Motorcycle tires for off-road riding

Abstract

To provide a motorcycle tire 1 for off-road traveling excellent in grip performance.SOLUTION: A tread part 2 of a tire 1 comprises: a plurality of shoulder blocks 11 forming a tread end Te; and a plurality of middle blocks 12 adjacent to the shoulder blocks 11 at a tire axial direction inner side. A lateral face SU of the shoulder block 11 at the tire axial direction inner side includes: a first lateral face SU1 which extends from an inner edge 11B toward a groove bottom; and a second lateral face SU2 which extends from a bottom side end of the first lateral face SU1 toward the groove bottom. The second lateral face SU2 is a slant face at the tire axial direction inner side relative to the first lateral face SU1. A ratio (Sa / Sb) of a crest part area Sa where a bottom side end SS of the first lateral face SU1 is an apex to a body area Sb including an inner edge 11B is 5% or more.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a tire for a motorcycle. More specifically, it relates to a tire suitable for a motorcycle traveling on rough ground.

Background Art

[0002] A motorcycle tire for rough ground driving tends to be used under a lower internal pressure compared to a tire for paved road driving. In particular, tires for trial competitions on rough ground are used at a low internal pressure of about 30 to 40 kPa, for example. Therefore, in a motorcycle tire for rough ground driving, the tread portion easily deforms according to the unevenness of the road surface. As a result, a large contact pressure acts on each of the shoulder blocks and the middle blocks, and these blocks contribute to the exhibition of grip performance.

[0003] Patent Document 1 describes a method for improving grip performance by increasing the contact pressure during load application by protruding the shoulder block outward from the tread surface in the above-mentioned motorcycle tire.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a large camber angle is applied to the tire, the contact pressure increases at the inner edge of the shoulder block. As described above, the tread portion easily deforms. When a high load acts on the shoulder block, there is a risk that the shoulder block may fall too much toward the tread center side. In this case, the tire cannot exhibit sufficient grip performance. A large camber angle refers to a state where the tire is tilted relative to the road surface to such an extent that the ground surface of the shoulder block is included in the contact patch.

[0006] As a result of various experiments, the inventors discovered that the above-mentioned problems could be solved by thickening the base of the shoulder block to suppress the tilting of the shoulder block, and thus completed the present invention.

[0007] In view of the above circumstances, the present invention aims to provide a motorcycle tire for off-road riding that can exhibit excellent grip performance. [Means for solving the problem]

[0008] A tire for a motorcycle for off-road driving according to one aspect of the present invention has a tread portion. The tread portion comprises a plurality of blocks that rise from the bottom surface of the groove. The plurality of blocks include a plurality of shoulder blocks that form the tread end and a plurality of middle blocks adjacent to the shoulder blocks on the inner side in the tire axial direction. The inner side surface of the shoulder block in the tire axial direction includes a first side surface extending toward the groove bottom from the inner edge of the ground surface of the shoulder block in the tire axial direction and a second side surface extending toward the groove bottom from the bottom end of the first side surface. The second side surface is a surface inclined inward in the tire axial direction with respect to the first side surface. In a meridional cross section including the tire rotation axis, the line segment connecting the bottom end of the first side surface and the bottom end of the outer side surface of the shoulder block in the tire axial direction is the first reference line, and the line segment connecting the groove bottom between the shoulder block and the middle block to the first reference line and tangent to the groove bottom surface at the groove bottom is the second reference line. When the area enclosed by the land surface of the shoulder block, the first side surface, the first reference line, and the outer side surface is defined as the main body area, and the area enclosed by the second side surface, the second reference line, and the first reference line is defined as the mountain area, the ratio of the mountain area to the main body area is 5% or more.

[0009] Preferably, in this off-road motorcycle tire, the angle between the first reference line and the second side surface is 40° or more and 170° or less.

[0010] Preferably, in this off-road motorcycle tire, the ratio of the axial distance from the tire's equatorial plane to the bottom edge of the first side surface to the axial distance from the tire's equatorial plane to the tread edge is 65% or more.

[0011] Preferably, in this off-road motorcycle tire, in the meridian cross-section, the inner edge of the shoulder block protrudes radially outward from the virtual profile obtained by extending the land surface profile of the middle block to the shoulder block, and the amount of protrusion from the virtual profile is 0.5 mm or more.

