JP7701600B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire suitable for heavy loads used on trucks, buses, etc., and more specifically, to a pneumatic tire that can effectively prevent toe chipping in the bead portion.

In some heavy-duty pneumatic tires used on trucks, buses, etc., a carcass layer is mounted between a pair of bead sections, the carcass layer is wrapped around the bead core of each bead section from the inside to the outside of the tire, and a steel reinforcing layer containing multiple steel cords is arranged in each bead section so as to encase the carcass layer. With this type of pneumatic tire, there is a problem in that the frequency of toe chipping occurring in the bead section during tire reassembly is relatively high.

In a pneumatic tire constructed as described above, when multiple organic fiber reinforcement layers are arranged on the outer side of the steel reinforcement layer in the tire width direction and these organic fiber reinforcement layers are cross-laminated even under the bead core (see, for example, Patent Document 1), the flow of rubber from the bead heel during vulcanization is suppressed, making it possible to arrange the bead core on the toe side and making the angle formed by the toe obtuse. Therefore, in a structure in which an organic fiber reinforcement layer is added to the bead portion, the problem of toe chipping is reduced. However, even in a structure in which an organic fiber reinforcement layer is added to the bead portion, toe chipping still occurs, and further improvement is required.

Patent No. 6554957

The object of the present invention is to provide a pneumatic tire that can effectively prevent toe chipping in the bead portion.

In order to achieve the above object, a pneumatic tire of the present invention includes a tread portion extending in a circumferential direction of the tire to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side of the sidewall portions in the outer radial direction of the tire, a carcass layer is fitted between the pair of bead portions, the carcass layer is wound up around the bead cores of each bead portion from the inner side to the outer side of the tire, and a steel reinforcing layer including a plurality of steel cords is disposed in each bead portion so as to encase the carcass layer,
Two organic fiber reinforcement layers are disposed on the outer side of the steel reinforcement layer in the tire width direction, and the two organic fiber reinforcement layers include an inner organic fiber reinforcement layer adjacent to the steel reinforcement layer and an outer organic fiber reinforcement layer located on the outer side of the inner organic fiber reinforcement layer in the tire width direction,
an inner diameter side end portion of the inner organic fiber reinforcement layer is located inward in the tire width direction with respect to a line segment formed from a normal line drawn from a vertex that protrudes most inward in the tire radial direction of the bead core to a surface of the bead base,
the outer organic fiber reinforcement layer is disposed so as to cover an inner diameter side end portion of the inner organic fiber reinforcement layer, the inner diameter side end portion of the outer organic fiber reinforcement layer is spaced 5 mm or more from the inner diameter side end portion of the inner organic fiber reinforcement layer, and is located radially inward in the tire radial direction of a line segment consisting of a horizontal line drawn in the tire width direction from an outer end portion in the tire width direction of the steel reinforcement layer ,
The inner organic fiber reinforcement layer includes a plain weave material made of warp and weft yarns, and the fiber structure of the warp and weft yarns of the plain weave material is in the range of 200 dtex/1 to 1000 dtex/1 .

As a result of extensive research into tire structures in which an organic fiber reinforcement layer is arranged in the bead section, the inventor discovered that most cracks caused by toe chipping propagate to the ends of the organic fiber reinforcement layer, and that this phenomenon is caused by the ends of the organic fiber reinforcement layer being in contact with the rubber in the area near the toe of the bead section without being covered by other reinforcing layers, which led to the invention.

That is, in the present invention, both the inner organic fiber reinforcement layer and the outer organic fiber reinforcement layer are extended at least to under the bead core, based on the line segment consisting of the normal drawn from the apex that protrudes most inward in the tire radial direction of the bead core to the bead base surface, so that the rubber flow of the bead portion during vulcanization is suppressed, the position of the bead core is closer to the toe side, and the angle formed by the toe of the bead portion can be increased and made obtuse. As a result, the rigidity of the toe of the bead portion is increased and toe chipping is less likely to occur. In addition, the outer organic fiber reinforcement layer is arranged to cover the inner diameter side end of the inner organic fiber reinforcement layer, and the inner diameter side end of the outer organic fiber reinforcement layer is 5 mm or more away from the inner diameter side end of the inner organic fiber reinforcement layer, so that even if the toe of the bead portion is deformed when the rim is removed, cracks starting from the inner diameter side end of the outer organic fiber reinforcement layer and the inner diameter side end of the inner organic fiber reinforcement layer are less likely to occur. As a result, the toe chipping resistance can be significantly improved.

