JP4732776B2 - Pneumatic tires for motorcycles - Google Patents

Description

  The present invention relates to a manufacturing method for a pneumatic tire for a motorcycle, and more particularly, to a pneumatic tire for a motorcycle mainly for traveling on rough terrain.

  Among so-called motocross tires mainly intended for use on rough terrain including muddy grounds among motorcycle pneumatic tires, a plurality of blocks are formed on the tread.

  For this type of vulcanization molding of pneumatic tires for motorcycles, it is common to use a so-called full mold consisting of a pair of one lower mold in the tire width direction and another upper mold on the other side of the tire equatorial plane. Met.

  However, the full mold may cause problems such as mold biting, and the pneumatic tire for a motorcycle may be vulcanized by a so-called split mold.

  In addition, as a split mold, there exists a thing disclosed by patent document 1, for example (The thing disclosed by patent document 1 is a thing which vulcanizes-molds the pneumatic tire for four-wheeled vehicles, As a structure, The one for motorcycles has the same structure.)

  FIG. 3 is a cross-sectional view showing a schematic configuration of a pneumatic tire 112 for a motorcycle that is molded by a conventional split mold 110.

  As shown in FIG. 3, the split mold 110 is movable in the lower side mold 114, the upper side mold 116 that can be raised and lowered (in the direction of arrow A in FIG. 3), and in the radial direction (in the direction of arrow B in FIG. 3). And a sector mold 118 composed of a plurality of segments 118A.

  In FIG. 3, reference numeral 120 denotes a tread portion of the pneumatic tire 112 for a motorcycle, reference numeral 122 denotes a block formed on the tread portion 120, reference numeral 124 denotes a groove bottom, reference numeral BL denotes a bead base line, reference numeral TW denotes a tread width, Symbol SH is a section height (section height), symbol SW is a tire width, symbol WH is a tire width height, symbol S is a contact end of the tread portion 120, symbol DH is a drop height, symbol W is a split position height, Reference symbol P denotes a block root outside the tire width direction in the outermost block (shoulder block) in the tire width direction (contact point between the block outer wall surface 122a outside the tire width direction and the sidewall surface (in FIG. 3, the center of curvature is inside the tire). Intersection of the side wall arc having the center of curvature and the arc of the block outer wall surface 122a having the center of curvature outside the tire (inflection point)) Reference symbol T is a block root height, reference symbol D is a rim diameter, reference symbol θ is an angle formed by a block outer wall surface 122a on the outer side in the tire width direction of the outermost block 122 in the tire width direction and the tire radial direction, and reference symbol h is a block height. The symbol PL indicates the split positions of the sector mold 118, the lower side mold 114, and the upper side mold 116, respectively.

  However, in a motocross tire having a block height h of 10 mm or more, when the split position PL of the sector mold 118, the lower side mold 114, and the upper side mold 116 is set near the ground contact end S of the tread portion 120, the outermost side The block row is formed by the sector mold 118, the lower side mold 114, and the upper side mold 116.

  For this reason, on the block outer wall surface 122a of the outermost block row of the vulcanized molded tire, it extends in the tire circumferential direction to a position facing the split position of the sector mold 118, the lower side mold 114, and the upper side mold 116. As shown in FIG. 4 and FIG. 5, there is a problem that the side wall surface of the block becomes discontinuous (the portion indicated by the arrow A) due to the formation of the split position equivalent line and the mold misalignment, etc. .

  In order to use the split mold and not cause the above problem, it is necessary to set the split position PL between the side mold and the sector mold near the position of the maximum tire width (SW) of the mold.

  However, when increasing the tire contact area and falling height DH to improve handling stability, the so-called Tr curvature ratio (falling height DH / tread width TW) increases, and the outermost block in the tire width direction As a result of the row approaching the bead portion (inner side in the tire radial direction), the mold split position PL has to be set to an intermediate position of the outer wall surface 122a on the outer side in the tire width direction of the outermost block row in the tire width direction. There is a problem that the side wall surface becomes discontinuous and the base point of crack generation is created.

  Further, in the conventional vulcanizer, when a conventional mold having a split position PL on the inner side in the tire radial direction from the block root P is used, there is a problem that the opening amount of the sector mold to the outer side in the radial direction is limited.

  In recent years, in a motocross tire whose drop height DH is increasing, the block root P of the outermost block row inevitably moves inward in the tire radial direction, and as a result, the block root height T is also decreased.

