JP2016033013A - Pneumatic tire for running on off-road - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for running on an off-road, which keeps grip force and traction performance in turning and in which angularity is reduced to improve lightness in handling.SOLUTION: A pneumatic tire for running on an off-road includes, in a tread part 2, a block pattern in which a plurality of blocks 11 are provided. The block 11 includes a center block 12, a shoulder block 13, and a middle block 14. The block 11 includes a tread 15 and a wall surface 16. At least one of the middle block 14 and the shoulder block 13 includes laterally oriented U-shaped blocks 18 each having a recessed groove 17.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire for running on rough terrain, which maintains a gripping force and traction performance during turning and reduces cornering and improves handling lightness.

  For a vehicle traveling on rough terrain such as a motocross bike or a rally car, a pneumatic tire having a block pattern in which a plurality of blocks are provided in a tread portion is usually used. The tire having such a block pattern can secure a driving force in a soft muddy area as the block bites into the road surface.

  In addition, in order to further improve the running performance on rough terrain, a pneumatic tire in which a recess is provided on a tread surface or a wall surface of a block has been proposed (for example, Patent Document 1 below). In such a pneumatic tire, the concave portion provided in the block increases the edge component and improves the grip force and the traction performance.

JP 2008-120351 A

  However, the pneumatic tire as described above has a relatively large rigidity on the tread end side of the block, for example. Such a bias in rigidity gives the driver a “horny feeling” which is a harsh feel operability during turning, and has a problem of worsening handling ease.

  The present invention has been devised in view of the actual situation as described above, and is a lateral U-shaped block having a groove that extends from the wall surface on the tread end side to the tire equator side on the middle block or shoulder block. The main purpose is to provide a pneumatic tire for running on rough terrain that can improve the lightness of handling by reducing the angular tension while maintaining the grip and traction performance during turning. It is said.

  The present invention is a pneumatic tire for running on rough terrain having a block pattern in which a plurality of blocks are provided in the tread portion, and the block is a center block disposed in a central portion of the tread portion; A shoulder block disposed along a tread edge; and a middle block disposed in a region between the center block and the shoulder block, wherein the block includes a tread surface facing outward in a tire radial direction, and the tread surface A wall extending from the edge of the tire to the inside in the tire radial direction, and the shoulder block has a concave groove extending from the wall surface at the tread end side to the tire equator side at a substantially middle portion in the tire circumferential direction. A laterally U-shaped block, and an inverted U-shaped block having a concave groove extending from the wall surface on the tire equator side to the tread end side, Characterized in that it contains.

  In the pneumatic tire for traveling on rough terrain of the present invention, it is desirable that the tread surface of the U-shaped block has a vertically long shape in which the maximum length in the tire circumferential direction is larger than the maximum length in the tire axial direction.

  In the pneumatic tire for traveling on rough terrain of the present invention, the tread surface of the U-shaped block includes an inner edge extending along the tire equator side along the tire circumferential direction, an outer edge on the tread end side, and the inner edge. A first circumferential end edge and a second circumferential end edge extend between the outer edges on both ends in the tire circumferential direction of the block, and the outer edge extends from the concave groove to the first. A first outer edge portion inclined toward the tire equator side toward the circumferential end edge; and a second outer edge portion inclined toward the tire equator side from the concave groove toward the second circumferential end edge. Is desirable.

  In the pneumatic tire for traveling on rough terrain of the present invention, the tread surface of the U-shaped block includes an inner edge extending along the tire equator side along the tire circumferential direction, an outer edge on the tread end side, and the inner edge. A first circumferential end edge and a second circumferential end edge extending between the outer edges on both ends in the tire circumferential direction of the block, the first circumferential end edge and the second circumferential edge. It is desirable that the circumferential end edge is inclined in a direction away from the tire equator side toward the tread end side.

  In the pneumatic tire for traveling on rough terrain of the present invention, the tread surface of the U-shaped block includes an inner edge extending along the tire equator side along the tire circumferential direction, an outer edge on the tread end side, and the inner edge. A first circumferential end edge and a second circumferential end edge extending between the outer edges on both ends in the tire circumferential direction of the block, the first circumferential end edge and the inner edge It is desirable that a chamfered portion is provided in each of the corner portion formed by the edge portion and the corner portion formed by the second circumferential end edge and the inner edge.

