Motorcycle tyre for off-road use

Abstract

The present invention provides a motorcycle tire for uneven ground travel with superior grip at low load. The tire has a block pattern. The block pattern includes a plurality of connected block pairs. Each connected block pair has two blocks (28), and a tie (30) sandwiching and connecting the blocks (28). The tie (30) has a rear ground contact side end (40) having a height equal to or less than that of the blocks (28), and a front ground contact side end (38) having a height less than that of the rear ground contact side end (40).

Description

TECHNICAL FIELD

[0001] The present application relates to a tire for a motorcycle that runs on uneven ground. In detail, the present application relates to an improvement of a tread of the tire. BACKGROUND

[0002] A motorcycle tire that runs on uneven ground is provided with a tread having a block pattern. The block pattern includes a groove and a plurality of blocks. Each block stands from the groove. In a soft road surface, the blocks pierce into the road surface. By an edge effect of the blocks, the tire exhibits superior traction performance in a soft road surface.

[0003] In a hard road surface, the blocks pierce into the road surface less. The rigidity of the blocks governs the contribution to the traction performance in a hard road surface. A tread with large rigidity is desired.

[0004] A tire in which two blocks that are adjacent to each other are connected by a tie bar is known. The height of the tie bar is smaller than the height of the blocks. The tie bar can contribute to the rigidity of the tread. One example of the tire with the tie bar is disclosed in Japanese Patent Application Publication No. 2012-030658 (Japanese Patent No. 5174095).

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-030658

[0006] As described above, the height of the tie bar is smaller than the height of the blocks. However, the tie bar is higher than the groove. Therefore, the tie bar can hinder the piercing of the blocks in a soft road surface. In a scenario in which the load applied to the tire is low, the force that presses the tire against the ground is weak. In this scenario, the tie bar particularly hinders the piercing of the blocks. The tie bar can be a factor that deteriorates the grip of the tire. SUMMARY

[0007] An object of the present application is to provide a motorcycle tire for running on uneven ground that has a tie bar that can contribute to rigidity and also has superior grip in a low load.

[0008] A motorcycle tire for running on uneven ground according to the present application is provided with a tread having a block pattern. The block pattern has a groove, a plurality of blocks that respectively stand from the groove and have lands, and a plurality of tie bars that respectively stand from the groove. In the block pattern, a pair of blocks having two blocks that are adjacent to each other is formed. The pair of blocks includes a plurality of connected pairs of blocks. Each connected pair of blocks has two blocks and a tie bar that is sandwiched by the blocks and connects the blocks. In the connected pair of blocks, the tie bar has a rear ground-contacting side end that has a height that is the same as or smaller than the height of the blocks, and a front ground-contacting side end that has a height that is smaller than the height of the rear ground-contacting side end.

[0009] Preferably, the ribs have a height that gradually increases from the leading-landing-side end toward the trailing-landing-side end.

[0010] Preferably, the angle of the line connecting the leading-landing-side end and the trailing-landing-side end with respect to the circumferential direction is 2° or more.

[0011] Preferably, the ratio H2 / Hb of the height H2 of the trailing-landing-side end of the pair of block-joining blocks to the height Hb of the block is 0.20 or more and 0.95 or less.

[0012] The tread has a crown region in the axial center, a pair of intermediate regions on the axial outer sides of the crown region, and a pair of shoulder regions on the axial outer sides of the intermediate regions. Preferably, the ratio N1 / N of the number N1 of the pair of block-joining blocks in the crown region in which the height of the trailing-landing-side end is greater than the height of the leading-landing-side end to the number N of the pairs of blocks is 0.10 or more.

[0013] Preferably, the land ratio of the block pattern is 13% or more and 60% or less.

[0014] Preferably, the JIS-A hardness of the pair of block-joining blocks is 45 or more and 88 or less.

[0015] The tire can be mounted to a front wheel rim of a motorcycle.

