Tire

Abstract

To provide a tire (2) excellent in wet grip performance, dry grip performance, and wear resistance. The tire has a tread with a first circumferential groove located at a position on a shoulder side from an equatorial plane of the tire, a second circumferential groove located at a position on a back side from the equatorial plane, and a third circumferential groove located at a position on the back side from the second circumferential groove. The first circumferential groove has a main section having a shoulder side wall and a back side wall, and a sub section reaching a tread surface from the shoulder side wall, and an inclination angle θ1s thereof is larger than an inclination angle θ1f of the shoulder side wall. A width W1m of the main section is smaller than a width W2 of the second circumferential groove and smaller than a width W3 of the third circumferential groove.

Description

TECHNICAL FIELD

[0001] The present application relates to a tire. In detail, the present application relates to improvement of a tread pattern of a tire. BACKGROUND

[0002] A tread of a general tire has a circumferential groove and an inclined groove. The circumferential groove mainly discharges water between the tire and a road surface in a front-rear direction. The inclined groove mainly discharges the water in a lateral direction. These grooves contribute to wet road grip performance of the tire.

[0003] In Japanese Patent Application Publication No. 2018-167717, a tire having three circumferential grooves is described. One circumferential groove is located on a land side with respect to an equatorial plane. Two circumferential grooves are located on a back side with respect to the equatorial plane. In other words, a tread pattern of the tire is asymmetric with respect to the equatorial plane. The tread pattern can contribute to wet road grip performance and dry road grip performance.

[0004] Patent Literature 1: Japanese Patent Application Publication No. 2018-167717 SUMMARY

[0005] There is room for improvement in the grip performance of the existing tire. Further, there is room for improvement in the wear resistance of the existing tire. An object of the present application is to provide a tire excellent in wet road grip performance, dry road grip performance, and wear resistance.

[0006] The tire according to the present application has a tread having a tread surface. The tread has:

[0007] a first circumferential groove located on a land side with respect to an equatorial plane of the tire;

[0008] a second circumferential groove located on a back side with respect to the equatorial plane; and

[0009] a third circumferential groove located on the back side with respect to the second circumferential groove.

[0010] The first circumferential groove has:

[0011] a main section having a land side wall and a back side wall; and

[0012] a sub-section reaching the tread surface from the land side wall, and an inclination angle θ1s of the sub-section is larger than an inclination angle θ1f of the land side wall.

[0013] A width W1m of the main section is smaller than a width W2 of the second circumferential groove and smaller than a width W3 of the third circumferential groove.

[0014] It is preferable that a ratio of the width W1m of the main section with respect to a width Tw of the tread surface is 1.0% or more and 5.0% or less.

[0015] The inclination angle θ1f of the surface-side wall is preferably 0° or more and 45° or less. The inclination angle θ1s of the sub-portion is preferably 40° or more and 80° or less.

[0016] The width W1s (mm) of the sub-portion preferably satisfies the following mathematical expression:

[0017] 1.0*cosθ1f≤W1s≤5.0*cosθ1f.

[0018] The second circumferential groove can have a surface-side wall and a back-side wall. The ratio of the inclination angle θ2b (degree) of the back-side wall with respect to the width Tw (mm) of the tread surface is preferably 5% or more and 20% or less. The ratio of the inclination angle θ2f of the surface-side wall with respect to the inclination angle θ2b of the back-side wall is preferably 60% or more and 90% or less.

[0019] The third circumferential groove can have a surface-side wall and a back-side wall. The ratio of the inclination angle θ3b (degree) of the back-side wall with respect to the width Tw (mm) of the tread surface is preferably 5% or more and 20% or less. The ratio of the inclination angle θ3f of the surface-side wall with respect to the inclination angle θ3b of the back-side wall is preferably 60% or more and 90% or less.

[0020] The tire preferably further has:

[0021] a surface-side triangular groove extending from the second circumferential groove toward the back-side and having a circumferential dimension that gradually decreases as it approaches the back-side and a depth that gradually decreases as it approaches the back-side; and

[0022] a back-side triangular groove extending from the third circumferential groove toward the surface-side and having a circumferential dimension that gradually decreases as it approaches the surface-side and a depth that gradually decreases as it approaches the surface-side.

[0023] The ratio of the width Wtf of the surface-side triangular groove with respect to the width Wr of the rib sandwiched by the second circumferential groove and the third circumferential groove is preferably 0.10 or more and 0.30 or less. The ratio of the width Wtb of the back-side triangular groove with respect to the width Wr of the rib is preferably 0.10 or more and 0.30 or less.

[0024] The inclination angle θtf of the bottom of the surface-side triangular groove is preferably 40° or more and 70° or less. The inclination angle θtb of the bottom of the back-side triangular groove is preferably 40° or more and 70° or less.

[0025] The tire preferably further has a sipe that links the surface-side triangular groove and the back-side triangular groove. The depth Dp of the sipe is preferably 2.0 mm or more.

[0026] In the pneumatic tire according to the present application, the plurality of circumferential grooves contribute to wet road grip performance. These circumferential grooves do not substantially hinder the rigidity of the tread. Therefore, the dry road grip performance of the tire is excellent. These circumferential grooves do not contribute to uneven wear of the tread. The wear resistance of the tire is also excellent. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a front view showing a tire according to an embodiment of the present application together with a vehicle.

[0028] Figure 2 is an enlarged sectional view showing a portion of the tire of Figure 1 .

[0029] Figure 3 is an expanded view showing a portion of the tread pattern of the tire of Figure 1 .

[0030] Figure 4 is an enlarged sectional view taken along the line IV-IV of Figure 3 .

[0031] Figure 5 is an enlarged sectional view taken along the line V-V of Figure 3 .

[0032] Figure 6 is an enlarged sectional view taken along the line VI-VI of Figure 3 .

[0033] Figure 7 is an enlarged sectional view taken along the line VII-VII of Figure 3 .

[0034] EXPLANATION OF REFERENCE NUMERALS

[0035] 2...tire; 4...vehicle; 6...vehicle body; 8...axle; 10...tread; 24...tread surface; 34...first circumferential groove; 36...second circumferential groove; 38...third circumferential groove; 40...first rib; 42...second rib; 44...third rib; 46...fourth rib; 62...main section; 64...sub section; 68...floor surface of first circumferential groove; 70...surface side wall of first circumferential groove; 72...back side wall of first circumferential groove; 78...floor surface of second circumferential groove; 80...surface side wall of second circumferential groove; 82...back side wall of second circumferential groove; 88...floor surface of third circumferential groove; 90...surface side wall of third circumferential groove; 92...back side wall of third circumferential groove; 98...surface side triangular groove; 100...back side triangular groove; 102...sipe. DETAILED DESCRIPTION

[0036] Hereinafter, the present application will be described in detail based on preferred embodiments with appropriate reference to the accompanying drawings.