In the present invention, it is preferable that the inner organic fiber reinforcement layer includes a plain weave material consisting of warp and weft yarns, and the fiber structure of the warp and weft yarns of the plain weave material is in the range of 200 dtex/1 to 1000 dtex/1. By thinning the warp and weft yarns of the plain weave material constituting the inner organic fiber reinforcement layer in this way, the step portion generated when the outer organic fiber reinforcement layer is arranged to cover the inner diameter side end of the inner organic fiber reinforcement layer is reduced, stress concentration at the step portion is reduced, and toe chipping can be effectively suppressed. In addition, the necessary minimum thickness is ensured for the warp and weft yarns of the plain weave material constituting the inner organic fiber reinforcement layer, so that the effect of suppressing rubber flow can also be exhibited.

The distance A from the apex protruding most outward in the width direction of the bead core, measured along a straight line parallel to the longest side of the bead core, to the bead heel position is preferably in the range of 2.5 mm to 5.5 mm. By ensuring sufficient distance A in this way, the position of the bead core is shifted toward the toe side, and the angle formed by the toe of the bead portion can be increased. As a result, the rigidity of the toe of the bead portion is increased, making it less likely for the toe to chip.

1 is a meridian cross-sectional view showing a heavy-duty pneumatic tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a bead portion of the pneumatic tire of FIG. 1 . 2 is another cross-sectional view showing the bead portion of the pneumatic tire of FIG. 1 . FIG. 1 is a cross-sectional view showing a bead portion of a conventional pneumatic tire (without an organic fiber reinforcement layer). FIG. 11 is a cross-sectional view showing a bead portion of another conventional pneumatic tire (with an organic fiber reinforcement layer).

The configuration of the present invention will be described in detail below with reference to the attached drawings. Figure 1 shows a heavy-duty pneumatic tire according to an embodiment of the present invention, and Figures 2 and 3 show the main parts of the tire.

As shown in FIG. 1, the pneumatic tire of this embodiment has a tread portion 1 that extends in the circumferential direction of the tire and forms an annular shape, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged on the radially inner side of the sidewall portions 2.

A carcass layer 4 is mounted between a pair of bead portions 3, 3. This carcass layer 4 includes multiple steel cords extending in the tire radial direction, and has a structure in which it is wound from the inside to the outside of the tire around a bead core 5 arranged in each bead portion 3. A bead filler 6 made of a rubber composition with a triangular cross section is arranged on the outer periphery of the bead core 5.

Four belt layers 7 are embedded on the outer diameter side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes multiple belt cords (steel cords) that are inclined with respect to the tire circumferential direction. These belt layers 7 include two central main belt layers 72, 73 in which the belt cords cross each other, and auxiliary belt layers 71, 74 arranged on the inner diameter side and outer diameter side of these main belt layers 72, 73. The inclination angle of the belt cords that make up the main belt layers 72, 73 with respect to the tire circumferential direction is set in the range of 15° to 35°, for example, and the inclination angle of the belt cords that make up the auxiliary belt layers 71, 74 with respect to the tire circumferential direction is set in the range of 15° to 75°, for example.

In the above pneumatic tire, a steel reinforcement layer 10 including multiple steel cords is arranged in each bead portion 3 so as to envelop the carcass layer 4, the bead core 5, and the bead filler 6. Two organic fiber reinforcement layers 11, 12 are arranged on the outer side of the steel reinforcement layer 10 in the tire width direction. The inner organic fiber reinforcement layer 11 is adjacent to the steel reinforcement layer 10, and the outer organic fiber reinforcement layer 12 is located further outboard in the tire width direction than the inner organic fiber reinforcement layer 11. Each of these organic fiber reinforcement layers 11, 12 may include multiple organic fiber cords aligned in one direction, or may include a plain weave material.

