JP3733056B2 - Pneumatic radial tire - Google Patents

Description

【００５１】
【発明の効果】
叙上の如く本発明は、タイヤ周方向に短繊維を配向させた短繊維補強ゴム層を、ビードエーペックスゴムの少なくとも内側面を含む側面に沿って配しているため、耐久性及び乗り心地性を悪化させることなく、操縦安定性を向上させることができる。
【図面の簡単な説明】
【図１】 本発明の一実施例を外の短繊維補強ゴム層をのぞいて示すタイヤの断面図である。
【図２】 ビード部の内の短繊維補強ゴム層を拡大して示す断面図である。
【図３】短繊維の配合量に基づく、周方向及び半径方向の複素弾性率Ｅａ＊、Ｅｂ＊の変化の一例を示す線図である。
【図４】内の短繊維補強ゴム層の効果の一つを誇張して示す斜視図である。
【図５】 本発明の実施例を示す、ビード部の拡大断面図である。
【図６】表１の比較例１を説明する線図である。
【符号の説明】
２ トレッド部
３ サイドウォール部
４ ビード部
５ ビードコア
６ カーカス
８ ビードエーペックスゴム
１０ 内の短繊維補強ゴム層
２０ 外の短繊維補強ゴム層
Ｇ 短繊維補強ゴム[0001]
BACKGROUND OF THE INVENTION
The present invention provides a pneumatic radial with improved steering stability without deteriorating durability and ride comfort by providing a short fiber reinforced rubber layer adjacent to at least the inner side surface of the bead apex rubber. Regarding tires.
[0002]
[Background Art and Problems to be Solved by the Invention]
In recent years, with higher output and higher performance of automobiles, improvement of steering stability as well as high ride comfort is strongly desired for tires.
[0003]
On the other hand, in pneumatic radial tires, it is known that the steering stability performance can be improved by increasing the lateral stiffness of the tire. Therefore, conventionally, a cord reinforcement layer using a steel cord or an organic fiber cord is used as a bead portion. It is provided from the side wall to the side wall portion to increase the bending rigidity of the side wall.
[0004]
However, the use of such a cord reinforcing layer is accompanied by an increase in tire longitudinal rigidity, which leads to a deterioration in riding comfort. Also, the cord reinforcement layer tends to concentrate stress at its end, especially when it is used in high performance tires that reduce the tire flatness to 55% or less and increase the contact width and contact area. Since the flexible region is narrow and stress concentration becomes remarkable, the durability tends to be impaired.
[0005]
Therefore, the present inventor noticed that not only the lateral stiffness of the tire but also the torsional stiffness in the rotational direction, that is, the circumferential stiffness is greatly involved in the steering stability, and by orienting the short fibers in the tire circumferential direction, Proposed to arrange a short fiber reinforced rubber layer with significantly increased circumferential complex elastic modulus while keeping the complex elastic modulus in the tire radial direction without protruding from the bead apex rubber and along the side surface. . As a result, it has been found that the torsional rigidity of the tire is effectively increased and the steering stability is improved, while the longitudinal rigidity of the tire can be kept low.
[0006]
That is, the present invention is based on the fact that the short fiber reinforced rubber layer in which short fibers are oriented in the tire circumferential direction is disposed along the side surface including at least the inner side surface of the bead apex rubber, and the durability and ride comfort are deteriorated. The object of the present invention is to provide a pneumatic radial tire with improved steering stability.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application is characterized by a taper extending from the tread portion to the bead core of the bead portion through the sidewall portion and the radially outer surface of the bead core toward the outer side in the tire radial direction. A pneumatic radial tire having a bead apex rubber extending in a shape,
An inner short fiber reinforced rubber layer is disposed along the inner surface in the tire axial direction of the bead apex rubber and extending radially from the bead core to an inner height position from the radially outer end of the bead apex rubber. And
The short fiber reinforced rubber layer is composed of a short fiber blended rubber in which 10 to 30 parts by weight of short fibers are blended with 100 parts by weight of rubber, and the short fibers are oriented in the tire circumferential direction.
