JP5994527B2 - Heavy duty pneumatic tire - Google Patents

Description

  The present invention relates to a heavy duty pneumatic tire with improved cut chipping resistance.

  Conventionally, for example, a heavy-duty pneumatic tire described in Patent Document 1 includes a cap tread rubber composed of a wear-resistant rubber layer on the outermost surface of the tread portion, and an under tread rubber composed of a low heat-generating rubber layer inside the tread portion. It consists of. Further, in this heavy-duty pneumatic tire, sipes extending from the outermost surface side rubber layer to the inner surface side rubber layer and extending in the tire width direction are provided at predetermined intervals in the tire circumferential direction at both shoulder ends of the tread portion. Is formed.

JP 2010-23742 A

  In a heavy-duty pneumatic tire, a sipe may be provided at the opening edge of the main groove extending in the tire circumferential direction in order to improve uneven wear resistance. However, in the heavy-duty pneumatic tire having the low heat-generating rubber layer (under tread rubber) in the tread portion described in Patent Document 1 described above, there is a possibility that cut chipping may occur from the sipe as a starting point after the middle period of wear. The under tread rubber is weak against cut chipping, and it is considered that one of the causes is that the cut chipping easily grows from the sipe end when the under tread rubber is exposed after the middle stage of wear.

  This invention is made | formed in view of the above, Comprising: It aims at providing the heavy-duty pneumatic tire which can improve cut-chipping-proof performance.

  In order to solve the above-described problems and achieve the object, the heavy-duty pneumatic tire of the present invention includes a plurality of land portions extending in the tire circumferential direction by a plurality of main grooves extending along the tire circumferential direction. A cap tread rubber disposed on a tread surface having a tire tread rubber and a tire tread rubber inner side in the tire radial direction, and at a land portion on a side of the main groove, on the outer side in the tire radial direction than a groove bottom of the main groove. A heavy-duty pneumatic tire having a tread portion composed of an undertread rubber disposed and having a sipe that opens to a groove wall of the main groove and the tread surface and terminates at the land portion on the side of the main groove. The sipe is provided in the region of the cap tread rubber, and the groove depth d of the sipe with respect to the groove depth D of the main groove on the inner side in the tire radial direction from the tread surface is 0.5 ≦ d / D ≦ 1. And the groove width of the sipe in the tire width direction from the groove wall of the main groove to the land portion side is gradually reduced from the tread surface toward the inner side in the tire radial direction. To do.

  According to this heavy-duty pneumatic tire, the groove depth d of the sipe is set to 50% or more of the groove depth D of the main groove. Even when the tread portion is worn by 50 [%] or more of the groove depth D of the groove, the effect of improving the uneven wear resistance performance by sipe can be obtained. Moreover, because the sipe is provided in the cap tread rubber region and the groove width of the sipe is gradually reduced from the tread surface toward the inside in the tire radial direction, the sipe is arranged so as to move away from the under tread rubber. Even when the undertread rubber is exposed on the surface of the tread portion after the middle stage of wear, the occurrence of cut chipping starting from sipe can be suppressed.

  In the heavy duty pneumatic tire of the present invention, the sipe is formed such that a groove width on the tread surface is 2 [mm] or more and 5 [mm] or less.

  According to this heavy duty pneumatic tire, the groove width of the sipe on the tread surface is the maximum groove width of the sipe, and by reducing the groove width to 5 mm or less, the groove width is gradually reduced from this dimension. By doing so, the sipe can be reliably moved away from the undertread rubber, so that the effect of improving the cut chipping resistance can be remarkably obtained. Further, by setting the groove width of the sipe on the tread surface to 2 [mm] or more, the uneven wear resistance performance due to the sipe can be remarkably obtained.

  In the heavy duty pneumatic tire of the present invention, the sipe is formed such that the groove width at 50 [%] of the groove depth D of the main groove is 60 [%] or less of the groove width on the tread surface. It is characterized by that.

  According to this heavy-duty pneumatic tire, the groove width of the sipe is 60 [% of the groove width on the tread surface after the middle wear period when the tread portion is worn 50% or more of the groove depth D of the circumferential main groove. ] Since the sipe can be surely moved away from the undertread rubber, the effect of improving the cut chipping resistance can be remarkably obtained.