As shown in FIG. 2, the inner diameter side end 11i of the inner organic fiber reinforcement layer 11 is located in the tire width direction inside the line segment J formed by a normal line drawn from the apex that protrudes most inward in the tire radial direction of the bead core 5 to the surface of the bead base 3b. In other words, the inner organic fiber reinforcement layer 11 extends to below the bead core 5. The inner diameter side end 11i of the inner organic fiber reinforcement layer 11 is located near the toe 3t formed at the tip of the bead portion 3.

On the other hand, the outer organic fiber reinforcement layer 12 is arranged to cover the inner diameter side end 11i of the inner organic fiber reinforcement layer 11. In other words, the inner diameter side end 12i of the outer organic fiber reinforcement layer 12 is located inward in the tire width direction than the inner diameter side end 11i of the inner organic fiber reinforcement layer 11. The inner diameter side end 12i of the outer organic fiber reinforcement layer 12 is 5 mm or more away from the inner diameter side end 11i of the inner organic fiber reinforcement layer 11, and is located inward in the tire radial direction than the line segment L consisting of a horizontal line drawn in the tire width direction from the outer end 10e of the steel reinforcement layer 10 in the tire width direction. The distance between the inner diameter side end 12i of the outer organic fiber reinforcement layer 12 and the inner diameter side end 11i of the inner organic fiber reinforcement layer 11 is a distance measured along the steel reinforcement layer 10. In addition, the horizontal line for identifying the line segment L is identified when the tire is unloaded by itself.

In the above-described pneumatic tire, both the inner organic fiber reinforcement layer 11 and the outer organic fiber reinforcement layer 12 extend at least to below the bead core 5, based on the line segment J formed by the normal line drawn from the apex that protrudes most radially inward of the bead core 5 to the surface of the bead base 3b. This suppresses the flow of rubber in the bead portion 3 during vulcanization, moves the position of the bead core 5 toward the toe 3t, and increases the angle θ formed by the toe 3t of the bead portion 3, making it possible to make it obtuse. As a result, the rigidity of the toe 3t of the bead portion 3 increases, making it less likely for the toe to chip.

In addition, the outer organic fiber reinforcement layer 12 is arranged to cover the inner diameter end 11i of the inner organic fiber reinforcement layer 11, and the inner diameter end 12i of the outer organic fiber reinforcement layer 12 is at least 5 mm away from the inner diameter end 11i of the inner organic fiber reinforcement layer 11. Therefore, even if the toe 3t of the bead portion 3 is deformed when the rim is removed, cracks are unlikely to occur starting from the inner diameter end 12i of the outer organic fiber reinforcement layer 12 and the inner diameter end 11i of the inner organic fiber reinforcement layer 11. As a result, the toe chipping resistance can be significantly improved.

Here, if the distance between the inner diameter end 12i of the outer organic fiber reinforcement layer 12 and the inner diameter end 11i of the inner organic fiber reinforcement layer 11 is less than 5 mm, the inner diameter end 12i of the outer organic fiber reinforcement layer 12 is located near the toe 3t of the bead portion 3, so that cracks starting from the inner diameter end 12i of the outer organic fiber reinforcement layer 12 are likely to occur, and toe chipping is likely to occur. In addition, the region R on the inner side in the tire radial direction of the line segment L consisting of a horizontal line drawn in the tire width direction from the outer end 10e of the steel reinforcement layer 10 on the tire width direction is an area with little movement when the tire rolls, but if the inner diameter end 12i of the outer organic fiber reinforcement layer 12 is located on the outer side in the tire radial direction of the line segment L, the movement during tire rolling is large, and separation is likely to occur from the inner diameter end 12i of the outer organic fiber reinforcement layer 12.

In the above pneumatic tire, the inner organic fiber reinforcement layer 11 includes a plurality of organic fiber cords aligned in one direction, and the fiber structure of the organic fiber cords is preferably in the range of 800 dtex/2 to 1500 dtex/2. By thinning the organic fiber cords constituting the inner organic fiber reinforcement layer 11 in this way, the step that occurs when the outer organic fiber reinforcement layer 12 is arranged to cover the inner diameter side end 11i of the inner organic fiber reinforcement layer 11 is made smaller, stress concentration at the step is reduced, and toe chipping can be effectively suppressed. In addition, the organic fiber cords constituting the inner organic fiber reinforcement layer 11 are ensured to have the minimum necessary thickness, which also has the effect of suppressing rubber flow.