In addition, an outer short fiber reinforced rubber layer extending from the bead core to an inner height position from the radially outer end of the bead apex rubber along the tire axial direction outer surface of the bead apex, and The radially outer end of the inner short fiber reinforced rubber layer is positioned radially inward from the radially outer end of the outer short fiber reinforced rubber layer, and the short fibers of the outer short fiber reinforced rubber layer are disposed in the tire. It is characterized by being oriented in the circumferential direction.
[0008]
The invention of claim 2 is characterized in that the short fiber reinforced rubber layer has a thickness of 0.3 to 2.0 mm.
[0009]
According to a third aspect of the present invention, the short fiber reinforced rubber layer includes a complex elastic modulus Ea * in the tire circumferential direction that is greater than a complex elastic modulus E * of the bead apex rubber and a radial complex elastic modulus Eb *. Is smaller than the complex elastic modulus E * of the bead apex rubber, and the ratio Ea * / Eb * between the complex elastic modulus Ea * and Eb * is 10-30.
[0010]
According to a fourth aspect of the present invention, the short fiber reinforced rubber layer includes a radial complex elastic modulus Eb * of 10 Mpa or less.
[0011]
Further, in the invention of claim 5, the inner short fiber reinforced rubber layer is characterized in that a radial distance L1 between the outer end in the radial direction and the outer end of the bead apex rubber is 3 mm or more. .
[0012]
The invention according to claim 6 is characterized in that the radial distance between the outer ends of the inner and outer short fiber reinforced rubber layers is 5 mm or more .
[0013]
In the invention of claim 7, the radial distance L3 between the height position of the outer end of the outer short fiber reinforced rubber layer and the outer end of the bead apex rubber is set to 3.0 mm or more. It is said.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a meridional sectional view illustrating a case where the pneumatic radial tire of the present invention is a high-performance passenger car tire having a tire flatness ratio of 55% or less. FIG. 2 is an enlarged cross-sectional view of the bead portion.
[0015]
As shown in FIG. 1, the pneumatic radial tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, inside the tread portion 2 and outside the carcass 6. The bead portion 4 is provided with a bead apex rubber 8 that rises outward in the tire radial direction from the radial outer surface of the bead core 5.
[0016]
The belt layer 7 is composed of two or more belt plies 7A and 7B in this example, in which high elasticity belt cords are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction. The belt plies 7A and 7B are stacked with different inclination directions so that the belt cords cross each other between the plies, thereby increasing the belt rigidity, and having a substantially full width of the tread portion 2 with a tagging effect. Strongly reinforced. As the belt cord, a steel cord or a high modulus organic fiber cord such as an aromatic polyamide fiber comparable to this is preferably used.
[0017]
Further, in this example, the case where the band layer 9 is disposed outside the belt layer 7 is illustrated for the purpose of increasing the restraining force on the belt layer 7 and improving the high speed durability performance. The band layer 9 has a band cord spirally wound at an angle of, for example, 5 ° or less with respect to the tire circumferential direction, and extends at least covering the outer end portion of the belt layer 7 in the tire axial direction.
[0018]
The carcass 6 is formed of one or more carcass plies 6A in this example in which carcass cords are arranged at an angle of 75 to 90 ° with respect to the tire circumferential direction. The carcass ply 6 </ b> A is integrally provided with folded portions 6 b that are folded back from the inside around the bead core 5 at both ends of the main body portion 6 a that extends between the bead cores 5 and 5. As the carcass cord, in addition to organic fiber cords such as nylon, rayon, polyester, and aromatic polyamide, steel cords can be used as appropriate, but organic fiber cords are preferable from the viewpoint of weight reduction.
[0019]
Next, the bead apex rubber 8 has a triangular cross section that extends between the main body portion 6a and the folded portion 6b of the carcass ply 6A and extends outward in the tire radial direction. In this example, in order to ensure the tire rigidity necessary as a high-performance tire, the height h1 of the radially outer end 8e from the bead base line BL is 0.25 to 0.5 times the tire cross-section height HT. The range is as follows. The bead apex rubber 8 is made of rubber having a complex elastic modulus E * of 35 to 60 Mpa and higher elasticity than the side wall rubber (usually having a complex elastic modulus of 2.5 to 6 Mpa).