[0037] Hereinafter, the present application will be described in detail based on preferred embodiments with appropriate reference to the accompanying drawings.Figure 1 In the diagram, tire 2 is shown together with vehicle 4. Vehicle 4 has a body 6 and an axle 8. Tire 2 is connected to axle 8 via wheels and rims (not shown). Figure 1 The left side of the image is the face side of tire 2. This face side is also the outer side of vehicle 4 in the width direction. Figure 1 The right side of the image is the back side of tire 2. This back side is also the inside side of vehicle 4 in the width direction.

[0038] Figure 2 In, it is shown that along the containing Figure 1 A portion of the cross-section of tire 2 is cut along a plane including the axis of rotation of tire 2. Figure 2 In the diagram, the vertical direction represents the radius of tire 2, the horizontal direction represents the axial direction of tire 2, and the direction perpendicular to the plane of the paper represents the circumferential direction of tire 2. Figure 2 In the diagram, the dotted line CL represents the equatorial plane of tire 2. Except for the tread pattern described later, the shape of tire 2 is mirror symmetrical with respect to the equatorial plane CL. The dotted line CL is also the centerline of tire 2 in the axial direction.

[0039] The tire 2 has a tread 10, a pair of sidewalls 12, a pair of bead 14, a carcass 16, a belt 18, a belt 20, and an inner liner 22. The tire 2 can have various other components. The tire 2 is tubeless. The tire 2 is typically mounted on a four-wheeled vehicle.

[0040] The tread 10 is shaped to project radially outward. The tread 10 forms a tread surface 24 that contacts the road surface. The tread 10 is made of a cross-linked rubber composition. The tread 10 may also have a base and a top covering the base. The tread 10 may also have three or more layers. The tread 10 has multiple grooves 34, 36, and 38. Tread patterns are formed through these grooves 34, 36, and 38. The structure of the tread pattern is described in detail below.

[0041] Each sidewall 12 extends from the tread 10 in a generally radially inward direction. A portion of the sidewall 12 engages with the tread 10. The sidewall 12 is made of cross-linked rubber with excellent cut resistance and weather resistance. The sidewall 12 prevents damage to the tire carcass 16.

[0042] Each bead 14 is located axially inward of the sidewall 12. Each bead 14 has a bead core 26 and a triangular rubber 28 extending radially outward from the bead core 26. The bead core 26 is annular and contains a wound, non-stretchable thread. The thread is typically made of steel. The triangular rubber 28 tapers radially outward. The triangular rubber 28 is made of a high-hardness cross-linked rubber.

[0043] The carcass 16 is positioned between the two bead 14s and extends along the tread 10 and sidewall 12. The carcass 16 has multiple parallel cords and adhesive strips. The absolute value of the angle formed by each cord relative to the equatorial plane CL is 75° to 90°. In other words, the carcass 16 has a radial configuration. The cords are made of organic fibers. Examples of preferred organic fibers include polyester fibers, nylon fibers, synthetic fibers, polyethylene naphthalate fibers, and aramid fibers.

[0044] The belt 18 is located radially inside the tread 10. The belt 18 is stacked with the carcass 16. The belt 18 reinforces the carcass 16. The belt 18 has an inner layer 30 and an outer layer 32. The inner layer 30 and the outer layer 32 each have a plurality of parallel cords and adhesive. Each cord is inclined relative to the equatorial plane CL. The absolute value of the inclination angle is typically greater than 10° and less than 35°. The inclination direction of the cords of the inner layer 30 relative to the equatorial plane CL is opposite to the inclination direction of the cords of the outer layer 32 relative to the equatorial plane CL. The preferred material for the cords is steel. Organic fibers can also be used for the cords. Examples of organic fibers include polyester fibers, nylon fibers, synthetic fibers, polyethylene naphthalate fibers, and aramid fibers.

[0045] The belt 20 is located radially outside the belt bundle 18. The belt 20 has cords and adhesive. The cords are wound in a spiral shape. The belt 20 has a so-called seamless construction. The cords extend virtually circumferentially. The angle of the cords relative to the circumferential direction is less than 5°, and further less than 2°. The cords are made of organic fibers. Examples of preferred organic fibers include nylon fibers, polyester fibers, synthetic fibers, polyethylene naphthalate fibers, and aramid fibers.

[0046] Figure 3 It shows Figure 1 A partial unfolded diagram of the tread pattern of tire 2. Figure 3 In the center, the vertical direction is the circumferential direction. The vertical direction is also the direction of travel of tire 2 (in other words, the front). Figure 3 In the center, the left side is the surface side and the right side is the back side. This tread pattern has a first circumferential groove 34, a second circumferential groove 36, and a third circumferential groove 38. These circumferential grooves divide the tread surface 24 into four ribs. Specifically, the tread surface 24 has a first rib 40, a second rib 42, a third rib 44, and a fourth rib 46. The first rib 40 is located on the surface side of the first circumferential groove 34. The second rib 42 is sandwiched between the first circumferential groove 34 and the second circumferential groove 36. The third rib 44 is sandwiched between the second circumferential groove 36 and the third circumferential groove 38. The fourth rib 46 is located on the back side of the third circumferential groove 38. Figure 3 In the figure, the reference numeral Tw indicates the width of the tread 10, and the reference numeral Wr indicates the width of the third rib 44. Widths Tw and Wr are measured along the axial direction.

[0047] The tread pattern has a plurality of first lateral grooves 48 respectively located at positions closer to the surface side than the first circumferential groove 34. The tread pattern has a plurality of second lateral grooves 50 respectively extending from the first circumferential groove 34 toward the surface side, and a plurality of third lateral grooves 52 respectively extending from the first circumferential groove 34 toward the back side. The tread pattern has a plurality of fourth lateral grooves 54 respectively extending from the second circumferential groove 36 toward the surface side. The tread pattern has a plurality of fifth lateral grooves 56 respectively extending from the third circumferential groove 38 toward the back side. The tread pattern has a plurality of sixth lateral grooves 58 respectively located at positions closer to the back side than the third circumferential groove 38.