[0012] Preferably, in this off-road motorcycle tire, the hardness of the tread portion at 25°C is 40 to 70. [Effects of the Invention]

[0013] According to the present invention, a motorcycle tire for off-road riding that can exhibit excellent grip performance can be obtained. [Brief explanation of the drawing]

[0014] [Figure 1] This is a cross-sectional view of a tire according to an embodiment of the present invention. [Figure 2] Figure 1 is an exploded view of the tire tread. [Figure 3] Figure 1 shows an enlarged cross-sectional view of the middle block and shoulder block of the tire. [Figure 4] This is a cross-sectional view of a conventional tire during driving. [Figure 5] This is a cross-sectional view of a tire during driving according to an embodiment of the present invention. [Modes for carrying out the invention]

[0015] Hereinafter, embodiments of the present invention will be described based on the drawings. In FIG. 1, as an example of a motorcycle tire for rough terrain driving (hereinafter also simply referred to as "tire") 1, a rear tire for trial competition is illustrated. The tire 1 is used, for example, in a state filled with a low internal pressure of 30 to 40 kPa.

[0016] FIG. 1 is a tire meridian cross-sectional view including the tire rotation axis in the normal state of the tire 1. FIG. 2 is a development view of the tread portion 2 of the tire 1 in FIG. 1. The cross-sectional view taken along line A-A in FIG. 2 is shown in FIG. 1.

[0017] The "normal state" is a no-load state in which the tire is assembled to a normal rim and the internal pressure of the tire is adjusted to the normal internal pressure. Hereinafter, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in this normal state.

[0018] The "normal rim" is a rim defined for each tire in a standard system including the standard on which the tire is based. For example, in the case of JATMA, it means the standard rim, in the case of TRA, it means "Design Rim", or in the case of ETRTO, it means "Measuring Rim".

[0019] The "normal internal pressure" is the air pressure defined for each tire by the said standard. In the case of JATMA, it means the maximum air pressure, in the case of TRA, it means the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it means "INFLATION PRESSURE".

[0020] As shown in FIG. 1, the tire 1 has, for example, a carcass 6 and a belt layer 7 in addition to the tread portion 2. The carcass 6 is configured, for example, in a toroidal shape that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 embedded in the bead portion 4. The belt layer 7 is positioned, for example, on the radially outer side of the carcass 6 and inside the tread portion 2, reinforcing the tread portion 2. These carcass 6 and belt layer 7 can preferably utilize known configurations.

[0021] The dashed line CL in Figure 1 represents the equatorial plane of tire 1. The position indicated by the symbol C is the intersection of the tread surface 8 and the equatorial plane. Intersection C is the equator of tire 1 (tire equator).

[0022] The outer surface between the two tread ends Te of the tread section 2 (which are also the outer edge 11A in the tire axial direction of the ground surface of the shoulder block 11 described later), i.e., the tread surface 8, is convex outward in the tire radial direction and curves in an arc shape. Multiple blocks 10 are formed in the tread portion 2, rising from the groove bottom surface 9. The tread portion 2 comprises multiple blocks 10. The tread surface 8 includes the land surface of the block 10. The portion of the tread surface 8 other than the land surface is the groove 17.

[0023] The tread portion 2 is made of cross-linked rubber. The tread portion 2 of this tire 1 is made of a single rubber composition. All the blocks 10 provided on the tread portion 2 are made of the same cross-linked rubber. In this tire 1, the tread portion 2 may be configured such that the material of the part containing the blocks 10 is different from the material of the other parts.

[0024] The tread edge Te refers, for example, to the outermost edge in the tire axial direction of block 11, which is the block 10 that is located furthest outward in the tire axial direction among the blocks 10 formed on the tread portion 2.

[0025] As shown in Figure 2, the tread portion 2 includes, for example, a first region 14, a second region 15, and a third region 16. The first region 14 is a region extending 25% of the tread width TWh from the tread edge Te. The second region 15 has a width of 50% of the tread deployment half width TWh, and its center is located at the tire equator C. The third region 16 is the region between the first region 14 and the second region 15. The tread deployment half width TWh is the distance from the tire equator C to the tread edge Te when the tread portion 2 is deployed.

[0026] Block 10 includes, for example, a shoulder block 11, a middle block 12, and a crown block 13. The shoulder block 11 is a block that forms the tread edge Te, with its centroid located in the first region 14. The middle block 12 is a block with its centroid located in the third region 16. The crown block 13 is a block with its centroid located in the second region 15. In the tire 1 of this embodiment, the crown block 13 is positioned, for example, on the tire equator C.