[0016] The uneven-ground-riding motorcycle tire according to the present application has ribs, and also has superior grip performance at low load. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is an expanded view showing a portion of the uneven-ground-riding motorcycle tire according to one embodiment of the present application.

[0018] Figure 2 is an enlarged cross-sectional view taken along the line II-II of Figure 1

[0019] Figure 3 is a perspective view showing a first pair of blocks of the tire of Figure 1

[0020] Figure 4 is a plan view showing the first pair of blocks of Figure 3

[0021] Figure 5 is a cross-sectional view taken along the line V-V of Figure 4

[0022] Figure 6 is a cross-sectional view taken along the line VI-VI of Figure 4 ​​​​​

[0023] Explanation of reference signs

[0024] 2 … motorcycle tire for rough terrain; 4 … tread; 18 … base; 20 … top; 26 … groove; 28, 28a, 28b … block; 30 … rib; 32 … land; 34 … side; 36 … top; 37 … side; 38 … leading side end; 40 … trailing side end; P1 … first block pair; P2 … second block pair; P3 … third block pair; P4 … fourth block pair; Zc … crown region; Zm … middle region; Zs … shoulder region. DETAILED DESCRIPTION

[0025] Hereinafter, the present application will be described in detail based on a preferred embodiment, with appropriate reference to the accompanying drawings.

[0026] Figure 1 and Figure 2 A motorcycle tire 2 is shown. The tire 2 is adapted for running in rough terrain such as mountains, wilderness, and the like. The tire 2 is provided with a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 12, a chafer 14, and an inner liner 16. In Figure 1 and Figure 2 In the drawings, reference sign X indicates an axial direction, reference sign Y indicates a circumferential direction, and reference sign Z indicates a radial direction. However, in the expanded view of Figure 1 , the surface (curved surface) of the tire 2 is planarized. Figure 2 In the drawings, a dashed line Eq indicates an equatorial plane of the tire 2. The tire 2 is in a substantially mirror-symmetrical shape with the equatorial plane Eq as a center. In the present embodiment, the tire 2 is mounted to a front wheel rim of a motorcycle. The tire 2 of the present application can also be mounted to a rear wheel rim of a motorcycle.

[0027] The tread 4 is in a shape protruding to the radially outer side. The tread 4 is composed of a base 18 and a top 20. The base 18 is composed of crosslinked rubber. The top 20 is located radially outside the base 18. The top 20 is composed of crosslinked rubber.

[0028] The sidewall 6 extends from the end of the tread 4 to the radially substantially inner side. The sidewall 6 is composed of crosslinked rubber. The sidewall 6 absorbs the impact from the road surface by flexing. In addition, the sidewall 6 prevents the outer damage of the carcass 10. In the present embodiment, the material of the sidewall 6 is the same as that of the base 18. The sidewall 6 is formed integrally with the base 18.

[0029] The bead 8 is located at a position radially substantially inside the sidewall 6. The bead 8 is provided with a core 22 and a triangular rubber 24 extending from the core 22 to the radially outer side. The core 22 is in a ring shape. In the core 22, a non-elastic wire is wound multiple times. A typical material of the non-elastic wire is steel. The triangular rubber 24 is tapered toward the radially outer side. The triangular rubber 24 is composed of crosslinked rubber with high hardness.

[0030] The carcass 10 is erected between the two side beads 8, extends along the inner side of the tread 4 and the sidewall 6. The carcass 10 is laminated to the inner liner 16. The carcass 10 is folded back from the axial inner side toward the outer side around the core 22. The carcass 10 is composed of one ply. The number of plies of the carcass 10 can be two or more.

[0031] Although not shown, the carcass 10 includes a plurality of cords and a rubber in parallel. Each cord is obliquely crossed with respect to the equatorial plane Eq. The cord can also be actually orthogonal with respect to the equatorial plane Eq. A typical cord is composed of an organic fiber. As a preferable organic fiber, a polyester fiber, a nylon fiber, a rayon fiber, a polyethylene naphthalate fiber, and an aramid fiber are exemplified.

