JP2002301911A - Run flat tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a run flat travel distance without impairing ride comfort. SOLUTION: This run flat tire 1 comprises a carcass 6 ranging from a tread section 2 via a side wall section 3 to a bead core 5 of a bead section 4, a bead apex rubber 8 extending outward from the outside surface in the tire radial direction of the bead core 5 in the tapered shape, and a side reinforcing rubber layer 10 arranged on the side wall section 3 and forming a roughly crescent- shaped cross section. The side reinforcing rubber layer 10 is composed of a first rubber section 11 having a maximum thick section 11a on the tread section side and a second rubber section 12 having a maximum thick section 12a on the bead section side. JIS durometer hardness S1 of the first rubber section 11, JIS durometer hardness S2 of the second rubber section 12, and JIS durometer hardness S3 of the bead apex rubber 8 have the following relationship: S1<S2, S3<=S2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a run-flat tire that can run at a relatively high speed over a relatively long distance even when air in the tire is released due to a puncture or the like.

[0002]

2. Description of the Related Art Conventionally, even when air in a tire escapes due to a puncture or the like, the rim does not come off and can travel a relatively long distance while being restricted to a certain speed. Various run flat tires have been proposed.

[0003] Generally, such a run flat tire is provided with a reinforcing rubber layer made of a relatively hard rubber having a substantially crescent cross section on the side wall portion, and in the event of a puncture, a vertical load of the tire is applied by the reinforcing rubber layer. By supporting,
There are known tires that suppress longitudinal deformation of a tire and enable continuous running (run-flat running) under certain conditions (Japanese Patent Application Laid-Open Nos. 53-18104 and 64-30809).

Further, since the continuous running distance during puncturing largely depends on the strength of the reinforcing rubber layer, in order to improve run-flat running performance, it is necessary to increase the thickness and rubber hardness of the reinforcing rubber layer. Required. However, when such a reinforcing rubber layer is formed firmly, there is a problem that the influence is exerted even at the time of normal running in which the internal pressure is filled, and the riding comfort is greatly impaired.

The present invention has been devised in view of the above-mentioned problems, and has a first rubber portion having a maximum thickness portion on the tread portion side and a maximum thickness portion on the bead portion side. And a second rubber portion having the following characteristics. The rubber hardness is limited in relation to the rubber hardness of the bead apex rubber. It is intended to provide a run flat tire that can travel a distance.

[0006]

According to a first aspect of the present invention, there is provided a carcass extending from a tread portion to a bead core of a bead portion via a sidewall portion, and a tire radius extending from an outer surface of the bead core in a tire radial direction. A run-flat tire comprising a bead apex rubber tapered and extending outward in the direction, and a side reinforcing rubber layer having a substantially crescent cross section disposed on the sidewall portion, wherein the side reinforcing rubber layer has a tread thereof. A first rubber portion having a maximum thickness portion on the side of the first rubber portion, and a second rubber portion having a maximum thickness portion on the side of the bead portion;
The run wherein the IS durometer hardness S1, the JIS durometer hardness S2 of the second rubber portion, and the JIS durometer hardness S3 of the bead apex rubber satisfy the relationship of S1 <S2, S3 ≦ S2. It is a flat tire.

The "JIS durometer hardness" is defined by JI
Defined as durometer hardness according to S-K6253.

According to a second aspect of the present invention, the carcass includes the side reinforcing rubber layer, a carcass ply extending outside the bead apex rubber in the tire axial direction, and a JIS durometer hardness of the first rubber portion. S
1, JIS durometer hardness S2 of the second rubber portion,
The run-flat tire according to claim 1, wherein the bead apex rubber and a JIS durometer hardness S3 satisfy a relationship of S1 <S2 and S3 <S2.

According to a third aspect of the present invention, the JIS durometer hardness S1 of the first rubber portion is 65 to 85 degrees, and the JIS durometer hardness S2 of the second rubber portion is 7 degrees.
0-95 degrees, and JI of the bead apex rubber
3. The run flat tire according to claim 1, wherein the S durometer hardness S3 is 65 to 85 degrees.