[0027] As shown in Figure 2, in this tire 1, multiple shoulder blocks 11 are arranged at intervals in the circumferential direction. The space between two shoulder blocks 11 aligned in the circumferential direction is the groove bottom surface 9. Multiple middle blocks 12 are arranged at intervals in the circumferential direction. The space between two middle blocks 12 aligned in the circumferential direction is the groove bottom surface 9. Multiple crown blocks 13 are arranged at intervals in the circumferential direction. The space between two crown blocks 13 aligned in the circumferential direction is the groove bottom surface 9.

[0028] The middle block 12 is adjacent to the shoulder block 11 on the tire axial side. The middle block 12 overlaps with at least the region of the shoulder block 11 extended in the tire axial direction. In this tire 1, the circumferential end of the shoulder block 11 and the circumferential end of the middle block 12 overlap in the axial direction. In the tire 1 of this embodiment, the centroid of the middle block 12 is offset in the circumferential direction of the tire from the centroid of the shoulder block 11. However, the tire 1 of the present invention is not limited to this form.

[0029] Figure 3 is an enlarged cross-sectional view of the middle block 12 and the shoulder block 11. As shown in Figure 3, in a meridian cross-section including the tire rotation axis in the normal state, the inner edge 11B of the ground surface of the shoulder block 11 in the tire axial direction protrudes radially outward from the virtual profile 18 obtained by extending the ground surface profile of the middle block 12 to the shoulder block 11.

[0030] In this tire 1, the inner edge 11B may be included in the virtual profile 18. However, by making the shoulder block 11 protrude as shown in the figure, the contact pressure at road surface contact can be increased, improving grip. In addition, the inner edge 11B of the shoulder block 11 provides greater grip. From this viewpoint, it is preferable that the inner edge 11B protrudes radially outward from the virtual profile 18. In this case, the amount P of the protrusion of the inner edge 11B from the virtual profile 18 is preferably 0.5 mm or more and 5.0 mm or less.

[0031] If the protrusion amount P is less than 0.5 mm, the increase in contact pressure is small and grip cannot be secured. Also, if the protrusion amount is greater than 5.0 mm, the shoulder block 11 protrudes too much, and when further load is applied, the middle block 12 lifts off the road surface, resulting in a significant decrease in grip. The protrusion amount P is more preferably 2.5 mm or more, even more preferably 3.0 mm or more, more preferably 4.5 mm or less, and even more preferably 4.0 mm or less.

[0032] As shown in Figure 3, the inner side surface SU of the shoulder block 11 in the tire axial direction (synonymous with the tread center side) includes the following two sides SU1 and SU2. Of these, the second side surface SU2 is a surface that is inclined toward the tread center side relative to the first side surface SU1. First side surface SU1: A plane extending from the inner edge 11B toward the bottom of the groove. Second side surface SU2: A single plane extending from the bottom edge of the first side surface SU1 toward the bottom of the groove.

[0033] In Figure 3, the symbol SS is the intersection of the line containing the first side surface SU1 and the line containing the second side surface SU2. This intersection SS is the bottom end of the first side surface SU1. Side surface SU bends at the bottom end SS. The symbol SE is the intersection of the outer side surface SG in the tire axial direction of the shoulder block 11 and the groove bottom surface 9. Intersection SE is the bottom end of side surface SG. Line L1 is a line segment connecting the bottom end SS of the first side surface SU1 and the bottom end SE of the outer side surface SG. In this disclosure, this line segment L1 is the first reference line.

[0034] In Figure 3, the symbol SB represents the groove bottom between the shoulder block 11 and the middle block 12. The symbol MB represents the groove bottom between the middle block 12 and the crown block 13. The groove bottoms SB and MB are included in the groove bottom surface 9. In the meridional section, the profile of the groove bottom surface 9 passes through the groove bottoms SB and MB. The line L2 connects the groove bottom SB to the first reference line L1 and is a line segment tangent to the groove bottom surface 9 at the groove bottom SB. In this disclosure, this line segment L2 is the second reference line.

[0035] In this disclosure, the area of ​​the region enclosed by the land surface, the first side surface SU1, the first reference line L1, and the outer side surface SG of the shoulder block 11 is the main body area Sb, and the area of ​​the region enclosed by the second side surface SU2, the second reference line L2, and the first reference line L1 is the mountain area Sa.