[0032] The belt 12 is located radially outside the carcass 10. The belt 12 is laminated to the carcass 10. The belt 12 reinforces the carcass 10. The belt 12 is composed of one layer. The number of layers of the belt 12 can be two or more. Although not shown, the belt 12 includes a plurality of cords and a rubber in parallel. Each cord is obliquely crossed with respect to the equatorial plane Eq. The absolute value of the oblique angle is 10° or more and 35° or less. A typical cord is composed of an organic fiber. The material of the cord can also be steel.

[0033] Figure 1 A portion of the tread pattern is shown. The tread pattern is repeated in the circumferential direction throughout the tire 2. In the present embodiment, the tread pattern is mirror-symmetric with respect to the equatorial plane Eq. The tread pattern can also be asymmetric with respect to the equatorial plane Eq.

[0034] Figure 1 The arrow Wp in FIG. 1 indicates the periphery length of the tread 4. The tread 4 can be divided into a crown region Zc, a pair of intermediate regions Zm, and a pair of shoulder regions Zs. The periphery length of the crown region Zc is 1 / 3 of the periphery length Wp of the tread 4. The periphery length of each intermediate region Zm is 1 / 6 of the periphery length Wp of the tread 4. The total periphery length of the two intermediate regions Zm is 1 / 3 of the periphery length Wp of the tread 4. The periphery length of each shoulder region Zs is 1 / 6 of the periphery length Wp of the tread 4. The total periphery length of the two shoulder regions Zs is 1 / 3 of the periphery length Wp of the tread 4.

[0035] The tread pattern has a plurality of grooves 26 and a plurality of blocks 28. Each block 28 stands from a groove 26. The tread pattern is called a block pattern. The tread pattern also has a plurality of ribs 30. Each rib 30 stands from a groove 26.

[0036] As shown in FIG. 1, the tire 2 has a pair of beads 8, a carcass 10, a belt 12, a core 22, a tread 4, and an inner liner 16. Figure 1As is clear, the block 28 and the cord 30 exist in the crown region Zc. The block 28 exists in the middle region Zm. The cord 30 does not exist in the middle region Zm. The block 28 exists in the shoulder region Zs. The cord 30 does not exist in the shoulder region Zs.

[0037] Figure 1 A first block pair P1, a second block pair P2, a third block pair P3, and a fourth block pair P4 are shown. These block pairs exist in the crown region Zc. The block pairs can also exist in the middle region Zm. The block pairs can also exist in the shoulder region Zs. The attribution of the block pair existing across the boundary of the regions is determined based on the area barycenter of the outline shape of the block pair. The region to which the area barycenter belongs is the region to which the block pair belongs.

[0038] Figure 3 is a perspective view showing the first block pair P1, Figure 4 is a plan view showing the first block pair P1. The first block pair P1 has a left block 28a, a right block 28b, and a cord 30.

[0039] The left block 28a and the right block 28b are adjacent to each other. No other block 28 exists between the left block 28a and the right block 28b. As will be described later, the left block 28a and the right block 28b are mirror-symmetrical with respect to the equatorial plane Eq. Figure 1 As is clear, in the present embodiment, the left block 28a and the right block 28b are mirror-symmetrical with respect to the equatorial plane Eq. Each block 28 has a land 32 and a side 34. The land 32 is flat. The side 34 extends from the land 32 toward the groove 26 (refer to Figure 1 ). In Figure 1 , the illustration of the side 34 is omitted.

[0040] The cord 30 is sandwiched by the left block 28a and the right block 28b. The cord 30 links the left block 28a and the right block 28b. In the present embodiment, the cord 30 exists on the equatorial plane Eq. The cord 30 is recessed from the plane formed by the two lands 32. In other words, the height of the cord 30 is smaller than the height of the block 28.

[0041] In the present invention, a block pair having two blocks 28 and a cord 30 sandwiching the blocks 28 and linking the blocks 28 is referred to as a "linked block pair". The first block pair P1 is a linked block pair. As described above, since the height of the cord 30 is smaller than the height of the block 28, in the linked block pair, the land 32 of the left block 28a and the land 32 of the right block 28b are independent of each other.