[0020]
And in this embodiment, in such a tire 1, in order to improve steering stability without deteriorating durability and riding comfort, the short fiber reinforced rubber layer 10 in the bead part 4 and the outer A short fiber reinforced rubber layer 20 is provided. In FIG. 1, only the short fiber reinforcing rubber layer 10 of the inner, are shown for the explanation.
[0021]
The short fiber reinforced rubber layer 10 is a thin rubber layer having a substantially constant rubber thickness t, as shown in FIG. 2, along the tire axially inner side surface of the bead apex rubber 8. And it extends in the radial direction from the bead core 5 to a height position inward from the outer end 8 e of the bead apex rubber 8.
[0022]
The short fiber reinforced rubber layer 10 is composed of a short fiber blended rubber G in which 10 to 30 parts by weight of short fibers are blended with 100 parts by weight of rubber, and the short fibers are oriented in the tire circumferential direction. . “Short fibers are oriented in the tire circumferential direction” means that 90% or more of the short fibers are oriented in an angle range of ± 20 degrees or less centering on the tire circumferential direction.
[0023]
Due to the orientation of the short fibers, as shown in FIG. 3, the short fiber reinforced rubber layer 10 has a complex elastic modulus Ea * in the tire circumferential direction while suppressing an increase in the complex elastic modulus Eb * in the radial direction. The ratio Ea * / Eb * can be increased to, for example, 10 or more. In addition, FIG. 3 shows an example of the change of the complex elastic modulus Ea * and Eb * of the circumferential direction and radial direction based on the compounding quantity of a short fiber.
[0024]
Thus, since the short fiber reinforced rubber layer 10 in the inside greatly increases the complex elastic modulus Ea * in the tire circumferential direction, it effectively increases the circumferential rigidity of the tire, that is, the torsional rigidity during tire rotation. be able to. As exaggeratedly shown in FIG. 4, when the large lateral force F acts and the bead portion 4 curves inward in the tire axial direction, the inner side of the bead apex rubber 8 is pulled and the outer side is compressed. Therefore, when the short fiber reinforced rubber layer 10 is provided on the inner side which is the tension side, the cornering force is increased such that the drag can be obtained more effectively than when provided on the outer side, and this is combined with the torsional rigidity. And excellent steering stability. For that purpose, it is preferable that the inner short-fiber reinforced rubber layer 10 has its radially inner end e2 as close to the bead core 5 as possible with a radial distance K from the bead core 5 of 3 mm or less.
[0025]
On the other hand, in the short fiber reinforced rubber layer 10 as shown in FIG. 3, the longitudinal rigidity of the tire can be kept low, such as almost no influence on the complex elastic modulus Eb * in the radial direction can be avoided, and the decrease in ride comfort is suppressed. it can. For this purpose, the complex elastic modulus Ea * in the tire circumferential direction is larger than the complex elastic modulus E * of the bead apex rubber (Ea *> E *), and the complex elastic modulus Eb * in the radial direction is a bead. It is necessary to be smaller (Eb * <E *) than the complex elastic modulus E * of the apex rubber.
[0026]
In order to exhibit the effects of improving the steering stability and suppressing the decrease in ride comfort more preferably, the ratio Ea * / Eb * is preferably set to 10 to 30, and the ratio Ea * / Eb * When the value is less than 10, the steering stability improvement effect becomes insufficient, and the steering response tends to decrease. Further, it is technically difficult for the ratio Ea * / Eb * to exceed 30, which causes a disadvantage in productivity and production cost, and the rubber strength tends to decrease. Therefore, the ratio Ea * / Eb * is more preferably 15-25.
[0027]
At this time, the complex elastic modulus Eb * in the tire radial direction is preferably 10 MPa or less, and further preferably 5 MPa or less for ride comfort.
[0028]
The complex elastic modulus is a value measured by using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. at a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of ± 1%.
[0029]
Here, the short fibers tend to be oriented in the extruding direction when the short fiber compounded rubber is extruded into a sheet shape by an extruder or a calender roll. By using this, the short fibers of the short fiber reinforced rubber layer 10 are used. Can be oriented in the circumferential direction. However, when the thickness t of the inner short fiber reinforced rubber layer 10 exceeds 2.0 mm, it becomes difficult to ensure the ratio Ea * / Eb * to 10 or more, for example, the orientation of the short fibers deteriorates. . As a result, the effect of improving the steering stability is reduced, and the tire weight is also increased to increase the rolling resistance. On the other hand, if the thickness t is smaller than 0.3 mm, the material is too thin to exhibit the reinforcing effect, and it is difficult to handle and disadvantageous in productivity. Thus, the thickness t is preferably 0.3 to 2.0 mm, and more preferably 0.3 to 1.5 mm.
