Pneumatic tire

Abstract

To provide a pneumatic tire improved in rolling resistance performance without impairing ride comfort performance.SOLUTION: The pneumatic tire has a tread portion 2. The tread portion 2 includes: a cord reinforcing layer 10 including a belt ply 7A; and a tread rubber 2G. A product T1×T2×La×tan δ 1 of a thickness T1 (mm) of the tread rubber 2G at a position of a tire equator C, an average thickness T2 (mm) of the one belt ply 7A, a land ratio La of a ground contact surface 2s, and a loss tangent tan δ 1 of the tread rubber 2G at 30°C, is 0.33 to 1.10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] Patent Document 1 listed below proposes a tire that is expected to improve rolling resistance when the vehicle starts moving by specifying the loss tangent of the cap rubber layer of the tread portion and the thickness of the tread portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7337333 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for improved fuel economy performance of vehicles, and a further reduction in the rolling resistance of tires mounted on vehicles. Known methods for reducing the rolling resistance of tires (hereinafter referred to as "improving rolling resistance performance") include reducing the volume of tread rubber or belt layers, and reducing the loss tangent of the tread rubber.

[0005] However, in all of the above methods, minute vibrations of the tire while the vehicle is running are easily transmitted to the vehicle, which may result in a loss of ride comfort.

[0006] The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire having improved rolling resistance performance without impairing ride comfort performance. [Means for solving the problem]

[0007] The present invention is a pneumatic tire having a tread portion, the tread portion including a cord reinforcement layer including at least one belt ply in which a plurality of steel cords are covered with a topping rubber, and tread rubber forming from the radially outer surface of the cord reinforcement layer to the contact surface of the tread portion, wherein the product T1·T2·La·tanδ1 of the thickness T1 (mm) of the tread rubber at the tire equator, the average thickness T2 (mm) of the one belt ply, the land ratio La of the contact surface, and the loss tangent tanδ1 of the tread rubber at 30°C is 0.33 to 1.10. [Effects of the Invention]

[0008] By adopting the above-described configuration, the pneumatic tire of the present invention can improve rolling resistance performance without impairing ride comfort performance. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the tread portion of FIG. 1. [Figure 3] FIG. 2 is a development view showing the cord arrangement of the cord reinforcement layer of FIG. 1. [Figure 4] FIG. 4 is a cross-sectional view of a steel cord according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described below with reference to the drawings. The drawings are intended to illustrate the features of the present invention, but may include exaggerated representations and representations that differ from the dimensional ratios of the actual structure to facilitate understanding of the present invention. Furthermore, identical or common elements are designated by the same reference numerals throughout the embodiments, and redundant explanations will be omitted. Furthermore, well-known configurations may be appropriately adopted for configurations not described in this specification.

[0011] FIG. 1 shows a cross-sectional view of a pneumatic tire 1 (hereinafter, sometimes simply referred to as "tire 1") according to one embodiment of the present invention. FIG. 1 is a cross-sectional view of the tire 1 in a normal state, taken along a tire meridian including the tire rotation axis. As shown in FIG. 1, the tire 1 according to this embodiment is suitable for use as a pneumatic tire for passenger cars, for example. However, the present invention is not limited to this embodiment, and may also be applied to a pneumatic tire for heavy loads, for example.

[0012] "Normal condition" means, in the case of a pneumatic tire for which various standards are established, a state in which the tire is mounted on a normal rim, inflated to the normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established, the normal condition means a standard use state according to the intended use of the tire, in which the tire is not mounted on a vehicle and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition. In addition, the dimensions of components that cannot be measured in the normal condition (for example, the internal materials of the tire 1) are values ​​measured with the tire 1 in a state as close to the normal condition as possible.

[0013] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

[0014] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0015] The tire 1 includes a tread portion 2, a first sidewall portion 3A, a second sidewall portion 3B, and a first bead portion 4A and a second bead portion 4B. The first sidewall portion 3A is connected to an axial first end portion 2a (the right end portion in each drawing in this specification) of the tread portion 2 and extends radially inward. The second sidewall portion 3B is connected to an axial second end portion 2b (the left end portion in each drawing in this specification) of the tread portion 2 and extends radially inward. The first sidewall portion 3A and the second sidewall portion 3B each include a tire maximum width position 1M. The first bead portion 4A is connected to the radially inward side of the first sidewall portion 3A. The second bead portion 4B is connected to the radially inward side of the second sidewall portion 3B.

[0016] The tire 1 includes a carcass 6. The carcass 6 extends from a first bead portion 4A, through a first sidewall portion 3A, a tread portion 2, and a second sidewall portion 3B, to a second bead portion 4B.

[0017] The carcass 6 is composed of, for example, one carcass ply 6A. The carcass ply 6A includes, for example, a main body portion 6a and a turned-up portion 6b. The main body portion 6a extends, for example, between the first bead portion 4A and the second bead portion 4B. The turned-up portion 6b is continuous with the main body portion 6a and is turned up around the bead core 5 from the inside to the outside in the tire axial direction.