  Therefore, even if the sector mold opens radially outward after vulcanization molding, the diameter of the mold split position PL (inner diameter of the sector mold) does not become larger than the outer diameter of the product tire, and the sector mold and the product tire interfere with each other. As a result, it becomes difficult to take out the product tire, or it becomes impossible to take out in some cases.

  Further, in the case of a radial tire using a so-called spiral belt in which a high elastic cord such as an aramid fiber is spirally wound around the outer periphery of the carcass on the belt, the increase in the diameter of the tread portion during vulcanization molding is small. In other words, the green tire using a spiral belt has a larger tire outer diameter before loading the mold than the green tire using a cross belt in which the cord direction is inclined with respect to the tire circumferential direction. If the opening of the sector mold is insufficient, the split position of the sector mold will be smaller than the outer diameter of the raw tire, and the raw tire may be loaded into the mold. It cannot be done and vulcanization molding itself becomes impossible.

On the other hand, in the mold, when the tire after vulcanization molding tries to reduce the split position height W to a position where it does not interfere with the sector mold, the angle θ of the outermost block side wall of the outermost block row is increased to increase the tire width direction. The outer block root P must be moved outward in the tire radial direction. As a result, the base width of the outermost block row is narrowed, resulting in a loss of block rigidity.
JP-A-9-216505

  The present invention has been made to solve the above-mentioned problems, and can suppress the occurrence of cracks from the outermost block row and vulcanize the raw tire before vulcanization molding regardless of the type of tire structure. An object of the present invention is to provide a pneumatic tire for a motorcycle that can be vulcanized and loaded into a tire.

In order to achieve the above object, the invention according to claim 1 is a sector mold including a tread portion forming surface that forms a tread surface of a tire to be molded, and a segment divided into a plurality in the tire circumferential direction; A pneumatic tire for a motorcycle having an outer surface formed by a split mold including a side mold that forms a side surface of a tire to be formed, and having a plurality of grooves and blocks in a tread portion, wherein the sector mold at the time of vulcanization molding And the side mold are positioned on the outer side in the tire radial direction of the block root, which is a contact point between the outer wall surface in the tire width direction of the block on the outermost side in the tire width direction and the virtual groove bottom, and on the outermost side in the tire width direction. A split position equivalent line extending in the tire circumferential direction is formed at a position facing the split position on the outer wall surface in the tire width direction of the block. Cage, from the groove bottom located at the innermost tire radial direction of the groove, with the height position of the top measuring from the groove bottom coincides with the height position of the split position corresponding lines measured from the groove bottom circumferential convex portions having a tire circumferential direction continuous surface smoothly continuous to the direction of tire width direction outer side wall of the tire width direction outermost side of the block, the width direction of the tire outermost adjacent in the tire circumferential direction It is formed integrally with the block so as to connect the blocks, and the circumferential ridge is formed by the side mold at the inner side in the tire radial direction from the top, and the tire radial direction from the top The outer portion is formed by the sector mold.

  Next, the operation of the pneumatic tire for a motorcycle according to claim 1 will be described.

  In the case of a pneumatic tire for a motorcycle in which a split position equivalent line extending in the tire circumferential direction is formed on the outer wall surface in the tire width direction of the outermost block in the tire width direction, for example, a sector mold and a side mold are molded in the circumferential direction. When vulcanization molding is performed in a state where there is a shift, there is a problem that the block side wall surface facing the circumferential direction becomes discontinuous (that is, a small step portion is formed) and becomes a starting point of crack generation. .

  On the other hand, in the pneumatic tire for a motorcycle according to claim 1, the height position of the top coincides with the height position of the split position equivalent line at the groove bottom, and the outermost block in the tire width direction of the outermost block in the tire width direction. The circumferential ridge having a continuous surface that is continuously and smoothly connected to the wall surface in the tire circumferential direction is integrated with the block so as to connect the outermost blocks in the tire width direction adjacent to each other in the tire circumferential direction. In addition, the circumferential ridge is formed of a side mold on the inner side in the tire radial direction from the top and is formed by a sector mold on the outer side in the tire radial direction from the top. Even if a shift occurs, discontinuous portions are formed on the block side wall surfaces by connecting the block side wall surfaces facing the circumferential direction of blocks adjacent to each other in the circumferential direction with the circumferential ridges. There.