According to a fourth aspect of the present invention, the difference between the JIS durometer hardness S2 of the second rubber portion and the JIS durometer hardness S1 of the first rubber portion is (S2-S1).
The run-flat tire according to any one of claims 1 to 3, wherein the difference (S2-S3) between the bead apex rubber and the JIS durometer hardness S3 is 4 degrees or more.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings illustrating a runless tire for a tubeless passenger car. FIG. 1 shows a right half section of the tire meridian in a normal state in which the rim is assembled to the normal rim J and the normal internal pressure is filled and no load is applied, and the left section also appears almost symmetrically. The "regular rim" is a rim defined for each tire size in a standard system including the standard on which the tire is based. For example, a standard rim for JATMA, a "Design Rim" for TRA, or ET
If it is RTO, it will be "Measuring Rim". "Normal internal pressure" is the air pressure specified for each tire size in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure is used. For TRA, the table "TIRE LOAD LIMITS" is used. AT VARIOUS COLD INFLATION PRE
SSURES ", maximum value for ETRTO," INFLAT
ION PRESSURE ", but if the tire is for a passenger car, the pressure is 180 kPa. Hereinafter, unless otherwise specified, the dimensions of each part are specified in this normal state.

In the figure, a run flat tire 1 of the present embodiment includes a carcass 6 extending from a tread portion 2 to a bead core 5 of a bead portion 4 via a sidewall portion 3, a tire radially outside the carcass 6 and a tread portion 2. , A bead apex rubber 8 tapering outwardly from the tire radial outer surface of the bead core 5 to the outside, and in the present example, the side wall portion located on the tire inner surface side Side reinforcing rubber layer 1 disposed on 3
It has zero. An inner liner (not shown) made of rubber that is hardly permeable to air is disposed inside the side reinforcing rubber layer 10 in the tire axial direction.

The carcass 6 has a toroidal shape extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3. The carcass 6 is, in the present embodiment,
One formed from one carcass ply 6A is shown.

The carcass ply 6A is formed by coating carcass cords arranged in parallel with topping rubber. The carcass cord is preferably made of an organic fiber such as nylon, polyester, rayon, or aromatic polyamide. In the present embodiment, the carcass cords are arranged at an angle of 70 to 90 degrees, more preferably 80 to 90 degrees with respect to the tire equator C. Further, in this example, the carcass ply 6A has a main body 6a straddling between the bead cores 5 and 5 in a toroidal shape, and is continuous with both ends of the main body 6a and is turned around the bead core 5 from the inner side in the tire axial direction to the outer side. The bead apex rubber 8 is integrally provided with a folded portion 6b extending along the outer surface in the tire axial direction.

In this embodiment, the outer end 6be of the folded portion 6b of the carcass ply 6A terminates at a position inside the belt layer 7 in the tire radial direction and beyond the outer end 7e of the belt layer 7 in the tire axial direction. A so-called super high turn-up structure is illustrated. Thereby, the run flat tire 1 can effectively reinforce the sidewall portion 3 using one carcass ply 6A. Further, since the outer end 6be of the folded portion 6b is separated from the side wall portion 3 which is largely bent during puncturing, damage such as separation originating from the outer end 6be can be suitably suppressed and durability can be improved. The length EW in the tire axial direction of the overlapping portion between the folded portion 6b and the belt layer 7 is, for example, 5 mm or more,
It is preferably 10 mm or more, more preferably 15 to 25 mm.

The bead apex rubber 8 is formed of a rubber material which extends from the outer surface of the bead core 5 outward in the tire radial direction. The bead apex rubber 8 is useful for increasing the bending rigidity of the bead portion 4 and for suppressing longitudinal bending of the tire. The height h of the bead apex rubber 8 is set to 10 to 45%, more preferably 15 to 40% of the tire section height H. In this example, a tire provided with a rim protector 4a protruding from the bead portion 4 so as to cover the outer side of the rim flange JF in the tire radial direction is illustrated. Such a rim protector 4a can suppress excessive vertical bending of the tire side portion by abutting so as to cover the rim flange JF at the time of puncturing.

In the present embodiment, the belt layer 7 is formed by applying a highly elastic belt cord to the tire equator C by, for example, 10 to 3 times.
Two belt plies 7A and 7 arranged at an angle of about 5 °
B. The belt plies 7A and 7B are overlapped so that the belt cords cross each other. Thereby, the belt layer 7 strongly tightens the carcass 6 to increase the rigidity of the tread portion 2 and exerts an advantage as a radial tire. The belt cord is made of steel in this embodiment, but a highly elastic organic fiber cord such as aramid or rayon may be used if necessary.