  In the pneumatic tire for traveling on rough terrain according to the present invention, it is desirable that the chamfered portion has an arc shape having a radius of curvature of 2 mm or less that is convex toward the center side of the tread surface.

  The pneumatic tire for running on rough terrain according to the present invention has a groove in which at least one of the middle block or the shoulder block extends from the wall surface on the tread end side to the tire equator side at a substantially middle portion in the tire circumferential direction. Including a horizontally oriented U-shaped block. Such a block ensures a large edge component and maintains the grip force and traction performance during turning. Further, the rigidity of the tread end side of such a block is relaxed by the concave groove. Therefore, in the tire of the present invention, the tread end side of the U-shaped block is appropriately deformed at the time of turning, and the angular feeling can be reduced, and the handling lightness and the feeling of grounding at the time of turning can be improved.

It is sectional drawing of the pneumatic tire which shows one Embodiment of this invention. FIG. 2 is a development view of the tread portion of FIG. 1. It is an expansion perspective view of the U-shaped block of FIG. It is an enlarged plan view of a U-shaped block. It is BB sectional drawing of FIG. (A) is an enlarged plan view of the block of a comparative example, (b) is an enlarged plan view of the block of another comparative example. (A) is an enlarged plan view of another comparative example, and (b) is a CC cross-sectional view of (a).

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a pneumatic tire (hereinafter simply referred to as “tire”) 1 for traveling on rough terrain according to the present embodiment, which is designed to exhibit the best performance on soft roads such as sand and muddy ground. The motocross competition (motorcycle) tire is exemplified. 1 is a cross-sectional view taken along line AA of FIG. 2 in a normal state in which the tire 1 is mounted on a normal rim (not shown) and is filled with a normal internal pressure and is unloaded. is there.

  Here, the “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, a standard rim for JATMA and a “Design Rim” for TRA. Or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure specified by the tire for each tire. The maximum air pressure for JATMA is the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for TRA. If it is ETRTO, it means "INFLATION PRESSURE". In the present specification, unless otherwise specified, the dimensions of each part of the tire are values specified in the normal state.

  As shown in FIG. 1, the tire 1 includes a tread portion 2, a pair of sidewall portions 3 and 3 extending inward in the tire radial direction from both sides thereof, and inner sides in the tire radial direction of the respective sidewall portions 3. It has bead parts 4 and 4 which are located in an end and are equipped with a rim (not shown). Further, the tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a tread reinforcing layer disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. 7 and is reinforced.

  The tread portion 2 of the present embodiment has an outer surface that is convex and curved outward in the tire radial direction, and a tread width TW that is a tire axial distance between the tread ends Te and Te of the tread portion 2 is a tire maximum width. I am doing.

  The carcass 6 includes a main body portion 6a straddling a pair of bead cores 5 and 5 in a toroidal shape, and a turn-back portion 6b connected to both sides of the main body portion 6a and folded back from the inner side in the tire axial direction around the bead core 5. One or more of them, in this embodiment, one carcass ply 6A. Further, a bead apex 8 made of hard rubber extending from the bead core 5 to the outside in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A, and the bead portion 4 is appropriately reinforced.

  In the tread portion 2, a plurality of blocks 11 and a tread groove 10 between them are formed. The groove bottom surface 10 b of the tread groove 10 is formed on a smooth surface along the outer surface of the carcass 6. Further, the groove depth D1 of the tread groove 10 is set to about 7 to 19 mm, for example.

  The block 11 includes a center block 12, a shoulder block 13 disposed along the tread end Te, and a middle block 14 disposed between the center block 12 and the shoulder block 13. Each of these blocks 12, 13, 14 includes a tread surface 15 facing outward in the tire radial direction and a wall surface 16 extending from the edge of the tread surface 15 inward in the tire radial direction.

  As shown in FIG. 2, the center block 12 is disposed in the central portion Cr of the tread portion 2. The center portion Cr means a region of 25% of the tread development width TWe centered on the tire equator C. In the center block 12 of this embodiment, 60% or more of the surface area of the tread surface 15 is provided in the center portion Cr.