[0048] In the tread pattern, Figure 3 The pattern of the unit 60 shown is repeated in the circumferential direction. Therefore, the pitch of the lateral grooves is constant. The tread pattern can also have a variation in the pitch of the lateral grooves.

[0049] The first circumferential groove 34 extends in the circumferential direction. Therefore, the first circumferential groove 34 is annular. The first circumferential groove 34 is located at a position closer to the surface side than the equatorial plane CL. In the tread pattern, the number of circumferential grooves located at a position closer to the surface side than the equatorial plane CL is 1.

[0050] Figure 4 is an enlarged sectional view taken along the IV-IV line of Figure 3 Figure 4 In Fig. 2, the vicinity of the first circumferential groove 34 is shown. Figure 4 In Fig. 2, the up-down direction is the normal direction of the tread surface 24. In Figure 4 In Fig. 2, the left side is the surface side, and the right side is the back side. The first circumferential groove 34 has a main section 62 and a sub-section 64. In Figure 4 In Fig. 2, reference numeral 66 denotes the boundary between the main section 62 and the sub-section 64. The sub-section 64 is located at a position closer to the surface side (left side of Fig. 2) than the main section 62. Figure 4 The main section 62 has a floor surface 68, a surface side wall 70, and a back side wall 72.

[0051] The surface side wall 70 is located at a position closer to the surface side than the floor surface 68. The surface side wall 70 rises from the floor surface 68. The surface side wall 70 is inclined with respect to the normal direction. The direction of the inclination is a direction that tends toward the surface side as it moves away from the floor surface 68. In Figure 4 In Fig. 2, reference numeral θ1f denotes the degree of inclination of the surface side wall 70 with respect to the normal direction.

[0052] The back side wall 72 is located at a position closer to the back side than the floor surface 68. The back side wall 72 rises from the floor surface 68. The back side wall 72 is inclined with respect to the normal direction. The direction of the inclination is a direction that tends toward the back side as it moves away from the floor surface 68. In Figure 4 ​In the accompanying drawings, reference numeral θ1b indicates the angle of inclination (degree) of the back sidewall 72 relative to the normal direction. In this embodiment, the angle of inclination θ1b ​​is the same as the angle of inclination θ1f. The first circumferential groove 34 may also have a main segment 62 with different angles of inclination θ1b ​​and inclination θ1f.

[0053] exist Figure 4 In the attached figure, the reference numeral W1m indicates the width (mm) of the main segment 62. The width W1m is the distance between the normal at the boundary 66 and the normal at the edge 74 of the back sidewall 72.

[0054] Sub-segment 64 extends from the outer sidewall 70 to the tread surface 24. Sub-segment 64 is inclined relative to the normal direction. This inclination direction tends towards the outer side as it moves away from the boundary 66. Figure 4 In the attached diagram, the reference numeral θ1s indicates the tilt angle (degree) of sub-segment 64 relative to the normal direction. The tilt angle θ1s is greater than the tilt angle θ1f of the sidewall 70.

[0055] exist Figure 4 In the attached figure, the reference numeral W1s indicates the width (mm) of sub-segment 64. The width W1s is the distance between the normal at boundary 66 and the normal at edge 76 of sub-segment 64.

[0056] like Figure 3 As shown, the second circumferential groove 36 extends circumferentially. Therefore, the second circumferential groove 36 is annular. The second circumferential groove 36 is located on the back side of the equatorial plane CL. In this embodiment, the second circumferential groove 36 is separate from the equatorial plane CL. The second circumferential groove 36 may also span the equatorial plane CL. In this case, the axial center of the second circumferential groove 36 is located on the back side of the equatorial plane CL. In other words, in this invention, the axial center of the groove is used as a reference to determine the region to which the groove belongs.

[0057] Figure 5 It is along Figure 3 An enlarged sectional view of the VV line section. Figure 5 The image shows the vicinity of the second circumferential ditch 36. Figure 5 The vertical direction is the normal direction of the tread surface 24. Figure 5 In the middle, the left side is the surface side and the right side is the back side. The second circumferential trench 36 has a bottom surface 78, a surface sidewall 80, and a back sidewall 82.

[0058] The surface sidewall 80 is located closer to the surface than the bottom surface 78. The surface sidewall 80 rises from the bottom surface 78. The surface sidewall 80 is inclined relative to the normal direction. This inclination direction tends towards the surface as it moves away from the bottom surface 78. Figure 5 In the attached figure, the reference θ2f indicates the angle (degree) of inclination of the sidewall 80 relative to the normal direction.

[0059] The back side wall 82 is located at a position closer to the back side than the bottom surface 78. The back side wall 82 rises from the bottom surface 78. The back side wall 82 is inclined with respect to the normal direction. The direction of the inclination is a direction that tends toward the back side as it moves away from the bottom surface 78. In Figure 5 In the present embodiment, the reference sign θ2b denotes the degree of inclination of the back side wall 82 with respect to the normal direction. In the present embodiment, the inclination angle θ2b is larger than the inclination angle θ2f. The tire 2 can also have a second circumferential groove 36 in which the inclination angle θ2b is the same as the inclination angle θ2f. The tire 2 can also have a second circumferential groove 36 in which the inclination angle θ2b is smaller than the inclination angle θ2f.

[0060] In Figure 5 In the present embodiment, the reference sign W2 denotes the width (mm) of the second circumferential groove 36. The width W2 is the distance between the normal at the edge 84 of the land side wall 80 and the normal at the edge 86 of the back side wall 82.

[0061] As Figure 3 shown, the third circumferential groove 38 extends in the circumferential direction. Thus, the third circumferential groove 38 is annular. The third circumferential groove 38 is located at a position closer to the back side than the equatorial plane CL. The third circumferential groove 38 is located at a position closer to the back side than the second circumferential groove 36. In this tread pattern, the number of circumferential grooves located at a position closer to the back side than the equatorial plane CL is two.

[0062] Figure 6 is an enlarged cross-sectional view taken along the VI-VI line of Figure 3 Figure 6 In Figure 6 the upward and downward directions in Figure 6 In the present embodiment, the left side is the land side, and the right side is the back side. This third circumferential groove 38 has a bottom surface 88, a land side wall 90, and a back side wall 92.