The side reinforcing rubber layer 10 is formed in a substantially crescent-shaped cross section in which the thickness is gradually reduced from the thick central portion inward and outward in the tire radial direction. The side reinforcing rubber layer 10 of this example is, for example, one disposed inside the main body 6a of the carcass ply 6A in the tire axial direction. As a result, at the time of bending deformation of the side reinforcing rubber layer 10, the carcass ply 6A having a cord reinforces its tensile side. Thereby, the bending rigidity of the side reinforcing rubber layer 10 can be increased, and the longitudinal deflection of the tire during load running in a punctured state can be more effectively reduced. In addition, about bead apex rubber 8,
In this example, since the folded portion 6b of the carcass ply 6A is located on the outer side in the tire axial direction reaching the entire height, the bending rigidity can be improved similarly to the side reinforcing rubber layer 10.

If the length L in the tire radial direction of the side reinforcing rubber layer 10 is too small, the effect of suppressing longitudinal deflection during run flat running tends to be reduced. May worsen the performance. From such a viewpoint, the length L of the side reinforcing rubber layer 10
Is preferably set to, for example, about 35 to 85%, more preferably about 40 to 65% of the tire section height H. The side reinforcing rubber layer 10 has a maximum thickness tmax of 4
The maximum thickness at the maximum width position M of the tire is exemplified by a thickness of 20 to 20 mm, more preferably 5 to 15 mm. In this example, the inner end 10i of the side reinforcing rubber layer 10 is used.
The side overlaps the bead apex rubber 8 inside and outside in the tire axial direction. The overlap length K in the tire radial direction is, for example, about 3 to 45%, more preferably about 5 to 35% of the length L of the side reinforcing rubber layer 10 in order to reinforce the tire side portion in a well-balanced manner. It is desirable to do.

The side reinforcing rubber layer 10 of this embodiment has a first rubber portion 11 having a maximum thickness portion 11a having a maximum thickness t1 on the tread portion side and a maximum thickness t on the bead portion side.
It is composed of two layers of the second rubber portion 12 having the maximum thickness portion 12a of two.

In the present embodiment, the first rubber portion 11 has a thickness corresponding to the maximum thickness portion 11a and the inner and outer ends 11i and 11o in the tire radial direction. And end portions 11b and 11c. In this example, the maximum thickness portion 11a is located outside the tire maximum width position M in the tire radial direction. The maximum thickness t1 of the first rubber portion 11 is, for example, preferably 3 mm or more, more preferably 4 mm or more, and further preferably 5 to 10 mm. The thickness t1 is 3
If it is less than 10 mm, the reinforcing effect tends to decrease, and if it exceeds 10 mm, the ride comfort tends to be impaired at the time of internal pressure charging.

In the present embodiment, the second rubber portion 12 has the maximum thickness portion 12a and the inner and outer ends 12i and 12o of the tire in the tire radial direction. End portion 12 gradually reduced in thickness toward
b, 12c. In this example, the maximum thickness portion 12 a is located radially inward of the tire maximum width position M and outward of the outer end of the bead apex rubber 8.

The maximum thickness portion 12 of the second rubber portion 12
a is the first rubber portion 1 in the tire radial direction in this example.
1 is located at substantially the same height as the inner end 11i. Similarly, the maximum thickness portion 11a of the first rubber portion 11 is located at substantially the same height as the outer end 12o of the second rubber portion 12 in the tire radial direction. Thereby, the cross-sectional shape of the side reinforcing rubber layer 10 is the smooth crescent shape.

By the way, in the side region of the tire from the vicinity of the outer end 7e of the belt layer 7 to the bead core 5, the vicinity of the bead core 5 is supported by the flange JF of the rim J. Not necessary. In the vicinity of the outer end 7e of the belt layer 7, the belt layer 7 provided with the highly elastic belt cord shares the bending rigidity, so that similarly, a stronger reinforcement is not necessary. On the other hand, in the region inside the sidewall from the tire maximum width position M to the bead portion 4 side, deflection during run-flat running tends to concentrate, so it is important to reinforce this portion more intensively. In the present invention, in view of such a situation, JIS durometer hardness S1 of the first rubber portion 11, JIS durometer hardness S2 of the second rubber portion 12, and JIS of the bead apex rubber 8
The durometer hardness S3 is set so as to satisfy the relationship of S1 <S2, S3 ≦ S2, and more preferably to satisfy the relationship of S1 <S2, S3 <S2.