  The center block 12 of the present embodiment includes a first block 21 having a slit 20 extending in the circumferential direction of the tire in a substantially rectangular central portion that is long in the tire axial direction, and a first block 21 that is symmetrically disposed on both sides of the tire equator C. 2 blocks. In addition, a center concave portion 34 in which the groove bottom surface 10 b of the tread groove 10 is locally recessed is disposed between the first block 21 and the second block 22. The first block 21, the second block 22, and the center recess 34 are spaced apart in the tire circumferential direction in the center portion Cr, so that the soil removal property of the tread portion 2 is maintained. The grip power is improved.

  The shoulder block 13 is disposed along the tread end Te. Thereby, 60% or more of the surface area of the tread surface 15 is disposed in the shoulder block 13 from the tread end Te to the end region Sh that is 20% of the tread development half width TWh. The tread development half width TWh means the tread development length from the tire equator C to the tread end Te.

  In the middle block 14, 60% or more of the surface area of the tread surface 15 of the middle block 14 is arranged in an intermediate region Md that is a region between the central portion Cr and the end region Sh.

  At least one of the middle block 14 or the shoulder block 13 includes a lateral U-shaped block 18 having a concave groove 17 extending from the wall surface 16 on the tread end Te side to the tire equator C side. Note that “laterally” means the direction when the tire circumferential direction is “vertical”.

  FIG. 3 shows an enlarged perspective view of the U-shaped block 18, and FIG. 4 shows an enlarged plan view of the tread. Further, FIG. 5 shows a cross-sectional view taken along the line BB of FIG. As shown in FIGS. 3 to 5, the U-shaped block 18 includes a concave groove 17 extending from the wall surface 16 on the tread end side to the tire equator side at a substantially middle portion in the tire circumferential direction.

  Such a concave groove 17 ensures a large edge component of the U-shaped block 18. For this reason, the grip force and traction performance during turning are maintained. Further, the U-shaped block 18 having such a concave groove 17 is relaxed in rigidity at the tread end side. For this reason, the U-shaped block 18 is deformed on the tread end side of the block at the time of turning, thereby reducing the angular feeling, and thus improving the lightness of handling and the feeling of grounding at the time of turning.

  The concave groove 17 needs to be provided at a substantially middle portion of the length of the U-shaped block 18 in the tire circumferential direction. Such a concave groove 17 appropriately moderates the rigidity of the U-shaped block 18 on the tread end side while suppressing the chipping of the U-shaped block 18. Moreover, the aspect in which the concave groove 17 is provided in the substantially middle portion of the length in the tire circumferential direction of the U-shaped block 18 is, as shown in FIG. 4, an axial center line 18c of the U-shaped block 18 This means that the groove deviation amount L5, which is the distance in the tire circumferential direction from the groove center line 17c of the groove 17, is within 25% of the maximum length L1 of the tread surface 15 in the tire circumferential direction. The axial center line 18c of the U-shaped block 18 is a tire axial line that is equidistant from both the tire axial lines 18L and 18L passing through the outer ends 18e and 18e on both sides in the tire circumferential direction of the U-shaped block 18. Means. In the present embodiment, an example in which the axial center line 18c of the U-shaped block and the groove center line 17c of the concave groove 17 overlap, that is, an example in which the concave groove displacement amount L5 is zero is shown. In addition, from the viewpoint of suppressing block chipping or the like, it is desirable that the groove ditch amount L5 is 5% or less of the maximum length L1 of the U-shaped block 18 in the tire circumferential direction.

  As shown in FIGS. 3 and 4, the tread surface 15 of the U-shaped block 18 includes an inner edge 24 extending along the tire circumferential direction on the tire equator C side, and both end portions of the U-shaped block 18 in the tire circumferential direction. It has an axial edge 35 extending in the tire axial direction on the side, and an outer edge 25 on the tread end side facing the inner edge 24.

  The inner edge 24 exerts a frictional force in the tire axial direction on the road surface and improves the grip during turning. From such a viewpoint, it is desirable that the inner edge 24 extends parallel to the tire circumferential direction.