  In the heavy-duty pneumatic tire of the present invention, the undertread rubber is disposed in a range radially inward from 50% of the groove depth D of the main groove in the land portion. To do.

  It is desirable to set the sipe groove width as appropriate in order to obtain outstanding wear resistance performance due to sipe.To obtain cut chipping performance, reduce the sipe groove width and keep the sipe away from the under tread rubber. Is desirable. For this reason, by placing the under tread rubber on the inner side in the tire radial direction from 50 [%] of the groove depth D of the main groove in the land portion, the under tread rubber is exposed to the surface of the tread portion of the under tread rubber before the middle period of wear. In this way, it is possible to significantly obtain uneven wear resistance due to a sipe having an appropriate groove width, and to significantly obtain cut chipping performance due to a sipe having a reduced groove width after the middle stage of wear.

  The heavy duty pneumatic tire of the present invention is characterized in that the loss tangent tan δC of the cap tread rubber at 60 ° C. and the loss tangent tan δU of the undertread rubber satisfy the relationship of tan δU <tan δC. To do.

  According to this heavy-duty pneumatic tire, in the tread portion, the tread surface is made of cap tread rubber, and the inner side in the tire radial direction of the cap tread rubber is made of under tread rubber. The effect which improves can be acquired notably.

  In the heavy duty pneumatic tire of the present invention, the shortest distance is equal to or greater than the groove width of the sipe at the shortest distance between the end of the sipe and the under tread rubber in the tire width direction. .

  That is, it is preferable that the shortest distance is equal to or greater than the groove width of the sipe at a position where the sipe and the under tread rubber are closest in the tire width direction. According to this heavy-duty pneumatic tire, since the undertread rubber is separated from the sipe by more than the groove width of the sipe, the effect of improving cut chipping resistance can be remarkably obtained.

  The heavy duty pneumatic tire according to the present invention can improve cut chipping resistance.

FIG. 1 is a plan view of a heavy duty pneumatic tire according to an embodiment of the present invention. FIG. 2 is a partially enlarged cross-sectional view of a heavy duty pneumatic tire according to an embodiment of the present invention. FIG. 3 is a partially enlarged cross-sectional view of a heavy duty pneumatic tire according to an embodiment of the present invention. FIG. 4 is a partially enlarged cross-sectional view of a heavy duty pneumatic tire according to an embodiment of the present invention. FIG. 5 is a partially enlarged cross-sectional view of a heavy duty pneumatic tire according to an embodiment of the present invention. FIG. 6 is a partially enlarged cross-sectional view of a heavy duty pneumatic tire according to an embodiment of the present invention. FIG. 7 is a partially enlarged cross-sectional view of a heavy duty pneumatic tire according to an embodiment of the present invention. FIG. 8 is a chart showing the results of performance tests of heavy duty pneumatic tires according to examples of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. Further, a plurality of modifications described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

  FIG. 1 is a plan view of a heavy duty pneumatic tire according to the present embodiment, and FIGS. 2 to 7 are partially enlarged sectional views of the heavy duty pneumatic tire according to the present embodiment.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the heavy-duty pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire diameter The direction outer side means the side away from the rotation axis in the tire radial direction. Further, the tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction means the side toward the tire equator plane (tire equator line) CL in the tire width direction, and the outer side in the tire width direction means the tire width. The direction away from the tire equatorial plane CL in the direction. The tire circumferential direction is a circumferential direction with the rotation axis as a central axis. The tire equatorial plane CL is a plane that is orthogonal to the rotational axis of the heavy duty pneumatic tire 1 and that passes through the center of the tire width of the heavy duty pneumatic tire 1. The tire equator line is a line along the circumferential direction of the heavy duty pneumatic tire 1 on the tire equator plane CL. In the present embodiment, the same sign “CL” as that of the tire equator plane is attached to the tire equator line.