[0042] As described above, the reinforcing rib 30 connects the left tread block 28a and the right tread block 28b. Therefore, excessive deformation of the left tread block 28a can be prevented by the reinforcing rib 30 and the right tread block 28b. Similarly, excessive deformation of the right tread block 28b can be prevented by the reinforcing rib 30 and the left tread block 28a. The reinforcing rib 30 contributes to the rigidity of the tread block pair. In the tire 2 with the connecting tread block pair, the tread 4 has high rigidity. When this tire 2 is mounted on the drive wheel, it contributes to traction performance on hard surfaces.

[0043] like Figure 1 As shown, the second patterned block pair P2 has a left patterned block 28a and a right patterned block 28b. The left patterned block 28a and the right patterned block 28b are adjacent to each other. In this embodiment, the left patterned block 28a and the right patterned block 28b are mirror-symmetric with respect to the equatorial plane Eq. The second patterned block pair P2 does not have a tie rod 30. Therefore, a groove 26 exists between the left patterned block 28a and the right patterned block 28b. The second patterned block pair P2 is not a connecting patterned block pair.

[0044] like Figure 1 As shown, the third patterned block pair P3 has a left patterned block 28a, a right patterned block 28b, and a tie rod 30. The left patterned block 28a and the right patterned block 28b are adjacent to each other. In this embodiment, the left patterned block 28a and the right patterned block 28b are mirror-symmetrical with respect to the equatorial plane Eq. In this embodiment, the tie rod 30 exists on the equatorial plane Eq. The tie rod 30 is sandwiched between the left patterned block 28a and the right patterned block 28b. Similar to the tie rod 30 of the first patterned block pair P1, the tie rod 30 of the third patterned block pair P3 connects the left patterned block 28a and the right patterned block 28b. The third patterned block pair P3 is a connecting patterned block pair. The width of the tie rod 30 of the third patterned block pair P3 is greater than the width of the tie rod 30 of the first patterned block pair P1. The specifications of the third patterned block pair P3, except for the width of the tie rod 30, are approximately the same as those of the first patterned block pair P1.

[0045] like Figure 1 As shown, the fourth patterned block pair P4 has a left patterned block 28a, a right patterned block 28b, and a tie rod 30. The left patterned block 28a and the right patterned block 28b are adjacent to each other. In this embodiment, the left patterned block 28a and the right patterned block 28b are mirror symmetrical with respect to the equatorial plane Eq. In this embodiment, the tie rod 30 exists on the equatorial plane Eq. The tie rod 30 is sandwiched between the left patterned block 28a and the right patterned block 28b. Similar to the tie rod 30 of the first patterned block pair P1, the tie rod 30 of the fourth patterned block pair P4 connects the left patterned block 28a and the right patterned block 28b. The fourth patterned block pair P4 is a connecting patterned block pair. The width of the tie rod 30 of the fourth patterned block pair P4 is greater than the width of the tie rod 30 of the first patterned block pair P1. The specifications of the fourth patterned block pair P4, except for the width of the tie rod 30, are roughly the same as those of the first patterned block pair P1.

[0046] Figure 5 is a sectional view taken along the V-V line of Figure 4 . Figure 6 is a sectional view taken along the VI-VI line of Figure 4 . Figure 5 and Figure 6 shows a first block pair P1. Hereinafter, the present application will be described in detail based on the first block pair P1. The following description is also applicable to the joint block pair other than the first block pair P1.

[0047] The rib 30 has a top surface 36 and a side surface 37 (see also Figure 3 and Figure 4 ). The top surface 36 is inclined with respect to the circumferential direction (Y direction). The top surface 36 has a front landing side end 38 and a rear landing side end 40. The side surface 37 is smoothly continuous with the side surface 34 of the block 28.