[0036] Figure 4 is a cross-sectional view of a conventional tire during driving. In conventional tires, the inner side of the shoulder block a is usually composed of a single surface. The rigidity of the base of the shoulder block a is low, and when a load is applied, the tire begins to bend, especially from the base of the shoulder block a. Therefore, when a large camber angle is applied to the tire and a high load is acted on the shoulder block a, as shown in Figure 4, the tire tends to tilt inward towards the middle block b (i.e., towards the tire center), and the inner edge c of the shoulder block a lifts up. In this case, a lack of grip occurs because the ground surface of the shoulder block a does not make contact.

[0037] In contrast, in this tire 1, as mentioned above, the inner side surface SU of the shoulder block 11 includes a first side surface SU1 and a second side surface SU2, and the second side surface SU2 is configured as a surface inclined toward the tread center with respect to the first side surface SU1. In other words, the center side surface S of the shoulder block 11 is composed of two or more surfaces SU1, SU2 toward the groove bottom SB. Therefore, the base portion of the shoulder block 11 has a shape that gradually widens toward the groove bottom SB. In particular, in this tire 1, the ratio of the ridge area Sa to the main body area Sb (Sa / Sb) is 5% or more. Therefore, the rigidity of the base portion of the shoulder block 11 is effectively increased, and the base portion is effectively reinforced. As a result, this tire 1 can suppress bending at the base portion of the shoulder block 11 when a load is applied, and can prevent the block from collapsing inward.

[0038] Figure 5 is a cross-sectional view of the tire 1 of this embodiment during driving. As shown in Figure 5, in the tire 1 of this embodiment, the shoulder block 11 has a base portion in which the width gradually increases toward the tire center due to the two-stage side SU1, SU2. As a result, a large camber angle is applied to the tire 1, and even when a high load is applied to the shoulder block 11, inward tilting of the shoulder block 11 toward the tire center does not occur or is unlikely to occur. Therefore, the ground surfaces of both the shoulder block 11 and the middle block 12 make sure contact with the road surface, and the inner edge 11B of the shoulder block 11 and the outer edge 12A of the middle block 12 can provide sufficient grip for this tire 1. This tire 1 can exhibit excellent grip performance.

[0039] As mentioned above, in this tire 1, the shoulder block 11 has a moderate amount of protrusion P. Compared to a shoulder block whose inner edge does not protrude, a high load is applied to this shoulder block 11. However, in this tire 1, as mentioned above, the base portion of the shoulder block 11 effectively suppresses the occurrence of inward tilting of the shoulder block 11. In this tire 1, the inner edge 11B of the shoulder block 11 protrudes moderately. Therefore, even though a high load is applied to this shoulder block 11, a large camber angle is given to the tire 1, and even when a high load is applied to the shoulder block 11, inward tilting of the shoulder block 11 toward the tire center does not occur or is unlikely to occur. On the contrary, because the shoulder block 11 has a moderate protrusion P, when a large camber angle is applied to the tire 1, the shoulder block 11 makes contact with the road surface first, effectively increasing the contact pressure. This tire 1 can achieve a dramatic improvement in grip when a load is applied.

[0040] As mentioned above, in this tire 1, the ratio of the tread area Sa to the main body area Sb (Sa / Sb) is 5% or more. From the viewpoint of preventing the shoulder block 11 from collapsing inward, it is more preferable that this ratio (Sa / Sb) be 6% or more. From the viewpoint of maintaining good grip performance while preventing a decrease in absorption when a load is applied, it is preferable that this ratio (Sa / Sb) be 10% or less, and more preferable that it be 7% or less.

[0041] In Figure 3, the symbol θ1 represents the angle between the first reference line L1 and the second side surface SU2 in the meridian cross-section. In this tire 1, the angle θ1 is preferably between 40° and 170°. This effectively suppresses inward tilting of the shoulder block 11 while preventing a decrease in absorption performance under load. From this viewpoint, the angle θ1 is more preferably 80° or more, more preferably 120° or less, and even more preferably 100° or less. Furthermore, if the angle θ1 is less than 40°, the rigidity of the base of the shoulder block 11 may be insufficient, causing the shoulder block 11 to tilt inward under load, potentially reducing grip performance. If the angle θ1 is greater than 170°, the rigidity of the base of the shoulder block 11 may become too high, potentially significantly reducing its ability to absorb loads.

[0042] In Figure 3, the sign θ2 is the angle between the first virtual surface 19, which is an extension of the first side surface SU1 in the radial direction of the tire, and the second side surface SU2. The angle θ3 is the angle between the first side surface SU1 and the second virtual surface 20, which connects the outer edge 11A and the inner edge 11B in the tire axial direction of the tread surface of the shoulder block 11.