  In addition, it is possible to bring the split position of the sector mold and the side mold to the outer wall surface in the tire axial direction of the outermost block in the tire width direction while avoiding the formation of discontinuous portions that become the starting point of crack occurrence in the block. The sector mold can be made to have an inner diameter close to the tire diameter, and it becomes easy to load a raw tire and take out a product tire.

  According to a second aspect of the present invention, in the pneumatic tire for a motorcycle according to the first aspect, the carcass layer straddling the toroidal shape between the pair of bead cores, and the outer diameter of the carcass in the tire radial direction, the breaking strength being 10 cN A spiral belt layer formed by spirally winding a cord of / dtex or more in the tire circumferential direction.

  Next, the operation of the pneumatic tire for a motorcycle according to claim 2 will be described.

  By forming a spiral belt layer formed by spirally winding a cord having a breaking strength of 10 cN / dtex or more spirally in the tire circumferential direction on the outer side in the tire radial direction of the carcass, compared to the case where a so-called cross belt layer is used. Thus, high-speed running performance such as high-speed durability and steering stability can be improved.

  In the case of a pneumatic tire for a motorcycle having such a spiral belt layer, since the diameter of the raw tire before vulcanization is close to the diameter of the product tire, the structure of the pneumatic tire for a motorcycle according to the present invention is reduced. Vulcanization with a mold can be easily performed.

  According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the section height is SH, and the bead baseline is a reference on the inner side in the tire radial direction when the section height SH is measured. T / SH is 0.3 to 0.5, where T is the root height of the block, which is the distance in the tire radial direction to the contact point.

  Next, the operation of the pneumatic tire for a motorcycle according to claim 3 will be described.

  When T / SH is less than 0.3, θ is inevitably small when T is low, and when SH is high, the groove angle of the outermost block increases even when θ is the same. Both indicate that the block rigidity of the outermost block is increased, and the grounding feeling, grip feeling, and slip control required when the motorcycle is tilted are impaired.

  On the other hand, if T / SH exceeds 0.5, the above effect is reversed, and the required block rigidity cannot be obtained. As a result, a shortage of the limit grip and a lack of rigidity are caused.

  Therefore, it is preferable to set T / SH within the range of 0.3 to 0.5 for motocross.

  The invention according to claim 4 is the pneumatic tire for a motorcycle according to any one of claims 1 to 3, characterized in that the height of the block when new is 10 to 20 mm. Yes.

  Next, the operation of the pneumatic tire for a motorcycle according to claim 4 will be described.

  If the block height when new is less than 10 mm, when running on rough terrain, it will not be possible to scrape the soil sufficiently and wheel spin will increase. And it leads to lack of traction and grip.

  If the block height at the time of a new article exceeds 20 mm, when running on rough terrain, the effect of scraping will be improved, but the block rigidity will be reduced. As a result, the rigidity becomes insufficient.

  Therefore, for motocross, it is preferable to set the block height when new to within a range of 10 to 20 mm.

  According to a fifth aspect of the present invention, in the pneumatic tire for a motorcycle according to any one of the first to fourth aspects, the negative rate of the tread portion is 65 to 97%. .

  Next, the operation of the pneumatic tire for a motorcycle according to claim 5 will be described.

  When the negative rate of the tread portion is less than 65%, the effective ground contact area increases on a hard road surface, but conversely, the block ground pressure in the ground contact surface decreases, and an effective edge effect cannot be obtained.

  If the negative rate of the tread portion exceeds 97%, the minimum required ground contact area cannot be obtained, and the block becomes inevitably small, so that the block rigidity cannot be secured.

  Therefore, for motocross, it is preferable that the negative rate of the tread portion is in the range of 65 to 97%.

  As described above, according to the present invention, it is possible to suppress the occurrence of cracks from the outermost block row, and to load the raw tire before vulcanization molding into the vulcanization mold regardless of the tire structure type. It has an excellent effect that enables sulfur molding.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the tire vulcanization mold 10 according to this embodiment is a so-called split mold, and is a fixed annular lower side mold 14, ascending and descending (in the direction of arrow A in FIG. 1). An upper side mold 16 that can be provided and a sector mold 18 composed of a plurality of segments 18A that can move in the radial direction (the direction of arrow B in FIG. 1) are provided.