  The axial edge 35 is formed between the inner edge 24 and the outer edge 25 at the first circumferential end edge 26 and the second circumference extending in the tire axial direction on both ends in the tire circumferential direction of the U-shaped block 18. A directional edge 27 is included. In the present embodiment, the first circumferential end edge 26 and the second circumferential end edge 27 are inclined in a direction away from each other from the tire equator C side toward the tread end side. The first circumferential end edge 26 and the second circumferential end edge 27 as described above secure a large length in the tire circumferential direction of the outer edge 25 and improve the grip force during turning. Further, the first circumferential end edge 26 and the second circumferential end edge 27 are inclined in opposite directions with respect to the tire axial direction, and are inclined at the same angle with respect to the tire axial direction. The first circumferential end edge 26 and the second circumferential end edge 27 as described above make the feeling of ground contact during acceleration and deceleration constant and improve steering stability.

  The outer edge 25 is inclined from the concave groove 17 toward the first circumferential end edge 26 toward the tire equator C side, and from the concave groove 17 toward the second circumferential end edge 27. And a second outer edge portion 29 inclined toward the tire equator C side. The first outer edge portion 28 and the second outer edge portion 29 are preferably symmetrical with respect to the axial center line 18 c of the U-shaped block 18. Such first outer edge portion 28 and second outer edge portion 29 improve the stability of the block in addition to improving the handling stability by making the feeling of grounding at the time of acceleration and deceleration constant.

  The tread surface 15 of the U-shaped block 18 preferably has a vertically long shape in which the maximum length L1 in the tire circumferential direction is longer than the maximum length W1 in the tire axial direction. Such a U-shaped block 18 includes a lot of edge components extending in the tire circumferential direction, and exhibits a grip force during turning. In addition, in the tread 15 of the U-shaped block 18, it is desirable that the maximum length L1 in the tire circumferential direction is set to 9 to 30 mm, for example. The maximum length W1 of the tread surface 15 in the tire axial direction is preferably set to 10 to 30 mm, for example.

  The groove center line 17c of the recessed groove 17 is preferably at an angle of ± 10 ° or less with respect to the tire axial direction. As a result, the rigidity on the tread end side of the U-shaped block 18 can be relaxed with a good balance.

  As shown in FIG. 4, when the groove width W2 of the concave groove 17 is decreased, the angular feeling may not be sufficiently reduced. When the groove width W2 is increased, the rigidity of the U-shaped block 18 is decreased, and the block chipping, etc. May occur. From such a viewpoint, the groove width W2 of the concave groove 17 is preferably set to 0.10 times or more of the maximum length L1 of the tread surface 15 in the tire circumferential direction, and preferably 0.30 times or less. Preferably it is set to 0.20 times or less. The groove width W2 of the concave groove 17 means the maximum width of the groove width of the concave groove 17.

  From the same viewpoint, the length L2 of the groove 17 in the tire axial direction is set to 0.15 times or more, more preferably 0.30 times or more, the maximum width W1 of the tread surface 15 in the tire axial direction. It is set to 0.50 times or less, more preferably 0.35 times or less.

  Further, it is desirable that the tire axial direction length L2 of the concave groove 17 is smaller than the width W3 of the concave groove 17 from the inner end 17o in the tire axial direction to the inner edge 24 in the tire axial direction. Such a concave groove 17 can secure the rigidity of the U-shaped block 18 and maintain the grip force and traction performance during turning, and can improve the block durability.

  As shown in FIG. 5, when the groove depth d1 of the concave groove 17 is reduced, the rigidity on the tread end side of the U-shaped block 18 is not relaxed, and there is a possibility that the squareness may not be suppressed. There is a risk that the rigidity of the U-shaped block 18 in the tire circumferential direction is lowered and the traction performance is lowered. From such a viewpoint, the groove depth d1 is preferably set to 0.60 times or more, more preferably 0.70 times or more, and more preferably 0.90 times or less of the groove depth D1 of the tread groove 10. More preferably, it is set to 0.80 times or less.