[0043] In this tire 1, the angle θ2 is preferably greater than 0°, more preferably 30° or more, preferably less than 90°, and more preferably 80° or less, from the viewpoint of optimizing the rigidity of the base portion of the shoulder block 11 and improving grip performance without impairing load absorption.

[0044] In this tire 1, the angle θ3 is preferably 50° or more, more preferably 55° or more, more preferably 120° or less, and more preferably 80° or less, from the viewpoint of optimizing the rigidity of the base portion of the shoulder block 11 and improving grip performance without impairing load absorption.

[0045] In Figure 3, the length indicated by the symbol WE is the axial half width of the tread section 2. The axial half width WE is the axial distance from the equatorial plane to the tread edge Te. The length indicated by the symbol WS is the axial distance from the equatorial plane to the bottom edge SS of the first side surface SU1.

[0046] In this tire 1, it is preferable that the ratio of the axial distance WS to the axial half width WE of the tread portion 2 (WS / WE) is 65% or more. This ensures that the base portion of the shoulder block 11, which is formed as a peak with the bottom edge SS as its apex, is positioned appropriately. When a large camber angle is applied to the tire 1, the base portion can effectively contribute to suppressing the inward tilting of the shoulder block 11. In this tire 1, even when a high load is applied to the shoulder block 11, the inward tilting of the shoulder block 11 is effectively suppressed. This tire 1 can exhibit good grip performance. From this viewpoint, the ratio (WS / WE) is more preferably 70% or more. The upper limit of this ratio (WS / WE) is determined appropriately considering the position of the inner edge 11B of the shoulder block 11, but from the viewpoint that the ground surface of the shoulder block 11 can be formed of an appropriate size, it is preferable that this ratio (WS / WE) is 85% or less.

[0047] In Figure 3, the length indicated by the symbol W1 is the width of the land surface of the shoulder block 11. This width W1 is represented by the length of the line segment connecting the outer edge 11A and the inner edge 11B of the shoulder block 11. The length indicated by the symbol W2 is the width of the land surface of the middle block 12. This width W2 is represented by the length of the line segment connecting the outer edge 12A and the inner edge 12B of the middle block 12.

[0048] In this tire 1, the width W1 of the ground surface of the shoulder block 11 is preferably narrower than the width W2 of the ground surface of the middle block 12. More preferably, the ratio of width W1 to width W2 is 0.70 or more and 0.85 or less. Such shoulder blocks 11 are easily deformable to a moderate degree, which helps to increase the contact pressure acting on the middle blocks 12. This tire 1 can achieve further improvement in grip performance. The width W1 of the ground surface of the shoulder blocks 11 is set within the range of 15% to 25% of the tread width TWh as described above.

[0049] In this tire 1, the hardness Hs of the tread portion 2 at 25°C is preferably 40 to 70. If the hardness Hs is less than 40, the block 10 is too soft and cannot prevent the shoulder block 11 from collapsing inward under load. On the other hand, if Hs is greater than 70, the rigidity of the base portion of the shoulder block 11 becomes significantly higher, worsening its shock absorption. The hardness Hs of the tread portion 2 is more preferably 40 or higher, and more preferably 55 or lower.

[0050] In this disclosure, the hardness of the cross-linked rubber elements among the components constituting the tire is measured using a Type A durometer under a temperature of 25°C in accordance with the provisions of JIS K6253. In this tire 1, the hardness of the block 10 is measured by bringing the Type A durometer into contact with the block 10.

[0051] As shown in Figure 2, in the tire 1 of this embodiment, the inner edge 11B of each shoulder block 11 extends parallel to the circumferential direction of the tire. In this case, when a load is applied, the entire inner edge 11B of the shoulder block 11 tends to come into contact with the road surface, resulting in uniform contact pressure on the ground surface of the shoulder block 11 and improved grip performance. Furthermore, inward tilting of the shoulder block 11 can be prevented by the entire inner edge 11B, thus suppressing the reduction in grip performance due to inward tilting. From this viewpoint, it is preferable that the inner edge 11B of the shoulder block 11 extends parallel to the circumferential direction of the tire.