[0030]
Next, as the rubber base material of the short fiber compounded rubber, for example, a kind of diene rubber such as natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), or isoprene rubber (IR), or What combined multiple types can use it conveniently.
[0031]
Examples of the short fibers include organic fibers such as nylon, polyester, aramid, rayon, vinylon, cotton, cellulose resin, crystalline polybutadiene, and inorganic fibers such as metal fibers, whiskers, boron, and glass fibers. These can be used alone or in combination of two or more. More preferably, the short fiber may be subjected to an appropriate surface treatment in order to improve the adhesion to the rubber substrate.
[0032]
The average fiber length L of the short fibers is preferably 20 μm or more, particularly preferably 50 to 5000 μm. The aspect ratio L / D between the average fiber length L and the fiber diameter D is preferably 10 or more, particularly preferably 20 to 500. When the average fiber length L is less than 20 μm and the aspect ratio L / D is less than 10, a sufficient difference can be secured between the complex elastic modulus Ea * and Eb * even when the short fibers are oriented with high accuracy. It becomes difficult to achieve both improvement in handling stability and suppression of reduction in ride comfort, such as disappearance. On the other hand, when the average fiber length L is greater than 5000 μm and the aspect ratio L / D is greater than 500, the orientation of the short fibers itself is lowered, and the above-mentioned compatibility is similarly difficult.
[0033]
Further, the blending amount of the short fiber needs to be 10 to 30 parts by weight, and if it is less than 10 parts by weight, the reinforcing effect is inferior, and the necessary complex elastic modulus Ea * in the tire circumferential direction cannot be secured. The effect of improving sex is not demonstrated. On the other hand, if the amount exceeds 30 parts by weight, the complex elastic modulus Ea * in the tire radial direction tends to increase even when the short fibers are oriented with high precision, and the riding comfort is reduced. In addition, the viscosity of the unvulcanized rubber increases and the processability also decreases.
[0034]
In the short fiber blended rubber, carbon black can be further blended with the rubber base material, and the carbon black having an iodine adsorption of 30 to 90 mg / g can be suitably used. Carbon black having an iodine adsorption of less than 30 mg / g has low rubber reinforcing properties and is inferior in both strength and cut resistance. On the other hand, if it exceeds 90 mg / g, exothermicity increases and rolling resistance is deteriorated.
[0035]
The compounding amount of the carbon black is 40 parts by weight or less, preferably 20 to 30 parts by weight with respect to 100 parts by weight of the rubber base material. When the amount exceeds 40 parts by weight, the heat generation property of the rubber increases and the rolling resistance also increases. Getting worse. In addition to the above short fibers and carbon black, conventional additives for tire rubber such as oil, anti-aging agent, wax, vulcanization accelerator and the like can be appropriately blended with the short fiber blended rubber.
[0036]
Further, in the short fiber reinforced rubber layer 10 in the present embodiment, the radially outer end e1 is held inward in the radial direction with respect to the outer end 8e of the bead apex rubber 8, so that the stress concentration is reduced. It is possible to prevent deterioration of durability. In particular, the radial distance L1 between the outer end e1 and the outer end 8e is preferably 3 mm or more from the viewpoint of durability.
[0037]
Here, when the short fiber reinforced rubber layer provided in the bead part 4 is only the short fiber reinforced rubber layer 10 as in this example, that is, the short fiber reinforced rubber layer is not disposed on the outer surface of the bead apex rubber 8. In this case, the height Hi of the outer end e1 from the bead core 5 is preferably 0.1 to 0.25 times the tire cross-section height HT. If it is less than 0.1 times, the effect of improving the steering stability is not sufficiently exhibited. Conversely, if it exceeds 0.25 times, there is a disadvantage that the riding comfort deteriorates.