  The heavy-duty pneumatic tire 1 of the present embodiment has a tread portion 2 as shown in FIGS. The tread portion 2 is made of a rubber material, and is exposed at the outermost side in the tire radial direction of the heavy load pneumatic tire 1. The surface of the tread portion 2 is a contour of the heavy load pneumatic tire 1 as a tread surface 2 a. Further, as shown in FIG. 2, the tread portion 2 includes a cap tread rubber C having a tread surface 2a made of a wear-resistant rubber layer and an under tread rubber U made of a low heat-generating rubber layer on the inner side in the tire radial direction. Composed.

  The tread portion 2 has a plurality of circumferential main grooves (main grooves) 3 extending along the tire circumferential direction on the tread surface 2a in parallel with the tire width direction (shown by three in FIG. 1). Yes. The tread portion 2 has a plurality of rib-like land portions 4 (indicated by four in FIG. 1) extending along the tire circumferential direction by a plurality of circumferential main grooves 3 on the tread surface 2a. Yes.

  Further, the tread portion 2 is provided with a secondary groove 5 that intersects with the tire circumferential direction. The sub-groove 5 has a narrower groove width and a smaller groove depth than the circumferential main groove 3. In the present embodiment, the sub-groove 5 is provided at both ends of the land portion 4 between the circumferential main grooves 3 so as to communicate with the circumferential main grooves 3. The sub-groove 5 provided in the land portion 4 between the circumferential main grooves 3 branches into branches on both sides in the tire circumferential direction at the center position in the tire width direction of the land portion 4. It has a branch groove 5a that terminates. Furthermore, the sub-groove 5 has one end communicating with the circumferential main groove 3 at the outermost land portion 4 in the tire width direction and the other end extending beyond the ground contact end T on the outer surface in the tire width direction of the land portion 4. Terminated. In addition, the form of the subgroove 5 is an example, and is not limited to the above configuration.

  Here, the ground contact end T refers to a ground contact region (when the heavy load pneumatic tire 1 is assembled on a regular rim and filled with a regular internal pressure and 70% of the regular load is applied) The tread surface 2a of the tread portion 2 is a region where the tread surface 2a is in contact with the road surface) and the outermost ends in the tire width direction. In FIG. 1, the contact end T is shown continuously in the tire circumferential direction.

  The regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load is “maximum load capacity” defined by JATMA, a maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  As shown in FIG. 2, the circumferential main groove 3 is disposed in the cap tread rubber C of the tread portion 2. Although not shown in the figure, the sub-groove 5 is also disposed in the cap tread rubber C of the tread portion 2. The under-tread rubber U is disposed directly below the circumferential main groove 3 (inner side in the tire radial direction) and on the inner side in the tire radial direction from the groove bottom 3a of the circumferential main groove 3. It arrange | positions so that it may protrude from the groove | channel bottom 3a of the circumferential direction main groove 3 on the tire radial direction, leaving | separating from the groove | channel 3. The under tread rubber U is disposed closest to the circumferential main groove 3 immediately below the circumferential main groove 3 (inner side in the tire radial direction). Such an arrangement of the under tread rubber U is such that when the tire is vulcanized and molded, the mold that forms the circumferential main groove 3 pushes the under tread rubber U inward in the tire radial direction and flows toward the land portion 4 side. Caused by

  In the region of the cap tread rubber C, a sipe 6 is provided on the groove wall 3 b of the circumferential main groove 3. The sipe 6 opens to the groove wall 3 b and the tread surface of the circumferential main groove 3 and is provided to terminate at the land portion 4 on the side of the circumferential main groove 3. As shown in FIG. 1, the sipe 6 is provided in the groove walls 3 b on both sides of the circumferential main groove 3. The sipe 6 has a groove thickness of 1.0 [mm] or less in the tire circumferential direction.

  In the sipe 6, as shown in FIG. 2, the groove depth d with respect to the groove depth D of the circumferential main groove 3 on the inner side in the tire radial direction from the tread surface is in a range of 0.5 ≦ d / D ≦ 1.0. Is provided. Further, the sipe 6 has a tire width direction groove width W that terminates from the groove wall 3b of the circumferential main groove 3 to the land portion 4 side, and a tire diameter from the tread surface 2a to the groove bottom 3a side of the circumferential main groove 3. It is formed to gradually decrease toward the inner side in the direction.