[0063] The land side wall 90 is located at a position closer to the land side than the bottom surface 88. The land side wall 90 rises from the bottom surface 88. The land side wall 90 is inclined with respect to the normal direction. The direction of the inclination is a direction that tends toward the land side as it moves away from the bottom surface 88. In Figure 6 In the present embodiment, the reference sign θ3f denotes the degree of inclination of the land side wall 90 with respect to the normal direction.

[0064] The back side wall 92 is located at a position closer to the back side than the bottom surface 88. The back side wall 92 rises from the bottom surface 88. The back side wall 92 is inclined with respect to the normal direction. The direction of the inclination is a direction that tends toward the back side as it moves away from the bottom surface 88. In Figure 6 ​In the present embodiment, reference sign θ3b denotes a degree of inclination of the back side wall 92 with respect to the normal direction. In the present embodiment, the degree of inclination θ3b is larger than the degree of inclination θ3f. The tire 2 can also have the third circumferential groove 38 with the same degree of inclination θ3b as the degree of inclination θ3f. The tire 2 can also have the third circumferential groove 38 with the degree of inclination θ3b smaller than the degree of inclination θ3f.

[0065] In Figure 6 In the present embodiment, reference sign W3 denotes a width (mm) of the third circumferential groove 38. The width W3 is a distance between a normal line at the edge 94 of the table side wall 90 and a normal line at the edge 96 of the back side wall 92.

[0066] As Figure 3 shown, the tread pattern has a plurality of table side triangular grooves 98, a plurality of back side triangular grooves 100, and a plurality of sipes 102. These table side triangular grooves 98, back side triangular grooves 100, and sipes 102 are located at positions more back side than the equatorial plane CL.

[0067] Each table side triangular groove 98 is continuous with the second circumferential groove 36. The table side triangular groove 98 extends toward the back side from the second circumferential groove 36. The table side triangular groove 98 has a circumferential dimension that gradually decreases as it tends toward the back side. The profile of the table side triangular groove 98 as viewed from the normal direction of the tread surface 24 is substantially triangular. In the present embodiment, the profile shape of the table side triangular groove 98 is the same as the profile shape of the second circumferential groove 36. In the present embodiment, the number of table side triangular grooves 98 is the same as the number of second circumferential grooves 36. Figure 3 In the present embodiment, reference sign Wtf denotes a width (mm) of the table side triangular groove 98. The width Wtf is measured in a direction perpendicular to the normal of the tread surface 24.

[0068] Each back side triangular groove 100 is continuous with the third circumferential groove 38. The back side triangular groove 100 extends toward the table side from the third circumferential groove 38. The back side triangular groove 100 has a circumferential dimension that gradually decreases as it tends toward the table side. The profile of the back side triangular groove 100 as viewed from the normal direction of the tread surface 24 is substantially triangular. In the present embodiment, the profile shape of the back side triangular groove 100 is the same as the profile shape of the table side triangular groove 98. In the present embodiment, the number of back side triangular grooves 100 is the same as the number of table side triangular grooves 98. Figure 3 In the present embodiment, reference sign Wtb denotes a width (mm) of the back side triangular groove 100. The width Wtb is measured in a direction perpendicular to the normal of the tread surface 24.

[0069] Each of the sipes 102 links the top side sipe 98 and the back side sipe 100. Through the sipe 102, a pair of the top side sipe 98 and the back side sipe 100 is formed. In the present embodiment, the sipe 102 is inclined with respect to the axial direction. Specifically, the sipe 102 extends in a direction toward the front side as it tends toward the back side. In the present embodiment, the number of the sipes 102 is identical to the number of the top side sipes 98, and is also identical to the number of the back side sipes 100. Through the plurality of sipes 102, the third rib 44 is divided into a plurality of units 104.

[0070] Figure 7 is an enlarged sectional view taken along the line VII-VII of Figure 3 . The direction of the line VII-VII is generally identical to the extending direction of the sipe 102. Figure 7 In FIG. 6, the second circumferential groove 36, the top side sipe 98, the sipe 102, the back side sipe 100, and the third circumferential groove 38 are shown.

[0071] The bottom 104 of the top side sipe 98 is inclined with respect to the normal direction. The bottom 104 extends in a direction toward the tread surface 24 as it tends toward the back side. In other words, the top side sipe 98 has a depth that gradually decreases as it tends toward the back side. In Figure 7 In FIG. 6, the reference sign θtf denotes an inclination degree of the bottom 104 of the top side sipe 98 with respect to the normal direction.

[0072] The bottom 106 of the back side sipe 100 is inclined with respect to the normal direction. The bottom 106 extends in a direction toward the tread surface 24 as it tends toward the top side. In other words, the back side sipe 100 has a depth that gradually decreases as it tends toward the top side. In Figure 7 In FIG. 6, the reference sign θtb denotes an inclination degree of the bottom 106 of the back side sipe 100 with respect to the normal direction. In the present embodiment, the inclination degree θtb is identical to the inclination degree θtf. The tire 2 can also have the tread 10 in which the inclination degree θtb is different from the inclination degree θtf.

[0073] In Figure 7 , the reference sign Dp denotes a depth (mm) of the sipe 102. The depth is small. Further, according to Figure 3 , it is known that the width of the sipe 102 is extremely small. Therefore, the distance between the one piece of the tread rubber and the other piece of the tread rubber that face each other across the sipe 102 is extremely small. The one piece of the tread rubber can also abut against the other piece of the tread rubber. Since the sipe 102 has the small depth Dp and the small width, the sipe 102 does not substantially hinder the rigidity of the third rib 44.

[0074] The tire 2 can also have a tread pattern that does not include the sipe 102. The tire 2 can also have a tread pattern that does not include the top side sipe 98 and the back side sipe 100.