[0048] In Figure 6 , an arrow Hb indicates the height of the block 28 from the groove 26, an arrow H1 indicates the height of the front landing side end 38 from the groove 26, and an arrow H2 indicates the height of the rear landing side end 40 from the groove 26. The height Hb is the distance of the edge Ed of the rear landing side of the land 32 from the groove 26. The height H2 of the rear landing side end 40 is the same as or smaller than the height Hb of the block 28. The height H1 of the front landing side end 38 is smaller than the height Hb of the block 28 and smaller than the height H2 of the rear landing side end 40.

[0049] Figure 6 Also shown is a road surface G. The road surface G is soft. Therefore, a part of the block 28 penetrates into the road surface G. Figure 6 An arrow A1 in Figure 6 indicates the forward rotation direction of the tire 2. Due to the forward rotation of the tire 2, the vicinity of the front landing side end 38 lands first. The landing position gradually moves along the top surface 36. The direction of this movement is the left direction in .

[0050] During braking, the motorcycle decelerates. When decelerating, the load applied to the tire 2 is low. In addition, when decelerating, the peripheral speed of the tire 2 is smaller than the moving speed of the motorcycle. In Figure 6 , an arrow A2 indicates the direction of the force applied to the joint block pair when decelerating.

[0051] Because the height H1 of the first-touching end 38 is less than the height H2 of the rear-touching end 40, the tire 2 rotates while the reinforcing bar 30 pushes aside the soil and gravel. Therefore, even when a force is applied in the direction of arrow A2, the drag generated by the reinforcing bar 30 is small. The reinforcing bar 30 fully penetrates the road surface G. By penetrating, slippage between the tire 2 and the road surface G is suppressed. The tire 2 exhibits superior grip performance during deceleration (or under low load).

[0052] The fact that the height H1 of the first contact end 38 is less than the height H2 of the rear contact end 40 is a disadvantage for the rib 30 during acceleration. In the front tire (driven wheel), high grip during acceleration is not required. From the viewpoint of low drag, low grip during acceleration is preferable. When the tire 2 of the present invention is mounted on the front rim, both good grip during deceleration and low drag during acceleration can be achieved.

[0053] The rear tire (drive wheel) is subjected to a very large load during acceleration. Therefore, even though the height H1 of the first contact end 38 is less than the height H2 of the rear contact end 40, the reinforcing rib 30 penetrates the road surface G sufficiently. The reinforcing rib 30 does not significantly impair the grip performance during acceleration. When the tire 2 of the present invention is mounted on the rear rim, the reinforcing rib 30 enables good grip performance during deceleration and high rigidity (traction) during acceleration and constant speed driving.

[0054] According to Figure 6 As explicitly stated, in this embodiment, the height of the tie rod 30 gradually increases from the first-landing end 38 towards the rear-landing end 40. In other words, the top surface 36 does not have a stepped difference. The tie rod 30 effectively clears away soil and gravel. The tie rod 30 may also have a stepped difference.

[0055] exist Figure 6 In the attached diagram, reference θ indicates the angle of the line connecting the first-landing end 38 and the second-landing end 40 relative to the circumferential direction (Y direction). Angle θ is preferably 2° or more. A tie rod 30 with an angle θ of 2° or more effectively removes soil and gravel. From this perspective, an angle θ of 10° or more is more preferable, and particularly preferably 20° or more. A tie rod 30 with an excessively large angle θ actually increases drag during deceleration. From the viewpoint of low drag, an angle θ is preferably 55° or less, more preferably 50° or less, and particularly preferably 45° or less. When the tie rod 30 has a stepped difference, the line connecting the first-landing end 38 and the second-landing end 40 also serves as a reference for determining the angle θ.

[0056] The difference (H2-H1) between the height H2 of the rear-landing-side end 40 and the height H1 of the front-landing-side end 38 is preferably 0.5 mm or more and 10.0 mm or less. The bar 30 having the difference (H2-H1) within the above range sufficiently digs up earth and gravel. From this viewpoint, the difference (H2-H1) is more preferably 1.5 mm or more, and particularly preferably 2.0 mm or more. The difference (H2-H1) is more preferably 8.0 mm or less, and particularly preferably 7.0 mm or less. The height H1 is preferably 0.0 mm or more and 15.0 mm or less. The height H2 is preferably 0.5 mm or more and 20.0 mm or less.