[0038]
Further, since the short fiber reinforced rubber layer 10 is disposed between the bead apex rubber 8 and the carcass ply 6A, the rubber thickness t is uniform, for example, the rubber flow during vulcanization molding is suppressed. Can be secured. That is, when it is provided in another part, the rubber thickness t is partially changed, and there is no inconvenience such as damage due to weakness of strength, and durability can be maintained.
[0039]
Further, in the short fiber reinforced rubber layer 10 as described above, it is preferable to extend substantially linearly from the inner end e2 to the outer end e1 as in this example, whereby the torsional rigidity can be increased more effectively. The “substantially linear” means that the diameter of a three-point arc passing through the inner end e2, the outer end e1, and the middle point of the short fiber reinforced rubber layer 10 is 100 mm or more.
[0040]
In FIG. 5, in addition to the inner short fiber reinforced rubber layer 10, the outer short fiber reinforced rubber layer 20 is also shown.
[0041]
The outer short fiber reinforced rubber layer 20 extends from the bead core 5 to the inner height of the outer end 8e of the bead apex rubber 8 along the tire axial direction outer surface of the bead apex. The outer short fiber reinforced rubber layer 20 is composed of the short fiber compounded rubber G in which short fibers are oriented in the circumferential direction. Therefore, the rubber properties such as the complex elastic modulus Ea * and Eb * are improved. The rubber layer 10 has substantially the same physical properties as the rubber. The rubber thickness is also in the range of 0.3 to 2.0 mm.
[0042]
Accordingly, like the inner short fiber reinforced rubber layer 10, it is possible to increase the torsional rigidity in the circumferential direction while maintaining the tire longitudinal rigidity low, and in combination with the inner short fiber reinforced rubber layer 10, steering stability is improved. Further improvement can be achieved. Since the outer surface of the bead apex rubber 8 is close to the neutral line during bending deformation, the outer short fiber reinforced rubber layer 20 can increase the torsional rigidity in the circumferential direction while suppressing the increase in bending rigidity as much as possible. Therefore, it becomes a more preferable aspect.
[0043]
At this time, if the height positions of the outer ends e1 and f1 of the inner and outer short fiber reinforced rubber layers 10 and 20 are too close, the durability is lowered due to stress concentration. Therefore, in this example, the outer end e1 is terminated inward in the radial direction with respect to the outer end f1, thereby distributing stress. This is because the inner side surface of the bead apex rubber 8 is far from the neutral line at the time of bending deformation, and therefore the inner short fiber reinforced rubber layer 10 has a larger influence on the bending rigidity, and therefore, Lowering the end e1 is advantageous for ride comfort.
[0044]
In order to maintain the durability, it is preferable that the radial distance L2 between the outer ends e1 and f1 is 5 mm or more, and for the same purpose, the outer end f1 and the outer side of the bead apex rubber 8 are separated from each other. The radial distance L3 between the end 8e is preferably 3.0 mm or more.
[0045]
The height Ho of the outer end f1 of the outer short fiber reinforced rubber layer 20 from the bead core 5 is preferably 0.1 to 0.25 times the tire cross-section height HT. The height Hi of the short fiber reinforced rubber layer 10 may be reduced to 0.08 × HT.
[0046]
In addition, although the said effect by the said short fiber reinforcement rubber layers 10 and 20 can function effectively with a high performance tire with a tire flatness ratio of 30-55% like this example, this invention is in embodiment shown in figure. Without being limited, the present invention can be carried out with various modifications.
[0047]
【Example】
A tire having a tire size of 215 / 45ZR17 was prototyped based on the specifications in Table 1, and the handling stability and riding comfort of each sample tire were tested. In Comparative Example 1, as schematically shown in FIG. 6, a cord reinforcing layer of a steel cord is provided so as to protrude from the outer end of the bead apex rubber.
The test method is as follows.
[0048]
(1) Steering stability;
-Tires are mounted on all wheels of a passenger vehicle (domestic FR passenger car, displacement of 2500 cc) under conditions of rim (17 x 7 JJ) and internal pressure (200 kPa), and run at high speed on a dry asphalt road surface at a speed of 120 km / H. In addition, the straight running stability and the lane change stability are indicated by an index with a conventional example of 100 by sensory evaluation of the driver. A larger index is better.