[0075] In the tread surface 24, the width WIm (refer to Fig. 2) of the main section 62 is smaller than the width W2 (refer to Fig. 2) of the second circumferential groove 36, and is smaller than the width W3 (refer to Fig. 2) of the third circumferential groove 38. At the position of the tread surface 24 on the back side from the equatorial plane CL, there are two circumferential grooves of which the widths are large. When the tire 2 runs on a wet road surface, water between the road surface and the tread surface 24 is effectively drained through the second circumferential groove 36 and the third circumferential groove 38. The second circumferential groove 36 and the third circumferential groove 38 can contribute to the wet road grip performance of the tire 2. Figure 4 Figure 5 The number of the circumferential grooves existing at the position of the tread surface 24 on the surface side from the equatorial plane CL is only one. Also, the width WIm of the main section 62 of the circumferential groove is small. Further, the sub-section 64 is shallow. Therefore, the rigidity of the tread 10 on the surface side from the equatorial plane CL is large. When the vehicle 4 turns, the portion of the tread 10 on the surface side from the equatorial plane CL is subjected to a large ground pressure. Even if subjected to the ground pressure, excessive deformation of the tread 10 does not occur. The dry road grip performance and the wear resistance of the tire 2 are excellent. Figure 6

[0076] Since the first circumferential groove 34 has the sub-section 64, the invasion of the rubber into the main section 62 caused by the elastic deformation of the first rib 40 is prevented by the sub-section 64. Therefore, the cross-sectional area of the main section 62 in the state where the ground pressure is applied is sufficiently large. In the tire 2, the drainability of the main section 62 is not hindered even if the ground pressure is applied. The wet road grip performance of the tire 2 is extremely excellent.

[0077] Since the invasion of the rubber into the main section 62 is prevented by the sub-section 64, eccentric wear of the rubber caused by the invasion does not occur. The wear resistance of the tire 2 is excellent.

[0078] Since the invasion of the rubber into the main section 62 is prevented by the sub-section 64, eccentric wear of the rubber caused by the invasion does not occur. The wear resistance of the tire 2 is excellent.

[0079] The wet road grip performance, the dry road grip performance, and the wear resistance of the tire 2 according to the present application are excellent. The tire 2 is suitable for running on a race track, and for running on a road. The tire 2 is particularly suitable for running on a race track.

[0080] In Figure 3 ​​In the attached figures, reference numeral L1 represents the distance from the equatorial plane CL to the axial center of the first circumferential groove 34, reference numeral L2 represents the distance from the equatorial plane CL to the axial center of the second circumferential groove 36, and reference numeral L3 represents the distance from the equatorial plane CL to the axial center of the third circumferential groove 38. The aforementioned distances L1, L2, and L3 are measured axially. Appropriate distances L1, L2, and L3 result in superior tire performance of the tire 2. The ratio of distance L1 to the half-width (Tw / 2) of the tread 10 is preferably 25% or more and 60% or less. The ratio of distance L2 to the half-width (Tw / 2) of the tread 10 is preferably 5% or more and 25% or less. The ratio of distance L3 to the half-width (Tw / 2) of the tread 10 is preferably 35% or more and 65% or less.

[0081] A water film easily forms between the rib and the road surface. The surface triangular groove 98 guides the water between the third rib 44 and the road surface towards the second circumferential groove 36. This surface triangular groove 98 inhibits the formation of a water film. As described above, the surface triangular groove 98 has a circumferential dimension that gradually decreases towards the rear side. Therefore, this surface triangular groove 98 does not significantly impede the rigidity of the third rib 44. According to... Figure 3 and Figure 7 It can be seen that the cross-sectional area of ​​the surface-side triangular groove 98 gradually increases along the circumferential direction as it approaches the surface. Therefore, the surface-side triangular groove 98 smoothly guides water to the second circumferential groove 36.

[0082] The dorsal triangular groove 100 guides water between the third rib 44 and the road surface towards the third circumferential groove 38. This dorsal triangular groove 100 inhibits the formation of a water film. As described above, the dorsal triangular groove 100 has a circumferential dimension that gradually decreases towards the surface. Therefore, the dorsal triangular groove 100 does not significantly impede the rigidity of the third rib 44. Figure 3 and Figure 7 It can be seen that the cross-sectional area of ​​the dorsal triangular ditch 100 along the circumference gradually increases as it approaches the dorsal side. Therefore, the dorsal triangular ditch 100 smoothly guides water to the third circumferential ditch 38.

[0083] The groove 102 guides water between the third rib 44 and the road surface towards the surface triangular groove 98 or the back triangular groove 100. This groove 102 improves wet road grip. The groove 102 moderately reduces the rigidity of the third rib 44. Therefore, this groove 102 can improve grip on surfaces with a low coefficient of friction.

[0084] The width of the main segment 62 is W1m (refer to) Figure 4The ratio with respect to the width Tw of the tread surface 24 is preferably 1.0% or more and 5.0% or less. The first circumferential groove 34 having the ratio of 1.0% or more is excellent in the drainage performance. From this viewpoint, the ratio is more preferably 1.5% or more, and particularly preferably 2.0% or more. The first circumferential groove 34 having the ratio of 5.0% or less does not greatly hinder the rigidity of the tread 10. From this viewpoint, the ratio is more preferably 4.5% or less, and particularly preferably 4.0% or less. The width Tw of the tread surface 24 is related to the displacement of the engine of the vehicle 4, and in turn, the displacement is related to the force applied to the tire 2 at the time of turning. In other words, the width Tw of the tread surface 24 is related to the force applied to the tire 2 at the time of turning. From this viewpoint, in the present application, the ratio of the width of each groove and the inclination angle with respect to the width Tw of the tread surface 24 is specified.

[0085] The width W1m is preferably 2.5 mm or more, more preferably 3.5 mm or more. It is particularly preferably 4.5 mm or more. The width W1m is preferably 13.0 mm or less, more preferably 12.0 mm or less, and particularly preferably 11.5 mm or less.

[0086] The inclination angle θ1f of the front side wall 70 of the first circumferential groove 34 is preferably 45° or less. In the tread 10 in which the inclination angle θ1f is 45° or less, the drainage performance and the rigidity can be compatible. From this viewpoint, the inclination angle θ1f is more preferably 35° or less, and particularly preferably 30° or less. From the viewpoint of the ease of manufacture of the tire 2, the inclination angle θ1f is preferably 0° or more.

[0087] The inclination angle θ1b of the back side wall 72 of the first circumferential groove 34 is preferably 45° or less. In the tread 10 in which the inclination angle θ1b is 45° or less, the drainage performance and the rigidity can be compatible. From this viewpoint, the inclination angle θ1b is more preferably 35° or less, and particularly preferably 30° or less. From the viewpoint of the ease of manufacture of the tire 2, the inclination angle θ1b is preferably 0° or more.

[0088] The inclination angle θ1s of the sub segment 64 is preferably 40° or more and 80° or less. The sub segment 64 having the inclination angle θ1s in this range can contribute to the drainage performance, the rigidity, and the wear resistance. The inclination angle θ1s is more preferably 45° or more, and particularly preferably 50° or more. The inclination angle θ1s is more preferably 75° or less, and particularly preferably 70° or less.