Here, if the fiber structure of the organic fiber cord is smaller than 800 dtex/2, the rubber flow in the bead portion 3 cannot be suppressed, and conversely, if it is larger than 1500 dtex/2, the step that occurs when the outer organic fiber reinforcement layer 12 is arranged to cover the inner diameter side end portion 11i of the inner organic fiber reinforcement layer 11 becomes large, and the effect of suppressing toe chipping decreases due to stress concentration at the step. Note that when the inner organic fiber reinforcement layer 11 includes a reinforcing material made of multiple organic fiber cords aligned in one direction, the reinforcing material of the outer organic fiber reinforcement layer 12 may be multiple organic fiber cords aligned in one direction, or it may be a plain weave material made of warp and weft threads.

In another embodiment of the pneumatic tire, the inner organic fiber reinforcement layer 11 includes a plain weave material made of warp and weft yarns, and the fiber structure of the warp and weft yarns of the plain weave material is preferably in the range of 200 dtex/1 to 1000 dtex/1. By thinning the warp and weft yarns of the plain weave material that constitutes the inner organic fiber reinforcement layer 11 in this way, the step that occurs when the outer organic fiber reinforcement layer 12 is arranged to cover the inner diameter side end 11i of the inner organic fiber reinforcement layer 11 is reduced, stress concentration at the step is reduced, and toe chipping can be effectively suppressed. In addition, the minimum necessary thickness is ensured for the warp and weft yarns of the plain weave material that constitutes the inner organic fiber reinforcement layer 11, so that the effect of suppressing rubber flow can also be achieved.

Here, if the fiber structure of the warp and weft threads of the plain weave material is smaller than 200 dtex/1, the rubber flow in the bead portion 3 cannot be suppressed, and conversely, if it is larger than 1000 dtex/1, the step that occurs when the outer organic fiber reinforcement layer 12 is arranged to cover the inner diameter side end portion 11i of the inner organic fiber reinforcement layer 11 becomes large, and the effect of suppressing toe chipping decreases due to stress concentration at the step. Note that when the inner organic fiber reinforcement layer 11 includes a reinforcing material made of a plain weave material including warp and weft threads, the reinforcing material of the outer organic fiber reinforcement layer 12 may be a plurality of organic fiber cords aligned in one direction, or it may be a plain weave material made of warp and weft threads.

As shown in FIG. 3, in the above pneumatic tire, the distance A from the apex E protruding most outward in the width direction of the bead core 5 to the bead heel position, measured along a straight line D that passes through the apex E and is parallel to the longest side of the bead core 5, is preferably in the range of 2.5 mm to 5.5 mm. By ensuring a sufficient distance A in this way, the position of the bead core 5 is closer to the toe 3t of the bead portion 3, and the angle θ formed by the toe 3t of the bead portion 3 can be increased. As a result, the rigidity of the toe 3t of the bead portion 3 is increased, making it less likely that toe chipping will occur.

The specific method for calculating distance A is as follows. The bead core 5 has a laminated structure in which multiple wires are arranged in the tire meridian cross section. The vertex E is the point where a straight line D that passes through the center of gravity of the wire located at the outermost side of the bead core 5 in the width direction and is parallel to the longest side of the bead core 5 intersects with the outline of the wire located at the outermost side in the width direction. Here, when a straight line D that passes through the vertex E that protrudes most outward in the width direction of the bead core 5 and is parallel to the longest side of the bead core 5 intersects with an extension of the side that forms the profile of the bead bottom surface and an extension of the curve that forms the profile of the bead back surface, a straight line M that passes through the imaginary intersection point H and is perpendicular to the straight line D, and a straight line F that passes through the vertex E and is perpendicular to the straight line D are calculated, distance A is the length of the line segment on the straight line D that is partitioned between the straight line M and the straight line F.

If the distance A is less than 2.5 mm, the position of the bead core 5 is not close enough to the toe 3t side, and the increase in the rigidity of the toe 3t is small, reducing the effect of preventing toe chipping. Conversely, if the distance A is more than 5.5 mm, this will result in an excessive increase in costs.