[0052] The configuration and operation of a motorcycle tire for off-road driving according to one embodiment of the present invention have been described above. However, the present invention is not limited to the above-described embodiment and can be implemented in various modified forms. For example, in the embodiment described above, the second side surface S2 is composed of a single plane, but the second side surface S2 may be composed of multiple planes in a multi-stage configuration. Alternatively, the second side surface S2 may be a concave curved surface without a flat portion. In this case, the angles θ1 and θ2 described above are measured using the line segment connecting the bottom end SS of the first side surface SU1 and the groove bottom SB as the second side surface SU2. [Examples]

[0053] A prototype rear tire for trial competitions, having the basic structure shown in Figure 1 and the tread pattern shown in Figure 2, was manufactured based on the specifications in Table 1. A bias-ply carcass was used for the tire. As Comparative Example 1, a tire with a single sidewall S (i.e., a ratio (Sa / Sb) of 0%) was prototyped. Except for this point, the tire of Comparative Example 1 had the same configuration as in Figures 1 and 2. For each test tire, the grip performance of the tire was tested under high load with a large camber angle applied. The common specifications and test methods for each test tire are as follows.

[0054] Vehicle used: 300cc motorcycle specifically designed for trial competitions. Tire size: 120 / 100-R18 (rear wheel) Rim size: 2.15 x 18 (rear wheel) Internal pressure: 30kPa The testing method is as follows:

[0055] <Grip performance under high camber and heavy load conditions> Vehicles fitted with each test tire were driven on a trial course by riders, and the grip performance was evaluated subjectively by the riders when a large camber angle was applied and a high load was acted upon the test tires. The results were scored on a scale of 10 points, with higher scores indicating better grip performance at high camber and high loads. The test results are shown in Table 1.

[0056] [Table 1]

[0057] The test results confirmed that the tires in the example exhibited excellent grip performance under high camber and high load conditions. [Explanation of symbols]

[0058] 1 tire 2 Tread section 9 Groove bottom surface 10 blocks 11 Shoulder Block 11A Outer edge 11B Inner Edge 12 Middle Block 18 Virtual Profiles 19. First Virtual Surface 20 Second Virtual Surface Te tread edge SU side SU1 1st side SU2 Second side L1 First reference line L2 Second reference line

Claims

1. A motorcycle tire for off-road riding having a tread section, The tread portion comprises a plurality of blocks that rise from the bottom surface of the groove, The plurality of blocks include a plurality of shoulder blocks that form the tread edge and a plurality of middle blocks adjacent to the inner side of the shoulder blocks in the tire axial direction, The inner side surface of the shoulder block in the tire axial direction includes a first side surface extending from the inner edge of the ground surface of the shoulder block in the tire axial direction toward the bottom of the groove, and a second side surface extending from the bottom end of the first side surface toward the bottom of the groove, wherein the second side surface is inclined inward in the tire axial direction with respect to the first side surface. In a meridian cross-section including the tire rotation axis, the line segment connecting the bottom end of the first side surface and the bottom end of the outer side surface of the shoulder block in the tire axial direction is the first reference line, and the line segment connecting the groove bottom between the shoulder block and the middle block to the first reference line, and tangent to the groove bottom surface at the groove bottom, is the second reference line. The angle between the first virtual surface, which is an extension of the first side surface in the radial direction of the tire, and the second side surface is 30° or more and less than 90°. When the area of ​​the region enclosed by the land surface of the shoulder block, the first side surface, the first reference line, and the outer side surface is defined as the main body area, and the area of ​​the region enclosed by the second side surface, the second reference line, and the first reference line is defined as the mountain area, The ratio of the area of ​​the mountain portion to the area of ​​the main body is 5% or more. Motorcycle tires designed for off-road riding.

2. The angle between the first reference line and the second side surface is 40° or more and 170° or less. A motorcycle tire for off-road riding as described in claim 1.

3. The ratio of the axial distance from the tire's equatorial plane to the bottom edge of the first side surface to the axial distance from the tire's equatorial plane to the tread edge is 65% or more. A motorcycle tire for off-road riding according to claim 1 or 2.

4. In the meridian cross-section, the inner edge of the shoulder block protrudes radially outward from the virtual profile obtained by extending the land surface profile of the middle block to the shoulder block. The amount of protrusion from the virtual profile is 0.5 mm or more. A motorcycle tire for off-road riding according to any one of claims 1 to 3.

5. The hardness of the tread portion at 25°C is 40 to 70. A motorcycle tire for off-road riding according to any one of claims 1 to 4.

6. The tire for a motorcycle for off-road riding according to any one of claims 1 to 5, wherein the outer side surface of the middle block in the tire axial direction includes a plane extending from the outer edge of the tread surface of the middle block in the tire axial direction toward the bottom of the groove.

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