In the load running state where the normal internal pressure is charged, such a run flat tire 1 has a smaller deflection in the side wall inner region than the conventional run flat tire, and the end portion of the belt layer 7 In addition, the bending of the bead portion 4 near the outer portion of the bead core 5 increases. Thereby, the run flat tire of the present embodiment can disperse the strain widely in the side region as a whole. Therefore, the vertical spring of the tire can be lowered to contribute to the improvement of riding comfort.

In order to produce such an effect more effectively, the JIS durometer hardness S1, S3 of the first rubber portion 11 and the bead apex rubber 8 is preferably 65 to 85 degrees, more preferably. Is 65-80 degrees,
More preferably, it is desirably 65 to 75. When the hardness S1 or S3 is less than 65 degrees, there is a tendency that the effect of suppressing the vertical deflection at the time of puncturing is not sufficiently obtained.
Exceeding the degree tends to impair ride comfort during normal running, and also makes it easier to concentrate distortion in the central region of the side portion. The hardnesses S1 and S3 of the first rubber portion 11 and the bead apex rubber 8 may be the same or different.

The JIS durometer hardness S2 of the second rubber portion 12 is preferably 70 to 95 degrees, more preferably 75 to 90 degrees. When the hardness S2 is less than 70 degrees, the reinforcing effect in the side wall inner region where a large strain acts during run flat running becomes insufficient, and the run flat continuous running distance may be reduced. If it exceeds, not only does the reinforcing effect level off, but it also deteriorates the riding comfort during normal running.

In particular, the JIS durometer hardness S2 of the second rubber portion 12 is different from the JIS durometer hardness S1 of the first rubber portion 11 (S2-S1) and the JIS durometer hardness S3 of the bead apex rubber. Difference (S
2-S3) is preferably set to 4 degrees or more, more preferably 6 degrees or more, and further preferably about 6 to 12 degrees. As a result, the run-flat running performance and the riding comfort performance during normal running can be particularly well-balanced.

The end portion 12c of the second rubber portion 12 is
In the present example, the first rubber portion 11 is located inside the first rubber portion 11 in the tire axial direction. Accordingly, when a load is applied, tensile stress is applied to the first rubber portion 11 and compressive stress is applied to the second rubber portion 12. Due to the characteristics of the rubber material, a rubber having a high hardness is strong at the time of compression, and a rubber having a low hardness is strong at the tension side, so that a rubber material having a high hardness (the second rubber portion 12) is arranged inside the bend (compression side). This can increase durability.

On the other hand, the end portion 12c of the second rubber portion 12
May be located outside the first rubber portion 11 in the tire axial direction. In this case, since the first rubber portion 11 having low hardness is arranged on the compression side of bending, the amount of deformation of the entire tire with respect to a constant load increases, which helps to improve the ride comfort.

The length L1 of the first rubber portion 11 in the tire radial direction is set to, for example, about 20 to 70%, more preferably about 30 to 60% of the length L of the side reinforcing rubber layer 10. desirable. Similarly, the length L2 of the second rubber portion 12 in the tire radial direction is, for example, 50 to 90% of the length L of the side reinforcing rubber layer 10, and more preferably 60 to 80%.
% Is desirable. Thereby, the side reinforcing rubber layer 10 can more effectively prevent deterioration of the riding comfort during normal running while supporting the load during run flat running.

The first rubber portion 11 and the second rubber portion 12
Preferably, rubber having a small loss tangent tan δ (for example, tan δ <0.1) is suitably used, and it is preferable to suppress heat generation and improve durability. The measurement condition of tan δ is
70 using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho
C., frequency 10 Hz, dynamic strain rate 2%. Further, these rubbers may be blended with, for example, short fibers.
Although various types of short fibers can be used, short fibers made of organic fibers such as nylon, rayon, polyester, and aromatic polyamide are preferably used. By orienting the short fibers in a predetermined direction in the rubber (for example, in the tire circumferential direction or the tire radial direction), the elastic modulus and the like of the side reinforcing rubber layer 10 can be appropriately adjusted as required.

A pneumatic tire including such a run flat tire 1 is vulcanized using a mold. In FIG. 2, the outline K1 of the tire outer surface when vulcanization molding is performed with a general mold is indicated by a chain line. The solid line is the contour line K2 in a state where the molded tire is assembled on the rim and the internal pressure is filled. As is clear from the figure, the clip width CW, which is the width in the tire axial direction between the outer surfaces of the bead portions 4 during vulcanization molding, is usually set to be larger than the rim width RW of the regular rim J.