[0089] The width W1s of the sub segment 64 is preferably 0.5 mm or more and 3.0 mm or less. The sub segment 64 having the width W1s in this range can contribute to the drainage performance, the rigidity, and the wear resistance. From this viewpoint, the width W1s is more preferably 0.6 mm or more, and particularly preferably 0.7 mm or more. The width W1s is more preferably 2.0 mm or less, and particularly preferably 1.5 mm or less.

[0090] The difference (θ1s-θ1f) between the tilt angle θ1s of the sub-section 64 and the tilt angle θ1f of the outer sidewall 70 of the main section 62 is preferably 10° or more and 55° or less. A difference (θ1s-θ1f) within this range indicates excellent water drainage, rigidity, and wear resistance of the tire 2. A difference (θ1s-θ1f) is more preferably 15° or more, particularly preferably 20° or more. A difference (θ1s-θ1f) is more preferably 50° or less, particularly preferably 45° or less.

[0091] The width W1s of sub-segment 64 preferably satisfies the following mathematical expression.

[0092] 1.0*cosθ1f≤W1s≤5.0*cosθ1f

[0093] In other words, the ratio of width W1s (mm) to cosθ1f is 1.0 or more and 5.0 or less. Tires 2 that satisfy this mathematical formula have excellent wet and dry grip performance. This ratio is more preferably 1.5 or more, particularly preferably 2.0 or more. This ratio is more preferably 4.5 or less, particularly preferably 4.0 or less.

[0094] The width W2 of the second circumferential trench 36 (refer to) Figure 5 The width of the second circumferential groove 36 is preferably 10 mm or more and 20 mm or less. A width of 10 mm or more contributes to drainage. According to this view, a width of 12 mm or more is more preferred, and a width of 13 mm or more is particularly preferred. A width of 20 mm or less does not significantly impede the rigidity of the tread 10. According to this view, a width of 18 mm or less is more preferred, and a width of 17 mm or less is particularly preferred.

[0095] The ratio (W2 / W1m) of the width W2 of the second circumferential groove 36 to the width W1m of the main section 62 is preferably 1.5 or more and 2.5 or less. This ratio (W2 / W1m) indicates that the tire 2 has excellent wet and dry grip performance within this range. This ratio (W2 / W1m) is more preferably 1.7 or more, particularly preferably 1.8 or more. This ratio (W2 / W1m) is more preferably 2.3 or less, particularly preferably 2.2 or less.

[0096] The ratio of the tilt angle θ2b (degree) of the back sidewall 82 of the second circumferential groove 36 to the width Tw (mm) of the tread surface 24 is preferably 5% or more. When the vehicle 4 turns, a large lateral force is applied to the tire 2. The direction of this lateral force is from the surface side towards the back side. In the tread 10 with a ratio of 5% or more, the rigidity relative to the lateral force is large. The tire 2 has excellent dry road grip performance. According to this view, this ratio is more preferably 10% or more, particularly preferably 13% or more. This ratio is preferably 20% or less. The tilt angle θ2b is preferably 13° or more, more preferably 25° or more, particularly preferably 33° or more. The tilt angle θ2b is preferably 50° or less.

[0097] The ratio of the inclination angle θ2f of the surface sidewall 80 to the inclination angle θ2b of the back sidewall 82 in the second circumferential trench 36 is preferably 90% or less. A cross-sectional area of ​​the second circumferential trench 36 with this ratio of 90% or less is sufficiently large. This second circumferential trench 36 contributes to wet road grip performance. From this perspective, this ratio is more preferably 85% or less, particularly preferably 80% or less. The ratio is preferably 60% or more. The inclination angle θ2f is preferably 5° or more, more preferably 15° or more, particularly preferably 20° or more. The inclination angle θ2f is preferably 45° or less.

[0098] The width W3 of the third circumferential trench 38 (refer to) Figure 6 The width of the third circumferential groove 38 is preferably 10 mm or more and 20 mm or less. A width of 10 mm or more in the third circumferential groove 38 contributes to drainage. According to this view, a width of 12 mm or more in the third circumferential groove 38 is more preferably 13 mm or more in the third circumferential groove 38. A width of 20 mm or less in the third circumferential groove 38 does not significantly impede the rigidity of the tread 10. According to this view, a width of 18 mm or less in the third circumferential groove 38 is more preferably 18 mm or less in the third circumferential groove 38, and more preferably 17 mm or less in the third circumferential groove 38.

[0099] The ratio (W3 / W1m) of the width W3 of the third circumferential groove 38 to the width W1m of the main section 62 is preferably 1.5 or more and 2.5 or less. This ratio (W3 / W1m) indicates that the tire 2 exhibits excellent wet and dry grip performance within this range. This ratio (W3 / W1m) is more preferably 1.7 or more, particularly preferably 1.8 or more. This ratio (W3 / W1m) is more preferably 2.3 or less, particularly preferably 2.2 or less.

[0100] The ratio of the tilt angle θ3b (degree) of the back sidewall 92 of the third groove 38 to the width Tw (mm) of the tread surface 24 is preferably 5% or more. When the vehicle 4 turns, a large lateral force is applied to the tire 2. The direction of this lateral force is from the surface side towards the back side. In the tread 10 with a ratio of 5% or more, the rigidity relative to the lateral force is large. The tire 2 has excellent dry road grip performance. According to this view, this ratio is more preferably 10% or more, particularly preferably 13% or more. This ratio is preferably 20% or less. The tilt angle θ3b is preferably 13° or more, more preferably 25° or more, particularly preferably 33° or more. The tilt angle θ3b is preferably 50° or less.

[0101] The ratio of the inclination angle θ3f of the surface sidewall 90 to the inclination angle θ3b of the back sidewall 92 in the third circumferential trench 38 is preferably 90% or less. A cross-sectional area of ​​the third circumferential trench 38 with this ratio of 90% or less is sufficiently large. This third circumferential trench 38 contributes to wet road grip performance. From this perspective, this ratio is more preferably 85% or less, particularly preferably 80% or less. This ratio is preferably 60% or more. The inclination angle θ3f is preferably 5° or more, more preferably 15° or more, particularly preferably 20° or more. The inclination angle θ3f is preferably 45° or less.