  The form in which the groove width W of the sipe 6 gradually decreases from the tread surface 2a toward the inner side in the tire radial direction is, for example, as shown in FIG. 2 and FIG. There is a form in which FIG. In addition, as shown in FIG. 4 to FIG. 4 shows a form in which the end position in the tire width direction of the sipe 6 is linearly formed in the tire radial direction, and in FIG. 5, the end position in the tire width direction of the sipe 6 is in the tire radial direction on the land portion 4 side. 6 shows a form formed in a curved shape so as to swell, and in FIG. 6, the end position in the tire width direction of the sipe 6 is formed in a curved shape so as to be recessed toward the groove wall 3b side of the circumferential main groove 3 in the tire radial direction. The form which was made is shown. Further, as shown in FIG. 7, the groove width W is constant in a predetermined range inside the tire radial direction from the tread surface 2a, and the groove width W gradually decreases steplessly from the middle toward the inside in the tire radial direction. May be. Further, as shown in FIGS. 2 and 3, the sipe 6 may be formed leaving a predetermined groove width W at an end portion in the tire radial direction closest to the groove bottom 3 a of the circumferential main groove 3. As shown in FIGS. 4 to 7, the groove width W may be zero.

  In the above-described heavy load pneumatic tire 1, in the tread portion 2, the tread surface 2 a is a cap tread rubber C made of a wear-resistant rubber layer, and the inner side in the tire radial direction of the cap tread rubber C is an underwear made of a low heat-generating rubber layer. By using the tread rubber U, it becomes possible to improve the heat resistance performance and the rolling resistance performance of the tread portion 2. Further, by providing the sipe 6 on the groove wall 3b of the circumferential main groove 3, it is possible to improve the uneven wear resistance performance of the tread portion 2.

  In such a heavy-duty pneumatic tire 1, in this embodiment, the sipe 6 is provided in the region of the cap tread rubber C, and the sipe 6 with respect to the groove depth D of the circumferential main groove 3 on the inner side in the tire radial direction from the tread surface 2 a. The groove width W of the sipe 6 in the tire width direction from the groove wall 3b of the circumferential main groove 3 to the land portion 4 side is set to a range of 0.5 ≦ d / D ≦ 1.0. It is formed so as to gradually decrease from the tread surface 2a toward the inner side in the tire radial direction.

  According to the heavy duty pneumatic tire 1, the groove depth d of the sipe 6 is set to 50 [%] or more of the groove depth D of the circumferential main groove 3, so that it is from the middle of wear, that is, from the tread surface 2a. Even when the tread portion 2 is worn 50% or more of the groove depth D of the circumferential main groove 3 on the inner side in the tire radial direction, it is possible to obtain the effect of improving the uneven wear resistance performance by the sipe 6. . Moreover, according to the heavy-duty pneumatic tire 1, the sipe 6 is provided in the region of the cap tread rubber C, and the groove width W of the sipe 6 is gradually reduced from the tread surface 2a toward the inside in the tire radial direction. Since the sipe 6 is arranged so as to be away from the undertread rubber U, even when the undertread rubber U is exposed on the surface of the tread portion 2 after the middle stage of wear, the cut chipping starting from the sipe 6 is performed. Occurrence can be suppressed.

  Note that the cut chipping is performed in the center region of the tire that receives the most load (from 40 [%] to 60 [%] of the distance between the tire equatorial plane CL and the ground contact edge T on the outer side in the tire width direction from the tire equatorial plane CL. Range). Therefore, the sipe described above at least in the range of the center region (in this embodiment, both the groove walls of the central circumferential main groove 3 and the groove walls on the tire width direction inside of the circumferential main grooves 3 on both sides in the tire width direction). With the configuration of 6, it is possible to obtain the effect of improving the cut chipping resistance.

  Further, in the heavy duty pneumatic tire 1 of the present embodiment, as shown in FIG. 2, the sipe 6 is formed so that the groove width WA at the tread surface 2a is 2 mm or more and 5 mm or less. preferable.