For this reason, when the tire is assembled on the rim and filled with internal pressure, distortion concentrates near the buttress portion 13 which is the outer portion of the sidewall portion 3, and the vicinity of the buttress portion 13 even during run flat running during puncturing. In many cases, structural damage of the tire occurs. Therefore, in the conventional run flat tire, it is necessary to reinforce the buttress portion 13 which is closely related to the ride comfort, and the ride comfort is likely to be deteriorated.

In the run flat tire 1 of the present embodiment, the clip width CW during vulcanization molding is changed to the rim width R of the regular rim J.
It shows what is manufactured by vulcanization molding with setting to be substantially equal to W. For this reason, even during the internal pressure filling, the distortion caused by the narrowing of the bead width causes the buttress portion 13
Since it is difficult to concentrate on the run, the distortion can be made uniform, and the run flat traveling distance can be more effectively increased. From this point of view, the clip width CW and the rim width RW of the regular rim J
(CR-RW) is preferably 0 to 25 mm, more preferably 0 to 15 mm.

The run flat tire 1 of the present embodiment
In the normal state, in the tire meridian section, the cross-sectional contour line 2e of the tire outer surface from the tread portion 2 to the sidewall portion 3 is, as shown in FIGS. Up to the tire maximum width position M, an involute curve G whose curvature radius R (x) gradually decreases from the tire equator point P toward the sidewall portion 3 is substantially formed. The involute curve G of the present example is such that the other end of the yarn wound around the basic ellipse V having one major axis (2 × b) and a minor axis (2 × a) (where a <b) in the tire radial direction. It is substantially formed by an involute curve G to be drawn.

The profile line 2e is formed symmetrically with respect to the tire equator C. Although not shown in FIG. 1, a tread groove for drainage or the like may be provided in the tread portion 2. In this case, when the cross-sectional contour line 2 e is specified, the gap between the groove edges in the tire meridian cross-section is smoothly changed. We will supplement the virtual extension line that was connected.

In general, the run-flat tire 1 provided with the side reinforcing rubber layer 10 has a cross-sectional profile 2e 'formed substantially flat from the tire equatorial point P to the vicinity of the tread edge as shown by a chain line in FIG. Therefore, the sidewall area of the tire is long. For this reason, in order to exhibit run flat performance, the area where the rubber reinforcing material constituting the side reinforcing rubber layer is arranged becomes longer, the tire tends to be heavier, the vertical spring becomes higher, and the riding comfort tends to be impaired. Become.

On the other hand, in the run flat tire 1 of the present embodiment, the cross-sectional contour 2e of the tire surface is substantially formed by the involute curve G as described above, so that the run-flat tire 1 extends along the cross-sectional contour 2e. The absolute distance from the tire equator point P to the tire maximum width position M is shorter than that of a conventional tire. In particular, since the side wall portion region is shortened, for example, the amount of rubber used in the side reinforcing rubber layer 10 is reduced, which is useful for lightly configuring a tire. Also tread part 2
The shape of the shape is very round, and the vertical springs are reduced, which helps to improve the riding comfort. In addition, since the radius of curvature gradually decreases from the tire equator point P toward the tread edge, the uniformity of the contact pressure can be further promoted.

As shown in FIG. 4, the basic ellipse V of the involute-shaped curve G is defined by a tire radial direction line passing through the tire equator point P of the cross-sectional contour line 2e in the tire meridian section, and the Y-axis and the cross-sectional contour. Tire equator point P of line 2e
In the xy coordinate system and the XY coordinate system in which the tire axis direction line passing through the center point of the curvature radius B
An example represented by an elliptic curve of the following formula (1) is illustrated. Such an involute curve G is formed by fixing one end to the origin O of the coordinate system and winding the other end of the yarn wound around the basic ellipse V. A (X, Y) will follow the locus drawn. (X−a) ² / a ² + y ² / b ² = 1 (1) (where | a | <| b | is a constant other than 0)

The sectional contour line 2e substantially using such an involute curve G is a radius of curvature B at the tire equatorial point P, a tire maximum width position M, and a tire sectional width which is a distance between the tire axial directions M. , The tire radial height h from the tire equator point P at the tire section height H and the tire maximum width position M, and the base ellipse so that the involute curve connects the tire equatorial point P and the tire maximum width position M. The minor axis of V (2 × a) is appropriately determined.