[0057] The ratio H2 / Hb of the height H2 of the rear-landing-side end 40 to the height Hb of the block 28 is preferably 0.20 or more and 0.95 or less. The linked block pair having the ratio H2 / Hb of 0.20 or more can have sufficient rigidity. From this viewpoint, the ratio H2 / Hb is more preferably 0.35 or more, and particularly preferably 0.50 or more. In the linked block pair having the ratio H2 / Hb of 0.95 or less, the left block 28a and the right block 28b respectively sufficiently penetrate into the road surface. From this viewpoint, the ratio H2 / Hb is more preferably 0.80 or less, and particularly preferably 0.70 or less.

[0058] In Figure 5 In the formula, the reference symbol Wb denotes the width of the linked block pair, and Wt denotes the width of the bar 30. The width Wb and the width Wt are measured along the axial direction (X direction). From the viewpoint of the penetration of the left block 28a and the right block 28b into the road surface and the viewpoint of the rigidity of the linked block pair, the ratio Wt / Wb of the width Wt to the width Wb is preferably 0.05 or more and 0.50 or less.

[0059] The tread 4 can have the linked block pair in which the height of the rear-landing-side end 40 is greater than the height of the front-landing-side end 38, in addition to the linked block pair in which the height of the rear-landing-side end 40 is equal to the height of the front-landing-side end 38. The tread 4 can have the linked block pair in which the height of the rear-landing-side end 40 is less than the height of the front-landing-side end 38. Preferably, the tire 2 satisfies the following formula.

[0060] N1 / N ≥ 0.10

[0061] N = N1 + N2 + N3 + N4

[0062] N1: the number of the linked block pair in which the height of the rear-landing-side end 40 is greater than the height of the front-landing-side end 38 in the crown region Zc

[0063] N2: the number of the linked block pair in which the height of the rear-landing-side end 40 is equal to the height of the front-landing-side end 38 in the crown region Zc

[0064] N3: Number of the linked block pairs in which the height of the rear landing side end 40 in the crown region Zc is smaller than the height of the front landing side end 38

[0065] N4: Number of the block pairs in the crown region Zc which are not the linked block pairs

[0066] In other words, the ratio N1 / N of the number N1 of the linked block pairs in which the height of the rear landing side end 40 in the crown region Zc is greater than the height of the front landing side end 38 with respect to the total number N of the block pairs is 0.10 or more. The tire 2 in which the ratio N1 / N is 0.10 or more is superior in the grip performance at the time of deceleration (or at the time of low load). From this viewpoint, the ratio (N1 / N) is more preferably 0.25 or more, and particularly preferably 0.50 or more. The ratio N1 / N can also be 1.00.

[0067] The land ratio in the block pattern is preferably 13% or more and 60% or less. In the tire 2 in which the land ratio is 13% or more, the ground pressure can be dispersed. In the tire 2, the damage to the block 28 can be suppressed. From this viewpoint, the land ratio is more preferably 14% or more, and particularly preferably 15% or more. In the tire 2 in which the land ratio is 60% or less, each block 28 sufficiently penetrates into the road surface at the time of traveling on a soft road surface. From this viewpoint, the land ratio is more preferably 50% or less, and particularly preferably 40% or less.

[0068] The land ratio is the ratio of the total area of all lands 32 with respect to the area of the imaginary tread surface. The imaginary tread surface refers to the tread surface in which the grooves 26, the ribs 30, the side faces 34, and the side faces 37 are assumed to be not present and all are lands 32.

[0069] The hardness of the linked block pair is preferably 45 or more and 88 or less. The linked block pair having the hardness in this range can contribute to the grip performance in a hard road surface. From this viewpoint, the hardness is more preferably 55 or more, and particularly preferably 60 or more. From this viewpoint, the hardness is more preferably 80 or less, and particularly preferably 75 or less. The hardness is measured by pressing a JIS-A type hardness tester against the linked block pair. The temperature at the time of measurement is 25°C.