  According to the heavy duty pneumatic tire 1, the groove width WA of the sipe 6 on the tread surface 2a is the maximum groove width of the sipe 6, and the groove width WA is set to 5 mm or less. Since the groove width W is gradually reduced, the sipe 6 can be reliably moved away from the undertread rubber U, so that the effect of improving the cut chipping resistance can be remarkably obtained. Further, by setting the groove width WA of the sipe 6 on the tread surface 2a to be 2 [mm] or more, the uneven wear resistance performance by the sipe 6 can be remarkably obtained. Note that the groove width WA of the sipe 6 on the tread surface 2a is 2.5 [mm] or more and 5 [mm] in order to obtain the improvement effect of the anti-cut chipping performance and the uneven wear resistance improvement effect by the sipe 6. The following is more preferable.

  Further, as shown in FIG. 2, in the heavy load pneumatic tire 1 of the present embodiment, the sipe 6 has a groove width WB at 50 [%] of the groove depth D of the circumferential main groove 3 on the tread surface 2 a. The groove width WA is preferably 60% or less of the groove width WA.

  According to this heavy duty pneumatic tire 1, the groove width W of the sipe 6 at the tread surface 2a is equal to or greater than 50 [%] of the groove depth D of the circumferential main groove 3 after the middle wear period when the tread portion 2 is worn. Since the groove 6 is gradually reduced to 60% or less of the groove width WA, the sipe 6 can be surely moved away from the undertread rubber U, so that the effect of improving the cut chipping resistance can be remarkably obtained. .

  In addition, as shown in FIG. 2, the heavy tread pneumatic tire 1 of the present embodiment is such that the undertread rubber U has a tire radial direction from 50% of the groove depth D of the circumferential main groove 3 in the land portion 4. It is preferable to arrange in the inner range.

  It is desirable to set the groove width W of the sipe 6 appropriately in order to obtain the uneven wear resistance performance by the sipe 6, and to reduce the groove width W of the sipe 6 in order to obtain the cut chipping performance. It is desirable to keep away from the under tread rubber U. For this reason, by arranging the under tread rubber U in the range from 50 [%] of the groove depth D of the circumferential main groove 3 in the land portion 4 to the inner side in the tire radial direction, before the middle period of wear, The uneven wear resistance by the sipe 6 having an appropriate groove width W is suppressed by suppressing the exposure to the surface of the tread portion 2, and the resistance by the sipe 6 having the groove width W reduced after the middle period of wear. Cut chipping performance can be obtained remarkably.

  In the heavy load pneumatic tire 1 of the present embodiment, the loss tangent tan δC of the cap tread rubber C at 60 ° C. and the loss tangent tan δU of the undertread rubber U at 60 ° C. satisfy the relationship of tan δU <tan δC. preferable.

  According to the heavy-duty pneumatic tire 1, in the tread portion 2, the tread surface 2 a is a cap tread rubber C made of an abrasion-resistant rubber layer, and the inner side in the tire radial direction of the cap tread rubber C is made of a low heat-generating rubber layer. The effect of improving the heat resistance performance and rolling resistance performance of the tread portion 2 due to the under-tread rubber U can be remarkably obtained.

  Further, as shown in FIG. 2, the heavy-duty pneumatic tire 1 of the present embodiment has the shortest distance H at the position of the shortest distance H between the end of the sipe 6 and the undertread rubber U in the tire width direction. It is preferable that the groove width is WC or more.

  That is, it is preferable that the shortest distance H is equal to or greater than the groove width WC of the sipe 6 at a position where the sipe 6 and the undertread rubber U are closest to each other in the tire width direction. According to this heavy load pneumatic tire 1, since the under tread rubber U is separated from the sipe 6 by the groove width WC of the sipe 6, the effect of improving the cut chipping resistance can be obtained remarkably.

  FIG. 8 is a chart showing the results of the performance test of the heavy duty pneumatic tire according to this example. In this example, performance tests on cut chipping resistance and uneven wear resistance were performed on a plurality of types of heavy-duty pneumatic tires having different conditions.

  In this performance test, a heavy-duty pneumatic tire having a tire size of 11R22.516 was assembled on a regular rim, filled with a regular internal pressure, and mounted on a 2-DD test vehicle.