  As shown in FIG. 3, the concave groove 17 forms lateral edges 17 s and 17 s extending from the first outer edge portion 28 and the second outer edge portion 29 to the tire equator C side on the tread surface 15. Further, the concave groove 17 forms a vertical edge 17v extending from the tread surface 15 inward in the tire radial direction on the wall surface 16 on the tread end side. For example, in the case of a straight line, the horizontal edge 17s and the vertical edge 17v exhibit a high edge effect and prevent the groove 17 from biting into the stone. In particular, it is desirable that the lateral edges 17s, 17s are inclined in a direction away from each other toward the tread end side. Similarly, it is desirable that the vertical edges 17v, 17v be inclined in a direction away from each other toward the outer side in the tire radial direction.

  The lateral edges 17s and 17s extend toward the tire equator C side and are continuous with the arc edge 17r. Similarly, the vertical edges 17v and 17v extend inward in the tire radial direction and are continuous with the arc edge 17r. The arc edge 17r serves to relieve stress when the U-shaped block 18 is deformed.

  The U-shaped block 18 preferably has an edge component extending in the tire radial direction on the wall surface 16. From this point of view, the corner portion 30 formed by the first circumferential end edge 26 and the inner edge 24 and the corner portion 31 formed by the second circumferential end edge 27 and the inner edge 24 are respectively provided with surfaces. A take section 32 is provided. Such a chamfered portion 32 can suppress block missing of the U-shaped block 18.

  The chamfered portion 32 preferably has an arc shape that is convex toward the center side of the tread surface 15, and the curvature radius r is preferably 2 mm or less. Further, the U-shaped block 18 is formed with an arcuate recess 33 extending from the chamfered portion 32 inward in the tire radial direction. Such an arc-shaped depression 33 improves the gripping force and traction performance particularly in a soft muddy area.

  As is apparent from FIG. 4, when the chamfered portion 32 is increased, the length of the inner edge 24 extending parallel to the tire circumferential direction is reduced, and the grip force during turning may be reduced. On the other hand, if the chamfered portion 32 is small, the effect of the chamfered portion 32 may be reduced. From such a viewpoint, the length L4 in the tire circumferential direction of the inner edge 24 is an intersection of the extension line of the first circumferential end edge 26 and the second circumferential end edge 27 and the extension line of the inner edge 24. It is preferably set to 0.60 times or more, more preferably 0.65 times or more, and preferably 0.80 times or less, more preferably 0.80 times or more of the virtual inner edge length L3, which is the distance in the tire circumferential direction between them. It is desirable to set it to 75 times or less.

  Further, the virtual inner edge length L3 is preferably set to 0.75 times or more, more preferably 0.80 times or more, and preferably 1.00 times or less of the maximum length L1 of the tread surface 15 in the tire circumferential direction. More preferably, it is set to 0.90 times or less. Such a U-shaped block 18 can appropriately increase the rubber volume on the tread end side, and improves the grip force during turning.

  In order to ensure that the above-described effect of the U-shaped block 18 is exhibited from the beginning of the turn to the end of the turn, it is desirable that the middle block 14 is composed of the U-shaped block 18 as shown in FIG. .

  The shoulder block 13 of the present embodiment includes a U-shaped block 18 and an inverted U-shaped block 19 having a concave groove 17 extending from the wall surface 16 on the tire equator C side to the tread end side. Such a shoulder block 13 improves a feeling of grounding when the vehicle body is raised while improving a grip force in the vicinity of the full bank.

  Furthermore, it is desirable that the shoulder block 13 made of the U-shaped block 18 and the middle block 14 made of the U-shaped block 18 are alternately provided in the tire circumferential direction. The shoulder block 13 and the middle block 14 improve the soil removal performance of the tread portion 2 when traveling on a muddy ground, and exhibit a grip force and traction performance during turning with a good balance.

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

  A pneumatic tire for a motorcycle for running on rough terrain having the basic structure shown in FIG. 1 and having the tread pattern of FIG. 2 as a basic pattern was prototyped based on the specifications shown in Table 1. These prototype tires were mounted on the front wheels of a test vehicle and tested for performance.