  The sector mold 18 is formed into a ring shape by combining a plurality of segments 18A in the circumferential direction, and mainly forms a crown portion of the pneumatic tire 12 for a motorcycle. The lower side mold 14 and the upper side mold 16 mainly form the side surface of the pneumatic tire 12 for a motorcycle.

  The pneumatic tire 12 for a motorcycle that is molded by the tire vulcanization mold 10 according to the present embodiment is a so-called motocross tire having a block pattern.

  The pneumatic tire 12 for a motorcycle includes a pair of bead cores 26, a carcass 28 whose both ends are locked to the bead core 26, and a main belt layer 30 that reinforces the crown portion of the carcass 28.

  The main belt layer 30 of the present embodiment is a so-called spiral belt in which one cord covered with rubber or a ribbon-like strip covered with a plurality of cords is wound spirally in the circumferential direction.

  The cord used for the main belt layer 30 preferably has a breaking strength of 10 cN / dtex or more. As a cord having a breaking strength of 10 cN / dtex or more, for example, an aramid cord or the like can be used.

  A tread rubber layer 21 that forms the tread portion 20 is disposed outside the main belt layer 30 in the tire radial direction.

  A plurality of blocks 22 are formed in the tread portion 20.

  In FIG. 1, reference sign BL is a bead base line, reference sign TW is a tread width, reference sign SH is a section height (section height), reference sign SW is a tire width, reference sign WH is a tire width height, and reference sign S is a tread portion 20. , DH is falling height, W is split position height, P is block root, T is block root height, D is rim diameter, and θ is the outermost block in the tire width direction ( In the shoulder block 22, the angle between the block outer wall surface 22 a on the outer side in the tire width direction and the tire radial direction, the symbol h indicates the block height.

  As is well known, the bead base line BL is a reference line on the inner side in the tire radial direction when the section height of the tire is measured.

  In the case of the pneumatic tire 12 for a motorcycle, the tire width SW is the maximum width of the side portion 32 excluding the tread portion 20.

  The tire width height WH is a dimension from the bead base line BL to the maximum width portion of the side portion 32 measured along the tire radial direction.

  The drop height DH is a dimension measured along the tire radial direction from the maximum diameter portion (in the embodiment, the intersection of the tread surface and the tire equator surface CL) to the ground contact edge S of the tread portion 20.

  The block root P is the inner end portion in the tire radial direction of the block outer wall surface 22a on the outer side in the tire width direction in the outermost block 22 in the tire width direction.

  The block root height T is a dimension from the bead base line BL to the block root P measured along the tire radial direction.

  The split position height W is determined from the maximum diameter portion of the tread portion 20 (in the embodiment, the intersection of the tread surface and the tire equator surface CL), the segment 18A on the inner surface of the mold, the lower side mold 14 (and the upper side mold 16). It is the dimension measured along the tire radial direction to the contact point.

  As shown in FIG. 1 and FIG. 2, in the pneumatic tire 12 for a motorcycle according to this embodiment, the groove bottom between the outermost block 22 and the block 22 adjacent to each other in the circumferential direction in the tire width direction, A built-up portion 34 is formed.

  The build-up portion 34 connects the block circumferential wall surfaces 22b facing the tire circumferential direction of the outermost block 22 in the tire width direction, and the position thereof is in the vicinity of the block root P.

  The build-up portion 34 of the present embodiment has a substantially triangular cross-sectional shape, and the build-up portion outer wall surface 34a on the outer side in the tire width direction is integrally continuous with the block outer wall surface 22a of the block 22 in the circumferential direction.

  Further, the position of the top 34P of the build-up portion 34 coincides with the position of the contact point between the segment 18A and the lower side mold 14 (and the upper side mold 16) on the inner surface of the mold.

  Therefore, the built-up portion 34 is formed by the lower side mold 14 (or the upper side mold 16) in the tire radial inner side portion (the built-up portion outer wall surface 34a) from the top portion 34P, and the tire radial direction outer portion from the top portion 34P. (The built-up portion inner wall surface 34 b) is formed by the sector mold 18.

  In addition, as shown in FIG. 2, the block outer wall surface 22a has a peripheral portion at a portion facing the split position between the lower side mold 14 (or the upper side mold 16) and the sector mold 18 at the time of vulcanization molding. A split line equivalent line (illustrated by a two-dot chain line) 36 of the streak extending in the direction is formed.