  The evaluation method of cut chipping resistance was determined by visual inspection of the degree of cut chipping of the tread portion after running 50,000 [km] on the test vehicle. Then, based on this determination result, index evaluation with the conventional example as a reference (100) is performed. This evaluation shows that the larger the index, the more the cut chipping is reduced and the cut chipping resistance is excellent.

  The evaluation method of the wear resistance performance was determined by visual observation of the occurrence of uneven wear on the land after running 50,000 [km] at an average speed of 60 [km / h] on the test vehicle.

  As shown in FIG. 8, in the conventional heavy-duty pneumatic tire, the sipe groove depth d with respect to the groove depth D of the main groove on the inner side in the tire radial direction from the tread surface is set to 0.5. The groove width is formed uniformly from the tread surface toward the inside in the tire radial direction. The pneumatic tire for heavy load of the comparative example is formed by gradually decreasing the groove width of the sipe from the tread surface toward the inner side in the tire radial direction, but the groove depth D of the main groove on the inner side in the tire radial direction from the tread surface. The groove depth d of the sipe with respect to is 0.47.

  On the other hand, as shown in FIG. 8, the heavy duty pneumatic tires of Examples 1 to 11 have a sipe groove depth d of 0.5 with respect to the groove depth D of the main groove on the inner side in the tire radial direction from the tread surface. The groove width of the sipe is formed to gradually decrease from the tread surface toward the inner side in the tire radial direction. In the heavy duty pneumatic tires of Examples 4 to 11, the groove width WA of the sipe on the tread surface is set to 5 [mm] or less. In the heavy-duty pneumatic tires of Examples 7 to 11, the sipe groove width WB at 50 [%] of the groove depth D of the main groove is formed to be 60 [%] or less of the groove width WA at the tread surface. doing. In the heavy-duty pneumatic tire of Example 11, the shortest distance from the sipe of the undertread rubber is equal to or greater than the sipe groove width.

  As shown in the test results of FIG. 8, it can be seen that the heavy duty pneumatic tires of Examples 1 to 11 have improved cut chipping resistance and maintained uneven wear resistance.

1 Pneumatic tire for heavy loads 2 Tread part 2a Tread surface 3 Circumferential main groove (main groove)
3a groove bottom 3b groove wall 4 land 6 sipe C cap tread rubber U under tread rubber

Claims (6)

A cap tread rubber disposed on a tread surface having a plurality of land portions extending in the tire circumferential direction by a plurality of main grooves extending along the tire circumferential direction, and provided inside the tire tread rubber in the tire radial direction. The tread portion is configured with the under tread rubber disposed on the outer side in the tire radial direction from the groove bottom of the main groove at the land portion on the side portion of the main groove, and the groove wall of the main groove and the tread In a heavy duty pneumatic tire having a sipe that opens in a plane and terminates in the land portion on the side of the main groove,
The sipe is provided in a region of the cap tread rubber, and the groove depth d of the sipe with respect to the groove depth D of the main groove on the inner side in the tire radial direction from the tread surface is 0.5 ≦ d / D ≦ 1.0. The groove width of the sipe in the tire width direction from the groove wall of the main groove to the land portion side is gradually reduced from the tread surface toward the inner side in the tire radial direction. Heavy duty pneumatic tire.   2. The heavy-duty pneumatic tire according to claim 1, wherein the sipe is formed so that a groove width on the tread surface is 2 mm or more and 5 mm or less.   The sipe is formed so that a groove width at 50% of the groove depth D of the main groove is 60% or less of a groove width on the tread surface. The heavy-duty pneumatic tire described.   The undertread rubber is arranged in a range in the tire radial direction inner side from 50 [%] of the groove depth D of the main groove in the land portion. The heavy-duty pneumatic tire described.   5. The loss tangent tan δC of the cap tread rubber at 60 ° C. and the loss tangent tan δU of the undertread rubber at 60 ° C. satisfy the relationship of tan δU <tan δC. The heavy-duty pneumatic tire described.   6. The shortest distance between the end of the sipe and the under tread rubber in the tire width direction is equal to or greater than the groove width of the sipe. Heavy duty pneumatic tires.

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