The expression "substantially" that the cross-sectional contour line 2e is formed by such an involute-like curve means that the mold processing accuracy in manufacturing a tire vulcanizing mold is taken into consideration. The present invention also relates to an embodiment in which the cross-sectional contour line 2e is approximately formed by a plurality of arcs, for example, a connected body of five or more arcs such that an error from the involute curve G is within ± 1/10 (mm). Can be included in the range. This is effective as an approximation method for obtaining a contour line that can be expected to have substantially the same action and effect even if the cross-sectional contour line 2e is not physically identical to the involute curve G.

Although not shown, the side reinforcing rubber layer 10 is coated with, for example, a fiber cord ply having excellent compression strain resistance on the inner side in the tire radial direction and has a tensile strain resistance on the outer side in the tire axial direction. It can also be formed by covering with an excellent cord ply, and in this case, the amount of rubber used for each of the first rubber portion 11 and the second rubber portion 12 can be reduced to reduce the weight of the tire. Although described in detail above, the present invention can be implemented in various forms without being limited to the exemplary embodiments.

[0044]

[Example] Based on the specifications in Table 1, the tire size was 205 /
Prototype 55R16 run flat tires,
The run flat performance, the vertical spring of the tire, etc. were measured.

<Run-flat performance> Regular rim (16 × 6 1 / 2JJ) with the valve core removed from the test tire
At a speed of 90 on the drum testing machine with the internal pressure set to 0.
The vehicle was run at km / H and a vertical load of 4.5 kN, and the running distance until the tire was broken was measured. The higher the value, the better.

<Vertical Spring of Tire> The test tire is assembled on a regular rim (16 × 6 1 / 2JJ) and the internal pressure is 200 kP.
The amount of vertical deflection when filling a and applying a vertical load of 4 kN is obtained, and the reciprocal of the amount of vertical deflection is indicated by an index with the comparative example being 100. The smaller the value is, the smaller the longitudinal spring constant is, and the more comfortable the ride is. Table 1 shows the test results and the like.

[0047]

[Table 1]

[0048]

As described above, the run flat tire of the present invention can increase the run flat continuous running distance without significantly deteriorating the riding comfort.

Further, when the hardness of each rubber portion is limited as in the inventions of claims 2 to 4, it is possible to more effectively balance the riding comfort and the run flat continuous traveling distance.

[Brief description of the drawings]

FIG. 1 is a right half sectional view of a run flat tire according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an outline of a tire outer surface.

FIG. 3 is a diagram illustrating a cross-sectional contour line and an involute-like curve of a tire.

FIG. 4 is a graph illustrating an involute curve.

FIG. 5 is a partial sectional view of a comparative example tire.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6a Body part 6b Folding part 7 Belt layer 10 Side reinforcing rubber layer 11 First rubber part 12 Second rubber part M Tire maximum width position H Tire section height

Claims (4)

[Claims] 1. A carcass extending from a tread portion to a bead core of a bead portion via a sidewall portion, a bead apex rubber tapering from a tire radially outer surface of the bead core to a tire radially outer side, and the sidewall portion. A run-flat tire comprising a side reinforcing rubber layer having a substantially crescent shape in cross-section, wherein the side reinforcing rubber layer has a first rubber portion having a maximum thickness portion on a tread side thereof, A second rubber portion having a maximum thickness portion on the bead portion side, and a JIS durometer hardness S1 of the first rubber portion.
JIS durometer hardness S2 of the second rubber portion, and JIS durometer hardness S2 of the bead apex rubber
3 satisfies the following relationships: S1 <S2, S3 ≦ S2. 2. The carcass comprises: the side reinforcing rubber layer;
A JIS durometer hardness S1 of the first rubber portion, a JIS durometer hardness S2 of the second rubber portion, and a JIS of the bead apex rubber. The run-flat tire according to claim 1, wherein the durometer hardness S3 satisfies the following relationships: S1 <S2, S3 <S2. 3. The JIS durometer hardness S1 of the first rubber part is 65 to 85 degrees, and the JIS durometer hardness of the second rubber part is 3.
The durometer hardness S2 is 70 to 95 degrees, and the bead apex rubber has a JIS durometer hardness S3 of 6 degrees.
The run flat tire according to claim 1 or 2, wherein the angle is 5 to 85 degrees. 4. The JIS durometer hardness S2 of the second rubber portion is different from the JIS durometer hardness S1 of the first rubber portion (S2-S1), and the JIS durometer hardness S3 of the bead apex rubber. (S2-S
3. The method according to claim 1, wherein 3) is at least 4 degrees.
The run flat tire according to any one of the above.