[0102] The width Wtf of the triangular groove 98 on the surface (refer to) Figure 3 The ratio (Wtf / Wr) of the width Wr of the third rib 44 to the width Wr is preferably 0.10 or more and 0.30 or less. A surface triangular groove 98 with a ratio (Wtf / Wr) of 0.10 or more contributes to drainage. More preferably, this ratio (Wtf / Wr) is 0.12 or more, and particularly preferably 0.13 or more. A surface triangular groove 98 with a ratio (Wtf / Wr) of 0.30 or less does not significantly impede the rigidity of the third rib 44. More preferably, this ratio (Wtf / Wr) is 0.25 or less, and particularly preferably 0.22 or less. The width Wtf is preferably 3.0 mm or more, more preferably 5.0 mm or more, and particularly preferably 6.0 mm or more. The width Wtf is preferably 15.0 mm or less, more preferably 12.0 mm or less, and particularly preferably 10.0 mm or less.

[0103] The inclination angle θtf at the bottom of the surface triangular groove 98 (refer to) Figure 7 The angle θtf is preferably 40° or more and 70° or less. A surface triangular groove 98 with an inclination angle θtf of 40° or more contributes to drainage. From this perspective, an inclination angle θtf of 45° or more is more preferred, and particularly preferably 48° or more. A surface triangular groove 98 with an inclination angle θtf of 70° or less does not significantly impede the rigidity of the third rib 44. From this perspective, an inclination angle θtf of 60° or less is more preferred, and particularly preferably 55° or less.

[0104] The width Wtb of the dorsal triangular groove 100 (refer to) Figure 3 The ratio (Wtb / Wr) of the width Wr of the third rib 44 to the width Wr is preferably 0.10 or more and 0.30 or less. A back-side triangular groove 100 with a ratio (Wtb / Wr) of 0.10 or more contributes to drainage. According to this viewpoint, a ratio (Wtb / Wr) of 0.12 or more is more preferred, and particularly preferred to be 0.13 or more. A back-side triangular groove 100 with a ratio (Wtb / Wr) of 0.30 or less does not significantly impede the rigidity of the third rib 44. According to this viewpoint, a ratio (Wtb / Wr) of 0.25 or less is more preferred, and particularly preferred to be 0.22 or less. The width Wtb is preferably 3.0 mm or more, more preferably 5.0 mm or more, and particularly preferred to be 6.0 mm or more. The width Wtf is preferably 15.0 mm or less, more preferably 12.0 mm or less, and particularly preferred to be 10.0 mm or less.

[0105] The inclination angle θtb at the bottom of the dorsal triangular groove 100 (refer to) Figure 7 The angle θtb is preferably 40° or more and 70° or less. A dorsal triangular groove 100 with an inclination angle θtb of 40° or more contributes to drainage. From this perspective, an inclination angle θtb is more preferably 45° or more, and particularly preferably 48° or more. A dorsal triangular groove 100 with an inclination angle θtb of 70° or less does not significantly impede the rigidity of the third rib 44. From this perspective, an inclination angle θtb is more preferably 60° or less, and particularly preferably 55° or less.

[0106] The depth Dp of the tool groove 102 (refer to) Figure 7 The depth is preferably 2.0 mm or more. This groove 102 helps with drainage. From this point of view, the depth is more preferably 2.5 mm or more, and particularly preferably 2.8 mm or more. From the viewpoint of the rigidity of the third rib 44, the depth Dp is preferably 5.0 mm or less.

[0107] The area ratio Ps of the groove is preferably 10% or more and 30% or less. Tread patterns with an area ratio Ps of 10% or more exhibit excellent water drainage. According to this viewpoint, an area ratio Ps of 13% or more is more preferred, and particularly preferred to be 15% or more. Treads 10 with an area ratio Ps of 30% or less exhibit excellent rigidity. According to this viewpoint, an area ratio Ps of 25% or less is more preferred, and particularly preferred to be 22% or less. The area ratio Ps is a unfolded diagram (e.g., Figure 3 The ratio of the total area of ​​all grooves in the tire surface 24 to the imaginary area of ​​the tire surface 24. The imaginary area refers to the area of ​​the tire surface 24 if it were assumed that there were no grooves at all.

[0108] 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 at a standard internal pressure. No load is applied to tire 2 during measurement. In this specification, a standard rim refers to a rim defined according to the specifications upon which tire 2 is based. The "standard rim" in JATMA specifications, the "Design Rim" in TRA specifications, and the "Measuring Rim" in ETRTO specifications are standard rims. In this specification, standard internal pressure refers to the internal pressure defined according to the specifications upon which tire 2 is based. The "maximum air pressure" in JATMA specifications, the "maximum value" described in "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES" in TRA specifications, and the "INFLATION PRESSURE" in ETRTO specifications are standard internal pressures.

[0109]

Example

[0110] The effects of the present invention will be made clear by the following examples, but the present invention should not be interpreted in a limiting way based on the description of these examples.

[0111] [Example 1]

[0112] Manufactured Figures 1-7 The pneumatic tire shown is 255 / 40R18. Details of the tire's tread pattern are shown in Table 1 below. In this tire, the tread width Tw is 254 mm, and the width Wr of the third rib is 40 mm.

[0113] [Examples 2-4]

[0114] Except for setting the specifications of the sub-section of the first circumferential groove as shown in Table 1 below, the tires of Examples 2-4 are obtained by setting them the same as in Example 1.

[0115] [Examples 5-9]

[0116] Except for setting the specifications of the main section of the first circumferential groove as shown in Table 2 below, the tires of Examples 5-9 are obtained by setting them the same as in Example 1.

[0117] [Examples 10-13]

[0118] Except for setting the specifications of the second and third circumferential grooves as shown in Table 3 below, the tires of Examples 10-13 are obtained as in Example 1.

[0119] [Examples 14-21]

[0120] The tires of Examples 14 to 21 were obtained in the same manner as in Example 1, except that the specifications of the table-side triangular grooves and the back-side triangular grooves were set as shown in Tables 4 and 5 below.

[0121] [Examples 22 and 23]

[0122] The tires of Examples 22 and 23 were obtained in the same manner as in Example 1, except that the specifications of the sipes were set as shown in Table 6 below.

[0123] [Example 24]

[0124] The tire of Example 24 was obtained in the same manner as in Example 1, except that no sipes were provided.