[0070] In this invention, the dimensions and angles of each component of tire 2 are measured with tire 2 assembled on a standard rim and filled with air to a standard internal pressure. No load is applied to tire 2 during measurement. In this specification, a standard rim means the rim specified in the specification upon which tire 2 is based. "Standard rim" in JATMA specifications, "Design Rim" in TRA specifications, and "Measuring Rim" in ETRTO specifications are standard rims. In this specification, standard internal pressure means the internal pressure determined in the specification upon which tire 2 is based. "Maximum air pressure" in JATMA specifications, "maximum value" as stated in "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES" in TRA specifications, and "INFLATION PRESSURE" in ETRTO specifications are standard internal pressures.

[0071]

Example

[0072] The effects of the present invention are illustrated below through examples, but the present invention should not be interpreted in a limiting way based on the description of these examples.

[0073] [Experiment 1 Front Tire]

[0074] [Example 1]

[0075] Obtain with Figure 1 The front tire shown in Figure 6 has a size of "80 / 100-21". The tire's crown area has multiple tread block pairs. The ratio N1 of the number of connecting tread block pairs in the crown area where the height of the rear contact side is greater than the height of the front contact side to the total number of tread block pairs N is 0.75. In each connecting tread block pair, the height H1 of the front contact side is 2.0 mm, and the height H2 of the rear contact side is 8.0 mm.

[0076] [Examples 2-7 and Comparative Examples 1-2]

[0077] Except that the heights H1 and H2 are set as shown in Tables 1 and 2 below, tires of Examples 2-7 and Comparative Examples 1-2 are obtained in the same manner as in Example 1.

[0078] [Examples 8-10]

[0079] Except that the ratio N1 / N is set as shown in Table 3 below, tires of Examples 8-10 are obtained in the same manner as in Example 1.

[0080] [Sensory Evaluation]

[0081] Inflate the tires with air and set the internal pressure to 80 kPa.a The tire was mounted on a front rim (WM 1.60) of a commercially available motorcycle for rough road travel (engine: 4-cycle type, displacement: 450 cc ). A commercially available tire was mounted on a rear rim. The motorcycle was made to run on a motocross course having a hard road surface and a soft road surface, and the grip performance at deceleration and the low resistance at acceleration were evaluated by a rider. The results are shown as indices in Tables 1-3 below. The larger the value, the better the performance.

[0082] [Overall Evaluation]

[0083] Each tire was classified into a grade based on the following criteria.

[0084] A: The value of the grip performance at deceleration was 110 or more, and the low resistance at acceleration was superior to that of Comparative Example 1.

[0085] B: The value of the grip performance at deceleration was 101 or more but less than 110, and the low resistance at acceleration was superior to that of Comparative Example 1.

[0086] C: The value of the grip performance at deceleration was 100 or less.

[0087] The results are shown in Tables 1-3 below.

[0088] [Table 1]

[0089] Table 1: Evaluation Results of Front Tires

[0090]

[0091] [Table 2]

[0092] Table 2: Evaluation Results of Front Tires

[0093]

[0094] [Table 3]

[0095] Table 3: Evaluation Results of Front Tires

[0096]

[0097] As shown in Tables 1-3, the overall evaluation grade of the tire of each example was A or B. From the evaluation results, the superiority of the present application was made clear.

[0098] [Experiment 2 Rear Tire]

[0099] [Example 1]

[0100] A tire having the same construction as Figure 1The illustrated pattern is the same as the block pattern of the rear tire. The size of this tire is "120 / 90-19". The crown region of this tire has a plurality of block pairs. The ratio N1 / N of the number N1 of the number of block pairs in the crown region in which the height of the rear landing side end is greater than that of the front landing side end to the total number N of block pairs is 0.75. In each of the block pairs, the height H1 of the front landing side end is 3.0 mm, and the height H2 of the rear landing side end is 9.0 mm.