For motocross, the T / SH is set within a range of 0.3 to 0.5, the block height h when new is within a range of 10 to 20 mm, and the negative rate of the tread portion 20 is 65 to 65 mm. It is preferable to be within the range of 97%.
(Function)
In the pneumatic tire 12 for a motorcycle according to the present embodiment, the height position of the top portion 34P coincides with the height position of the split position PL equivalent line at the groove bottom, and the block outer wall surface 22a of the outermost block 22 in the tire width direction. The build-up portion 34 having the build-up portion outer wall surface 34a that is continuously and smoothly connected to the tire circumferential direction is connected to the outermost blocks 22 in the tire width direction adjacent to each other in the tire circumferential direction. 22, and the built-up portion 34 is formed such that the inner portion in the tire radial direction from the top portion 34P is formed by the lower side mold 14 or the upper side mold 16, and the outer portion in the tire radial direction from the top portion 34P. Is formed by the sector mold 18, for example, even if circumferential mold displacement occurs, the block 22 adjacent to the circumferential direction faces the circumferential direction. Linked blocks circumferential wall 22b each other by being connected by the padding unit 34, the discontinuous portion comprising a base point of a crack generated in the block circumferential direction wall 22b is not formed.

  Further, since the split position PL can be brought to the block outer wall surface 22a on the outer side in the tire width direction, the inner diameter of the sector mold 18 is set so as not to form a discontinuous portion that becomes a base point of occurrence of cracks in the block 22. This makes it easy to load a raw tire and take out a product tire. In the pneumatic tire 12 for a motorcycle according to the present embodiment, the main belt layer 30 has a spiral structure, and the diameter of the raw tire before vulcanization is close to the diameter of the product tire. The diameter of the PL can be set large, the raw tire can be easily loaded, and the vulcanization molding by the split mold can be performed without any problem.

  Further, in the pneumatic tire 12 for a motorcycle according to the present embodiment, the falling height DH can be increased while avoiding the formation of a discontinuous portion that becomes a base point of occurrence of cracks in the block 22, and the steering stability can be improved.

  In addition, since the main belt layer 30 having a spiral structure is formed by spirally winding a cord having a breaking strength of 10 cN / dtex or more in the tire circumferential direction, the high-speed durability is higher than when a cross belt layer is used. High-speed driving performance such as steering stability can be improved.

  In the pneumatic tire 12 for motorcycles for motocross, when T / SH is less than 0.3, θ is inevitably small when T is low, and when SH is high, the outermost block is equal even if θ is the same. The groove angle of 22 is increased. Both show that the block rigidity of the outermost block 22 is increased, and the grounding feeling, grip feeling, and slip controllability required when the motorcycle is tilted are impaired.

  On the other hand, if T / SH exceeds 0.5, the above effect is reversed, and the required block rigidity cannot be obtained. As a result, a shortage of the limit grip and a lack of rigidity are caused.

  Further, in the pneumatic tire 12 for motorcycles for motocross, when the block height h at the time of a new article is less than 10 mm, when traveling on rough terrain, the soil cannot be scraped out sufficiently and the wheel spin increases. . And it leads to lack of traction and grip.

  On the other hand, when the new block height h exceeds 20 mm, when running on rough terrain, the effect of scraping is improved, but the block rigidity is lowered. As a result, the rigidity becomes insufficient.

  In the pneumatic tire 12 for motorcycles used for motocross, if the negative rate of the tread portion 20 is less than 65%, the effective ground contact area increases on a hard road surface, but conversely, the block ground pressure in the ground contact surface is small. Therefore, an effective edge effect cannot be obtained.

On the other hand, if the negative rate of the tread portion 20 exceeds 97%, the minimum required ground contact area cannot be obtained, and the block 22 is inevitably small, so that the block rigidity cannot be secured.
(Test example)
In order to confirm the effect of the present invention, a conventional full mold, a conventional split mold, and a split mold for molding the tire of the present invention are prepared, and two types of raw tires having different internal structures are used for each mold. Then, vulcanization was performed, and the pot stock, mold deviation, and crack durability were compared.

  Example Split Mold: The structure is the same as the split mold described in the above-described embodiment. The product tire has a built-up portion at the groove bottom.

  Conventional split mold: The split position comes to the outer wall surface in the tire axial direction of the outermost block, and a tire that does not form a built-up portion is formed.

  Conventional full mold: Conventional general structure.

  As the raw tire, one type of belt having a cross belt structure and one type of belt having a spiral belt structure were used. Raw tires with a spiral belt structure have less diameter expansion during vulcanization molding compared to the cross belt structure.

