block 21 is lowered and there is a possibility that the block is chipped. On the other hand, when the area Ac of the tread surface of the crown block 21 is large, the crown block 21 does not pierce deeply into the road surface, and the scratching force is reduced, which may reduce the traction performance. For this reason, the area Ac of the tread surface of the crown block 21 is preferably larger than 1.0 times, more preferably larger than 1.5 times the area Am of the maximum tread surface in the middle block 31. In addition, the area Ac of the tread surface of the crown block 21 is preferably less than 2.5 times, more preferably less than 2.0 times the area Am of the maximum tread surface of the middle block 31. The area of the tread surface of the second crown block 25 is the total area of the tread surfaces of the block pieces 19 and 19.

  Between the first crown block 24 and the second crown block 25, it is desirable to provide a crown recess 18 in which the groove bottom surface 11d is recessed. Such a crown recessed part 18 suppresses clogging of mud in the crown region 20, and consequently improves the traction performance.

  The middle block 31 and the shoulder block 32 of the present embodiment include a block 40 with a notch. As shown in FIG. 4 (a), the block 40 with a notch includes a pair of first sipes 42 extending from the block edge 41 toward the block central portion 40c, and a second sipes that connect between the first sipes 42, 42. And a substantially U-shaped cut portion 44 formed of 43. The notched block 40 includes a sub-part 45 that is partitioned inside the notch 44 and a C-shaped main part 46 that is sectioned outside the notch 44.

  Such a notched block 40 is grounded to the road surface while the sub-part 45 is bent in accordance with the unevenness of the road surface, and thus exerts a large frictional force, thereby improving the traction performance. Moreover, such a block 40 with a notch increases an edge component to another direction, and improves especially the traction performance at the time of turning.

  In order to more effectively cause the bending of the sub-part 45 and increase the edge component of the block 40 with notches, as shown in FIG. 4B, the height h1 of the sub-part 45 is It is desirable that the height is greater than the height h2. Further, the height h1 of the sub part is preferably 1.05 times or more, more preferably 1.07 times or more, preferably 1.15 times or less, more preferably 1.12 times the height h2 of the main part. Is less than double. Thereby, the block missing of the sub part 45 is suppressed, and the edge component of the block 40 with a notch becomes large. For this reason, traction performance improves, while durability of block 40 with a notch is maintained.

  FIG. 5 shows a development view of the tread portion 2 of another embodiment. In this embodiment, only the second crown block 21 composed of a pair of block pieces 19 and 19 divided by a slit 26 extending in the tire circumferential direction is spaced on the tire equator C. Moreover, the middle block 31 and the shoulder block 32 of this embodiment are formed by the block 50 with a recessed part by which the recessed part 47 was provided in the tread surface.

  As shown in FIG. 6A, the block 50 with recesses is provided with a recess 52 in which the tread surface 51 is recessed in the central portion 50 c of the substantially pentagonal tread surface 51. In such a block 50 with a recess, when the tread surface 51 is grounded, the end edge 53 of the recess 52 exhibits an edge effect and exhibits a greater frictional force.

  As shown in FIG. 5 (b), the depth D2 of the recess 52 is preferably 5.0% or more, more preferably 7.0% or more, and preferably 15% or more of the height h3 of the block 50 with recesses. 0.0% or less, more preferably 12.0% or less. Such a block 50 with a recess exhibits a large frictional force while maintaining the durability of the block, thereby improving the traction performance.

  As shown in FIG. 7, the motorcycle tire for traveling on rough terrain of the present invention includes a first tie bar 54 in which a groove bottom surface between the crown block 21 and the middle block 31 is raised, and a tire circumferential direction. The 2nd tie bar 55 which raised the groove bottom face 11d between the adjacent shoulder blocks 32 and 32 and the middle block 31 adjacent to this shoulder blocks 32 and 32 may be provided. The first tie bar 54 and the second tie bar 55 suppress deformation at the base of the middle block 31 and the shoulder block 32 and improve the traction performance particularly on a hard uneven road surface.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

A motorcycle rear wheel tire for running on rough terrain having the basic structure shown in FIG. 1 and having the tread pattern of FIG. 2 or FIG. 5 is prototyped based on the specifications shown in Table 1, and has traction performance and block chipping resistance. Tested. The common specifications for each test tire are as follows.
Vehicle used: Displacement 450cc Motorcycle Tire size: 120 / 80-19
Rim size: 2.15 × 19
Internal pressure: 80 kPa
The test method is as follows.

<Traction performance>
The traction performance of a vehicle equipped with each test tire when running on a rough road test course was evaluated by the driver's sensory evaluation. A result is a score which sets comparative example 1 to 100, and shows that traction performance is excellent, so that a numerical value is large.

<Block durability performance>
After running the vehicle, the lack of blocks was evaluated with the naked eye. A result is a score which sets the comparative example 1 to 100, and shows that block durability performance is excellent, so that a numerical value is large.

  As a result of the test, it was confirmed that the tire of the example improved the traction performance while suppressing the block chipping.

1 Tire 2 Tread 20 Crown Area 21 Crown Block 30 Middle / Shoulder Area 31 Middle Block 32 Shoulder Block

Claims (7)

A motorcycle tire for running on rough terrain having a tread portion,
The tread portion includes a crown region that is a central portion when the tread development width is divided into three equal parts, and middle shoulder regions on both sides thereof,
In the crown area, a plurality of crown blocks are spaced apart in the tire circumferential direction,
The middle shoulder region includes a plurality of shoulder blocks spaced in the tire circumferential direction at the tread end position, and a plurality of shoulder blocks spaced in the tire axial direction from the tread end in the tire circumferential direction. Middle blocks are provided,
Rough terrain traveling characterized in that the land sea ratio Ls1 (%) of the crown area and the land sea ratio Ls2 (%) of the middle shoulder area satisfy the relationship of the following expressions (1) and (2): Motorcycle tires.
10 <Ls1 <25 (1)
Ls1 + 3 <Ls2 <Ls1 + 10 (2)   The tire for motorcycles for rough terrain travel according to claim 1, wherein an area Ac of the tread of each crown block is greater than 1.0 and less than 2.5 times the area Am of the maximum tread of the middle block. .   The tire for motorcycles for rough terrain travel according to claim 1 or 2, wherein the crown block includes a first crown block disposed on the tire equator.   The said crown block contains the 2nd crown block which consists of a pair of block piece divided | segmented by the slit extended in the tire circumferential direction, and was distribute | arranged on the both sides of the tire equator. Motorcycle tires for leveling. The tread of the middle block includes an inner edge extending in the tire circumferential direction on the tire equator side,
The tire for motorcycles for rough terrain travel according to any one of claims 1 to 4, wherein a development length between the inner edge and a boundary of the crown region is 0 to 9% of the tread development width. . In the tire meridian cross section including the tire rotation axis in the normal state where the rim is assembled to the normal rim and the normal internal pressure is filled and the no load is applied,
The motorcycle tire for rough terrain travel according to any one of claims 1 to 5, wherein the profile of the tread surface of the crown block and the middle block has a curvature radius of 35 to 55% of the tread developed width. The rubber hardness Hc (degree) of the crown block, the rubber hardness Hm (degree) of the middle block, and the rubber hardness Hs (degree) of the shoulder block satisfy the relationship of the following formulas: Motorcycle tires for traveling on rough terrain as described in any one of the above.
70 <Hc <80 (3)
60 <Hm <HC-3 (4)
60 <Hs <HC-3 (5)

Images