[0125] [Example 25]

[0126] The tire of Example 25 was obtained in the same manner as in Example 1, except that no table-side triangular grooves, back-side triangular grooves, and sipes were provided.

[0127] [Comparative Example 1]

[0128] The tire of Comparative Example 1 was obtained in the same manner as in Example 1, except that the first circumferential groove having no secondary section was provided.

[0129] [Comparative Example 2]

[0130] The tire of Comparative Example 2 was obtained in the same manner as in Example 1, except that the first circumferential groove having no secondary section was provided, and the specifications of the primary section were set as shown in Table 7 below.

[0131] [Comparative Example 3]

[0132] The tire of Comparative Example 3 was obtained in the same manner as in Example 1, except that no first circumferential groove was provided.

[0133] [Comparative Example 4]

[0134] The tire of Comparative Example 4 was obtained in the same manner as in Example 1, except that the specifications of the first, second, and third circumferential grooves were set as shown in Table 7 below.

[0135] [Drainage Performance]

[0136] The tire was assembled to a rim having a size of "18 x 8.5J". The tire was inflated with air in such a manner that the internal pressure became 220 kPa. The rim was mounted to a four-wheel drive vehicle having a displacement of 2000 cc. The vehicle was made to turn on a road surface having a water pool with a depth of 5 mm, and the lateral force was measured. The results are shown in Tables 1 to 7 below as an index in which Comparative Example 2 is set to 100. The tire having a large index has excellent drainage performance.

[0137] [Graspability on wet road]

[0138] At the time of the above-mentioned drainage performance test, the driver was asked to evaluate the graspability. The results are shown in Tables 1-7 below as an index with Comparative Example 2 being 100. The tire with a large index has excellent graspability on a wet road.

[0139] [Handling stability]

[0140] At the time of the above-mentioned drainage performance test, the driver was asked to evaluate the handling stability. The results are shown in Tables 1-7 below as an index with Comparative Example 2 being 100. The tire with a large index has excellent handling stability.

[0141] [Graspability on dry road]

[0142] The above-mentioned vehicle was made to run on a dry road surface in a circular track, and the driver was asked to evaluate the graspability. The results are shown in Tables 1-7 below as an index with Comparative Example 2 being 100. The tire with a large index has excellent graspability on a dry road.

[0143] [Resistance to wear]

[0144] The above-mentioned vehicle was made to run on a dry road surface in a circular track. When the running distance reached 20 km, the tread surface was visually observed, and the degree of uneven wear was evaluated. The results are shown in Tables 1-7 below as an index with Comparative Example 2 being 100. The tire with a large index has excellent resistance to wear.

[0145] [Table 1]

[0146] Table 1 Evaluation Results

[0147]

[0148] [Table 2]

[0149] Table 2 Evaluation Results

[0150]

[0151] [Table 3]

[0152] Table 3 Evaluation Results

[0153]

[0154] [Table 4]

[0155] Table 4 Evaluation Results

[0156]

[0157] [Table 5]

[0158] Table 5 Evaluation Results

[0159]

[0160] Table 6

[0161] Table 6 Evaluation Results

[0162]

[0163] Table 7

[0164] Table 7 Evaluation Results

[0165]

[0166] As shown in Tables 1 to 7, the total scores of the tires of each example are large. According to the evaluation results, the superiority of the present application is obvious.

[0167] Industrial Applicability

[0168] The tire according to the present application can be mounted on various vehicles.

Claims

1. A tire having a tread surface, wherein, The tread has: The first circumferential groove is located on the surface side of the tire, which is closer to the equatorial plane. The second circumferential trench is located on the back side of the equatorial plane; as well as The third circumferential ditch is located on the back side compared to the second circumferential ditch. The first circumferential trench has: The main segment has a frontal sidewall and a back sidewall; as well as The secondary segment extends from the outer sidewall to the tread surface, and its tilt angle θ1s is greater than the tilt angle θ1f of the outer sidewall. The width W1m of the main section is smaller than the width W2 of the second circumferential trench and smaller than the width W3 of the third circumferential trench. When the inclination angle of the sidewall is set to θ1f, the width W1s of the sub-segment satisfies the following mathematical formula: 1.0*cosθ1f≤W1s≤5.0*cosθ1f.

2. The tire according to claim 1, wherein, The ratio of the width W1m of the main section to the width Tw of the tread surface is more than 1.0% and less than 5.0%.

3. The tire according to claim 1 or 2, wherein, The inclination angle θ1f of the surface sidewall is greater than 0° and less than 45°.

4. The tire according to claim 1 or 2, wherein, The tilt angle θ1s of the sub-segment is greater than 40° and less than 80°.

5. The tire according to claim 1 or 2, wherein, The second circumferential trench has a front sidewall and a back sidewall. The ratio of the tilt angle θ2b of the back sidewall to the width Tw of the tread surface is more than 5% and less than 20%. The ratio of the tilt angle θ2f of the front sidewall to the tilt angle θ2b of the back sidewall is more than 60% and less than 90%.

6. The tire according to claim 1 or 2, wherein, The third circumferential trench has a front sidewall and a back sidewall. The ratio of the tilt angle θ3b of the back sidewall to the width Tw of the tread surface is more than 5% and less than 20%. The ratio of the inclination angle θ3f of the front sidewall to the inclination angle θ3b of the back sidewall is more than 60% and less than 90%.

7. The tire according to claim 1 or 2, wherein, It also has: The surface triangular groove extends from the second circumferential groove toward the dorsal side and has a circumferential dimension and a depth that gradually decrease toward the dorsal side; and The dorsal triangular groove extends from the third circumferential groove toward the surface and has a circumferential dimension and a depth that gradually decreases toward the surface.

8. The tire according to claim 7, wherein, The ratio of the width Wtf of the surface triangular groove to the width Wr of the rib sandwiched between the second circumferential groove and the third circumferential groove is 0.10 or more and 0.30 or less. The ratio of the width Wtb of the dorsal triangular groove to the width Wr of the rib is greater than 0.10 and less than 0.

30.

9. The tire according to claim 7, wherein, The inclination angle θtf at the bottom of the triangular groove on the surface is greater than 40° and less than 70°. The inclination angle θtb at the bottom of the dorsal triangular groove is greater than 40° and less than 70°.

10. The tire according to claim 7, wherein, It also has a cutting groove that connects the front triangular groove and the back triangular groove.

11. The tire according to claim 10, wherein, The depth Dp of the cutting groove is 2.0 mm or more.

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