  Table 1 below shows the relationship between the test tire, the tire structure, and the mold type at the time of molding.

Cross belt structure: 2-belt structure using Kevlar cord (cord angle (direction of circumference) is 25 °)
Spiral belt structure: Kevlar cord spirally wound (1 layer)
In all tires, the carcass has a one-ply structure in which nylon cords with an angle of 90 ° on the tire equatorial plane are embedded.

  Kettle stock: Ease of taking out the problem that the tire after vulcanization molding is difficult to take out due to interference with the mold. Evaluation is based on a 10-point scale.

  Mold deviation: Visual evaluation. If there is no level difference when touched, the product is accepted, but if there is a level difference, it becomes a defective product according to the inspection standard.

  Crack durability: A professional rider traveled on rough terrain. 30 minutes of continuous running was performed with each test tire, and the evaluation was performed based on the number of running times (time) until a crack occurred. The higher the number of trips until the crack appears, the higher the score.

  As a result of the test, when the tire to which the present invention was applied (test types 4 and 5) was produced, it was easy to load the pot.

  The tire to which the present invention is applied (test types 4 and 5) does not cause a shift as a base point of crack generation on the wall surface of the block, so that it is understood that the crack durability is good.

It is sectional drawing of a pneumatic tire for a mold and a motorcycle. 1 is a partial perspective view of a pneumatic tire for a motorcycle. It is sectional drawing of the conventional mold and the pneumatic tire for two-wheeled vehicles. It is a fragmentary perspective view of the conventional pneumatic tire for two-wheeled vehicles. It is sectional drawing of the conventional pneumatic tire for two-wheeled vehicles.

Explanation of symbols

10 Tire vulcanization mold (split mold)
12 Pneumatic tires for motorcycles 14 Lower side mold 16 Upper side mold 18 Sector mold 20 Tread part 22 Block 22a Block outer wall 28 Carcass 30 Main belt (spiral belt layer)
34 Overlaying part (circumferential ridge)
34a Inclined surface (continuous surface)
36 Split position equivalent line PL Split position P Block root (contact)

Claims (5)

A split mold including a sector mold having a tread portion forming surface that forms a tread surface of a tire to be formed and divided into a plurality of segments in the tire circumferential direction, and a side mold that forms a side surface of the tire to be formed An outer surface is formed by a pneumatic tire for a motorcycle including a plurality of grooves and blocks in a tread portion,
The split position between the sector mold and the side mold at the time of vulcanization molding is more radially outward than the base of the block, which is a contact point between the outer wall surface in the tire width direction of the outermost block in the tire width direction and the virtual groove bottom. Position to,
On the outer wall surface in the tire width direction of the outermost block in the tire width direction, a split position equivalent line extending in the tire circumferential direction is formed at a position facing the split position,
From the groove bottom located at the innermost tire radial direction of the groove, with the height position of the top measuring from the groove bottom coincides with the height position of the split position corresponding lines measured from the groove bottom, wherein circumferential convex portions having a continuous surface smoothly continuous in the tire circumferential direction of tire width direction outer side wall surface of the block in the tire width direction outermost side, in the tire width direction outermost side of the block adjacent to each other in the tire circumferential direction Are formed integrally with the block so as to connect
In the circumferential ridge portion, an inner portion in the tire radial direction from the top portion is formed by the side mold, and an outer portion in the tire radial direction from the top portion is formed by the sector mold.
This is a pneumatic tire for motorcycles. A carcass layer straddling a toroid between a pair of bead cores;
A spiral belt layer disposed outside the carcass in the tire radial direction and formed by spirally winding a cord having a breaking strength of 10 cN / dtex or more in the tire circumferential direction;
The pneumatic tire for a motorcycle according to claim 1, characterized by comprising:   T / SH where SH is the section height and T is the block root height, which is the distance in the tire radial direction from the bead base line to the contact point, which is the inner reference in the tire radial direction when measuring the section height SH. The pneumatic tire for a motorcycle according to claim 1 or 2, wherein the tire is 0.3 to 0.5.   The pneumatic tire for a motorcycle according to any one of claims 1 to 3, wherein the height of the block when new is 10 to 20 mm.   The pneumatic tire for a motorcycle according to any one of claims 1 to 4, wherein a negative rate of the tread portion is 65 to 97%.

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