[0101] [Examples 2-7 and Comparative Examples 1-2]

[0102] The tires of Examples 2-7 and Comparative Examples 1-2 were obtained in the same manner as in Example 1, except that the height H1 and the height H2 were set as shown in Tables 4 and 5 below.

[0103] [Examples 8-10]

[0104] The tires of Examples 8-10 were obtained in the same manner as in Example 1, except that the ratio N1 / N was set as shown in Table 6 below.

[0105] [Perceptual Evaluation]

[0106] The tire was filled with air, and the internal pressure was set to 80 kPa. a The tire was mounted on the rear rim (WM 2.15) of a commercially available uneven ground running motorcycle (engine: 4-stroke type, displacement: 450 cc A commercially available tire was mounted on the front rim. The motorcycle was made to run on a motocross course having a hard road surface and a soft road surface, and the rider evaluated the grip performance at deceleration and the traction at acceleration and constant speed running. The results are shown as indices in Tables 4-6 below. The larger the value, the better the performance.

[0107] [Overall Evaluation]

[0108] Each tire was classified into a grade based on the following criteria.

[0109] A: The value of the grip performance at deceleration was 110 or more, and the resistance at acceleration was 95 or more.

[0110] B: The value of the grip performance at deceleration was 101 or more and less than 110, and the resistance at acceleration was 95 or more.

[0111] C: The value of the grip performance at deceleration was 100 or less.

[0112] The results are shown in Tables 4-6 below.

[0113]

Table 4

[0114] Table 4: Evaluation Results of Rear Tire

[0115]

[0116] Table 5

[0117] Table 5: Evaluation results of rear tires

[0118]

[0119] Table 6

[0120] Table 6: Evaluation results of rear tires

[0121]

[0122] As shown in Tables 4 to 6, the overall evaluation of the tires of each example was A or B. From the evaluation results, the superiority of the present application was made clear.

[0123]

Industrial applicability

[0124] The tire according to the present application can be mounted to a motorcycle that runs on various road surfaces.

Claims

1. A motorcycle tire for rough terrain, characterized by comprising a tread having block patterns, the block pattern has a groove, a plurality of blocks each standing from the groove and having a land and a side surface extending from the land toward the groove, and a plurality of ribs each standing from the groove, a pair of blocks having two blocks each adjacent to each other in the axial direction is formed in the block pattern, the pairs of blocks include a plurality of linked pairs of blocks, each linked pair of blocks has two blocks and a rib sandwiched by and linking the two blocks, in the linked pair of blocks, the rib has a top surface having a rear landing side end having a height equal to or smaller than that of the blocks and a front landing side end having a height smaller than that of the rear landing side end, a side surface of the rib is connected to the rear landing side end and the front landing side end of the top surface, respectively, and the side surface of the rib is smoothly continuous with the side surface of the blocks, the rib has a height gradually increasing toward the rear landing side end from the front landing side end, a ratio H2 / Hb of a height H2 of the rear landing side end to a height Hb of the blocks in the linked pair of blocks is 0.50 or more and 0.95 or less, the tire is mounted on a front wheel rim of a motorcycle, an angle of a line connecting the front landing side end and the rear landing side end with respect to the circumferential direction is 19° or more.

2. The tire according to claim 1, characterized in that, the tread has a crown region located in the axial center, a pair of intermediate regions each located on an axial outer side of the crown region, and a pair of shoulder regions each located on an axial outer side of the intermediate region, a ratio N1 / N of a number N1 of linked pairs of blocks in which the height of the rear landing side end is greater than that of the front landing side end to a number N of pairs of blocks in the crown region is 0.10 or more.

3. The tire according to claim 1 or 2, characterized in that, a land ratio of the block pattern is 13% or more and 60% or less.

4. The tire according to claim 1 or 2, characterized in that, a JIS-A hardness of the linked pair of blocks is 45 or more and 88 or less. ​

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