Figure 4 shows the bead portion of a conventional pneumatic tire (without an organic fiber reinforcement layer), and Figure 5 shows the bead portion of another conventional pneumatic tire (with an organic fiber reinforcement layer). As shown in Figure 4, if the organic fiber reinforcement layers 11, 12 are not arranged in the bead portion 3, rubber flow occurs in the bead portion 3 during vulcanization, and the bead core 5 is located on the bead heel side, so the angle θ formed by the toe 3t of the bead portion 3 becomes small. Therefore, toe chipping is likely to occur in the bead portion 3. On the other hand, as shown in Figure 5, if the organic fiber reinforcement layers 11, 12 are arranged in the bead portion 3, but the inner diameter side end 12i of the outer organic fiber reinforcement layer 12 is located near the toe 3t of the bead portion 3 and the inner diameter side end 12i is not covered by another reinforcement layer, cracks starting from the inner diameter side end 12i of the outer organic fiber reinforcement layer 12 are less likely to occur, and toe chipping resistance cannot be sufficiently improved. The pneumatic tire according to the embodiment of the present invention described above can solve these problems and effectively prevent toe chipping in the bead portion.

The pneumatic tire according to the above-mentioned embodiment preferably has a load index of 121 or more on a single wheel, or a ply rating of 10PR or more. Pneumatic tires having such load indexes or ply ratings are generally heavy-duty tires. The present invention is expected to be of significant effect in heavy-duty pneumatic tires.

In a pneumatic tire having a tire size of 275/70R22.5, which is provided with a tread portion, a pair of sidewall portions, and a pair of bead portions, a carcass layer including a plurality of steel cords is mounted between the pair of bead portions, the carcass layer is wound up around the bead core of each bead portion from the inside to the outside of the tire, and a steel reinforcing layer including a plurality of steel cords is disposed in each bead portion so as to encase the carcass layer, tires of Conventional Examples 1 to 4, Comparative Examples 1 and 2, and Examples 1 to 7 were manufactured, which differ only in the structure of the bead portions. Note that in this specification, Examples 1, 2, and 4 to 7 are reference examples.

For the tires of Conventional Examples 1 to 4, Comparative Examples 1 and 2, and Examples 1 to 7, the presence or absence of an organic fiber reinforcement layer, the type of the inner organic fiber reinforcement layer, the fiber structure of the inner organic fiber reinforcement layer, the position of the inner diameter side end of the inner fiber reinforcement layer, the type of the outer organic fiber reinforcement layer, the fiber structure of the outer organic fiber reinforcement layer, the position of the inner diameter side end of the outer fiber reinforcement layer, the presence or absence of covering the inner diameter side end of the inner fiber reinforcement layer with the outer organic fiber reinforcement layer, the distance between the inner diameter side end of the outer organic fiber reinforcement layer and the inner diameter side end of the inner organic fiber reinforcement layer, the bead core distance A, and the toe angle θ were set as shown in Table 1.

Regarding the types of the inner organic fiber reinforcement layer and the outer organic fiber reinforcement layer, if the reinforcing material is multiple organic fiber cords aligned in one direction, it is called "blind weave", and if the reinforcing material is a plain weave material consisting of warp and weft threads, it is called "plain weave". Regarding the position of the inner diameter side end of the inner organic fiber reinforcement layer, if the inner diameter side end is located inside the line segment J in the tire width direction, it is called "inner side", and if the inner diameter side end is located outside the line segment J in the tire width direction, it is called "outer side". Regarding the position of the inner diameter side end of the outer organic fiber reinforcement layer, if the inner diameter side end is located inside the line segment L in the tire radial direction, it is called "lower side", and if the inner diameter side end is located outside the line segment L in the tire radial direction, it is called "upper side".

These test tires were evaluated for separation resistance (organic fiber reinforcement layer, carcass layer) and toe chipping resistance using the following test methods, and the results are shown in Table 1.

Separation resistance (organic fiber reinforcement layer, carcass layer):
Each test tire was mounted on a JATMA-specified rim, and a running test was performed using a drum test machine under the conditions of 75% of the JATMA-specified air pressure, 1.4 times the JATMA-specified load, and a running speed of 49 km/h. After running 40,000 km, the test tire was cut along the tire meridian at eight points equally spaced in the tire circumferential direction, and the cross-sectional lengths of cracks starting from the inner diameter side end of the outer organic fiber reinforcement layer and the rolled-up end of the carcass layer were measured at the eight cut surfaces (total of 16 points) of both bead portions. Then, the sum of the cross-sectional lengths of cracks starting from the inner diameter side end of the outer organic fiber reinforcement layer and the rolled-up end of the carcass layer was calculated. The evaluation results were expressed as an index using the reciprocal of the measured value, with Conventional Example 3 being 100 for each of the organic fiber reinforcement layer and the carcass layer. The larger the index value, the better the separation resistance.