As comparative examples, the following comparative examples 1 to 3 having the basic structure shown in FIG. 1 and having different block shapes were also tested in the same manner. In Comparative Examples 1 to 3, the U-shaped blocks of the tread pattern in FIG. 2 are all changed to the following block shapes. Except for the shape of the block, it is the same as the tread pattern of FIG.
Comparative example 1: Block b1 which does not have a ditch | groove and a chamfer part shown by Fig.6 (a).
Comparative example 2: Block b2 which does not have a ditch | groove and has a chamfer c shown in FIG. 6 (b).
Comparative example 3: Block b3 which does not have a ditch | groove and a chamfer part but has a recessed part (recess) d in a tread surface shown by FIG. 7 (a) and (b).

In addition, the common specification of an Example and a comparative example is as follows.
tire size:
Front wheel: 80 / 100-21
Rear wheel: 120 / 80-19
Rim size:
Front wheel: 21 x 1.60
Rear wheel: 19 x 2.15
internal pressure:
Front wheel: 80 kPa
Rear wheel: 80 kPa
Test vehicle: displacement 450cc motocross competition vehicle The test method is as follows.

<Grip power during turning, traction performance, squareness, and lightness in handling>
Under the above conditions, the grip strength, traction performance, angular feeling, and lightness of handling when running on a rough road test course were tested by the driver's sensory evaluation. A result is a score which sets the comparative example 3 to 100, and shows that it is so favorable that a numerical value is large.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tires of the examples maintained the gripping force and traction performance during turning while suppressing the angular tension and improving the lightness of handling.

6 Carcass 12 Center block 13 Shoulder block 14 Middle block 15 Tread surface 16 Wall surface 17 Groove 18 U-shaped block 19 Reverse U-shaped block 24 Inner edge 25 Outer edge

Claims (6)

A pneumatic tire for running on rough terrain having a block pattern in which a plurality of blocks are provided in the tread portion,
The block includes a center block disposed in a central portion of the tread portion, a shoulder block disposed along a tread end, and a middle block disposed in a region between the center block and the shoulder block. Including
The block includes a tread surface that faces the outer side in the tire radial direction, and a wall surface that extends inward in the tire radial direction from an edge of the tread surface,
The shoulder block includes a lateral U-shaped block having a concave groove extending from the wall surface on the tread end side to the tire equator side at a substantially middle portion in the tire circumferential direction, and the wall surface on the tire equator side. A pneumatic tire for running on rough terrain, comprising an inverted U-shaped block having a concave groove extending from the side to the tread end side.   The pneumatic tire for running on uneven terrain according to claim 1, wherein the tread surface of the U-shaped block has a vertically long shape in which the maximum length in the tire circumferential direction is larger than the maximum length in the tire axial direction. The tread of the U-shaped block has an inner edge extending along the tire circumferential direction on the tire equator side, an outer edge on the tread end side,
A first circumferential end edge and a second circumferential end edge extending between the inner edge and the outer edge on both ends in the tire circumferential direction of the block;
The outer edge includes a first outer edge portion inclined toward the tire equator side from the concave groove toward the first circumferential end edge, and a tire equator from the concave groove toward the second circumferential end edge. The pneumatic tire for running on uneven terrain according to claim 1 or 2, comprising a second outer edge portion inclined to the side. The tread of the U-shaped block has an inner edge extending along the tire circumferential direction on the tire equator side, an outer edge on the tread end side,
A first circumferential end edge and a second circumferential end edge extending between the inner edge and the outer edge on both ends in the tire circumferential direction of the block;
The said 1st circumferential direction edge part edge and the said 2nd circumferential direction edge part edge are inclined in the direction which mutually separates toward the tread edge side from a tire equator side. Pneumatic tire for leveling. The tread of the U-shaped block has an inner edge extending along the tire circumferential direction on the tire equator side, an outer edge on the tread end side,
A first circumferential end edge and a second circumferential end edge extending between the inner edge and the outer edge on both ends in the tire circumferential direction of the block;
A corner portion formed by the first circumferential end edge and the inner edge and a corner portion formed by the second circumferential end edge and the inner edge are each provided with a chamfered portion. The pneumatic tire for rough terrain travel according to any one of claims 1 to 3.   The pneumatic tire for rough terrain travel according to claim 5, wherein the chamfered portion has an arc shape with a radius of curvature of 2 mm or less that is convex toward the center side of the tread surface.

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