・ Using the same test vehicle, run at a speed of 80 km / H on a wet asphalt road. The driving stability performance including the straight running stability and the lane change stability at that time is 100 as the conventional example based on the driver's sensory evaluation. The index is displayed. A larger index is better.
[0049]
(2) Ride comfort;
-The ride comfort when driving on the asphalt road surface (good road) using the test vehicle is displayed as an index with a conventional example of 100 by sensory evaluation of the driver. A larger index is better.
-The ride comfort when driving on the Belgian road surface (bad road) using the test vehicle is displayed as an index with the conventional example being 100 based on the sensory evaluation of the driver. A larger index is better.
[0050]
[Table 1]

[0051]
【The invention's effect】
As described above, in the present invention, the short fiber reinforced rubber layer in which the short fibers are oriented in the tire circumferential direction is disposed along the side surface including at least the inner side surface of the bead apex rubber. The steering stability can be improved without deteriorating the engine.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a tire showing an embodiment of the present invention except for an outer short fiber reinforced rubber layer .
FIG. 2 is an enlarged cross-sectional view showing a short fiber reinforced rubber layer in a bead portion.
FIG. 3 is a diagram showing an example of changes in complex elastic moduli Ea * and Eb * in the circumferential direction and radial direction based on the blending amount of short fibers.
FIG. 4 is a perspective view exaggerating one of the effects of an inner short fiber reinforced rubber layer.
FIG. 5 is an enlarged cross-sectional view of a bead portion showing an embodiment of the present invention.
6 is a diagram for explaining Comparative Example 1 in Table 1. FIG.
[Explanation of symbols]
2 tread portion 3 side wall portion 4 bead portion 5 bead core 6 carcass 8 bead apex rubber 10 short fiber reinforced rubber layer 20 outer short fiber reinforced rubber layer G short fiber reinforced rubber

Claims (7)

A pneumatic radial tire comprising a carcass extending from a tread portion through a sidewall portion to a bead core of a bead portion, and a bead apex rubber extending in a tapered shape from a radially outer surface of the bead core toward a radially outer side of the tire. And
An inner short fiber reinforced rubber layer is disposed along the inner surface in the tire axial direction of the bead apex rubber and extending radially from the bead core to an inner height position from the radially outer end of the bead apex rubber. And
The short fiber reinforced rubber layer is composed of a short fiber blended rubber in which 10 to 30 parts by weight of short fibers are blended with 100 parts by weight of rubber, and the short fibers are oriented in the tire circumferential direction.
In addition, an outer short fiber reinforced rubber layer extending from the bead core to an inner height position from the radially outer end of the bead apex rubber along the tire axial direction outer side surface of the bead apex, and The radially outer end of the inner short fiber reinforced rubber layer is positioned radially inward from the radially outer end of the outer short fiber reinforced rubber layer, and the short fibers of the outer short fiber reinforced rubber layer are disposed in the tire. A pneumatic radial tire characterized by being oriented in the circumferential direction.   The pneumatic radial tire according to claim 1, wherein the short fiber reinforced rubber layer has a thickness of 0.3 to 2.0 mm.   The short fiber reinforced rubber layer includes a complex elastic modulus Ea * in the tire circumferential direction that is larger than a complex elastic modulus E * of the bead apex rubber, and a complex elastic modulus Eb * in the radial direction of the complex elastic modulus of the bead apex rubber. 3. The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is smaller than E * and has a ratio Ea * / Eb * between the complex elastic modulus Ea * and Eb * of 10 to 30. 4. The pneumatic radial tire according to claim 3, wherein the inner short fiber reinforced rubber layer has a complex elastic modulus Eb * in the radial direction of 10 Mpa or less.   The inner short fiber reinforced rubber layer has a radial distance L1 between the outer end in the radial direction and the outer end of the bead apex rubber of 3 mm or more. Pneumatic radial tire described in 2.   6. The pneumatic radial tire according to claim 5, wherein a radial distance between outer ends of the inner and outer short fiber reinforced rubber layers is 5 mm or more.   The radial distance L3 between the height position of the outer end of the outer short fiber reinforced rubber layer and the outer end of the bead apex rubber is set to 3.0 mm or more. A pneumatic radial tire according to any one of the above.

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