Toe chipping resistance:
Each test tire was mounted on a JATMA-specified rim, and a running test was performed using a drum test machine under conditions of 75% of the JATMA-specified air pressure, 1.4 times the JATMA-specified load, and a running speed of 49 km/h. After running 40,000 km, the test tire was repeatedly removed from the rim and mounted, and the number of times it was removed and mounted when toe chipping first occurred was counted. The evaluation results were expressed as an index, with the number of times that the conventional example 1 was removed and mounted when toe chipping occurred being set to 100. The higher the index value, the better the toe chipping resistance.

As can be seen from Table 1, the tires of Examples 1 to 7 had significantly improved toe chip resistance compared to Conventional Examples 1 to 4, and separation resistance was sufficiently ensured. Conventional Example 1 tire did not have an organic fiber reinforcement layer, so the carcass line was not balanced due to the flow of rubber during vulcanization, and as a result, cracks were likely to occur at the wound-up end of the carcass layer. In Comparative Example 1 tire, the distance between the inner diameter side end of the outer organic fiber reinforcement layer and the inner diameter side end of the inner organic fiber reinforcement layer was too small, so the effect of improving toe chip resistance was insufficient. In Comparative Example 2 tire, the inner diameter side end of the outer organic fiber reinforcement layer was located radially outboard of the line segment L, so cracks were likely to occur starting from the inner diameter side end of the outer organic fiber reinforcement layer.

REFERENCE SIGNS LIST 1 tread portion 2 sidewall portion 3 bead portion 3t toe 3b bead base 4 carcass layer 5 bead core 6 bead filler 7 belt layer 10 steel reinforcing layer 10e end portion 11 inner organic fiber reinforcing layer 11i inner diameter side end portion 12 outer organic fiber reinforcing layer 12i inner diameter side end portion

Claims (2)

A pneumatic tire comprising a tread portion extending in a circumferential direction of the tire and forming an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side of the sidewall portions in the outer radial direction of the tire, a carcass layer being fitted between the pair of bead portions, the carcass layer being wound up around a bead core of each bead portion from the inner side to the outer side of the tire, and a steel reinforcing layer including a plurality of steel cords being disposed in each bead portion so as to encase the carcass layer,
Two organic fiber reinforcement layers are disposed on the outer side of the steel reinforcement layer in the tire width direction, and the two organic fiber reinforcement layers include an inner organic fiber reinforcement layer adjacent to the steel reinforcement layer and an outer organic fiber reinforcement layer located on the outer side of the inner organic fiber reinforcement layer in the tire width direction,
an inner diameter side end portion of the inner organic fiber reinforcement layer is located inward in the tire width direction with respect to a line segment formed from a normal line drawn from a vertex that protrudes most inward in the tire radial direction of the bead core to a surface of the bead base,
the outer organic fiber reinforcement layer is disposed so as to cover an inner diameter side end portion of the inner organic fiber reinforcement layer, the inner diameter side end portion of the outer organic fiber reinforcement layer is spaced 5 mm or more from the inner diameter side end portion of the inner organic fiber reinforcement layer, and is located radially inward in the tire radial direction of a line segment consisting of a horizontal line drawn in the tire width direction from an outer end portion in the tire width direction of the steel reinforcement layer ,
The pneumatic tire is characterized in that the inner organic fiber reinforcing layer includes a plain weave material made of warp yarns and weft yarns, and the fiber structure of the warp yarns and weft yarns of the plain weave material is in the range of 200 dtex/1 to 1000 dtex/1 . 2. The pneumatic tire according to claim 1, wherein a distance A from the apex protruding most outward in the width direction of the bead core to a bead heel position, which is measured along a straight line passing through the apex and parallel to the longest side of the bead core, is in a range of 2.5 mm to 5.5 mm.

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