[0018] The carcass ply 6A includes a plurality of carcass cords and a topping rubber covering the cords (not shown). The carcass cords are made of organic fiber cords such as aramid or rayon. The carcass cords are preferably arranged at an angle of 70 to 90 degrees relative to the tire equator C. That is, the tire 1 of this embodiment has a radial structure carcass.

[0019] In this specification, when a numerical range for various parameters is described, unless otherwise specified, the numerical range refers to the numerical range for the average value of the parameter. Therefore, the numerical range for the carcass cord angle described above refers to the numerical range of the average value of angles measured at various positions for multiple carcass cords. The same applies to other parameters described below.

[0020] Fig. 2 shows an enlarged cross-sectional view of the tread portion 2 of Fig. 1. As shown in Fig. 2, the tread portion 2 of this embodiment includes a cord reinforcing layer 10. The cord reinforcing layer 10 is disposed on the outer side of the carcass 6 (shown in Fig. 1) in the radial direction of the tire.

[0021] Fig. 3 shows a development view conceptually illustrating the cord arrangement of the cord reinforcement layer 10. As shown in Fig. 3, the cord reinforcement layer 10 of this embodiment includes at least one belt ply 7A in which a plurality of steel cords 12 are covered with a topping rubber 13. The cord reinforcement layer 10 of this embodiment is configured to include a belt layer 7 including the belt ply 7A, and a band layer 8.

[0022] The belt layer 7 of this embodiment includes two belt plies 7A laminated in the tire radial direction. In each of these belt plies 7A, steel cords 12 are arranged at an angle θ1 of 15 to 45° with respect to the tire circumferential direction. The steel cords 12 included in one belt ply 7A and the steel cords 12 included in the other belt ply 7A are inclined in opposite directions with respect to the tire circumferential direction. This effectively reinforces the tread portion 2.

[0023] The band layer 8 is composed of, for example, one band ply 8A. The band ply 8A includes, for example, band cords 8c arranged at an angle θ2 of 5° or less with respect to the tire circumferential direction, and a topping rubber 8g covering the band cords. The band layer 8 in this embodiment is arranged so as to cover the entire belt layer 7.

[0024] As shown in Fig. 2, the tread portion 2 includes a tread rubber 2G that forms from the radially outer surface of the cord reinforcing layer 10 to the contact surface 2s of the tread portion 2. In Fig. 2, the tread rubber 2G is hatched to look like it is made of a single layer of rubber, but the present invention is not limited to this. In other words, the tread rubber 2G may be made of multiple overlapping rubber layers.

[0025] The tread rubber 2G has a thickness T1 at the position of the tire equator C. When a circumferential groove 9 or the like is provided at the position of the tire equator C in the tread portion 2, the thickness T1 means the thickness in a hypothetical state in which the circumferential groove 9 is filled.

[0026] The tread rubber 2G has a loss tangent tanδ1 at 30°C. This loss tangent tanδ1 is measured under the following conditions using a viscoelasticity spectrometer in accordance with the provisions of JIS-K6394. The loss tangent tanδ1 means the average loss tangent of the tread rubber 2G at 30°C. Therefore, when the tread rubber 2G has multiple rubber layers, the average loss tangent of the loss tangents of the rubber layers at 30°C weighted by their volumes corresponds to the loss tangent tanδ1 of the tread rubber 2G. Initial distortion: 10% Amplitude: ±2% Frequency: 10Hz Deformation mode: tension Measurement temperature: 30℃

[0027] The ground contact surface 2s of the tread portion 2 is the surface that comes into contact with the road surface during normal running on the outer surface of the tread portion 2. The first tread edge Te1 and the second tread edge Te2 correspond to the boundaries between the ground contact surface 2s and the non-ground contact surface during normal running.

[0028] For pneumatic tires for which various standards are established, "normal load" refers to the load specified for each tire in the standard system including the standard on which the tire is based. For JATMA, this is "maximum load capacity," for TRA, this is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, this is "LOAD CAPACITY." For tires for which various standards are not established, "normal load" refers to the maximum load that can be applied when using the tire in accordance with the above standards.

[0029] The contact surface 2s of the tread portion 2 has a land ratio La. The land ratio La corresponds to the ratio of the actual contact area to the hypothetical contact area in a state where all grooves, sipes, recesses, etc. provided in the contact surface 2s are filled. In FIG. 2, only a plurality of circumferential grooves 9 extending continuously in the tire circumferential direction are shown as grooves provided in the contact surface 2s of the tread portion 2, but it goes without saying that lateral grooves extending in the tire axial direction may also be provided in the contact surface 2s of the tread portion 2 (not shown). Note that the specific arrangement of these grooves is not particularly limited in the present invention.

[0030] In the present invention, the product T1·T2·La·tanδ1 of the thickness T1 (mm) of the tread rubber 2G at the tire equator C, the average thickness T2 (mm) of one belt ply 7A, the land ratio La of the contact patch 2s, and the loss tangent tanδ1 of the tread rubber 2G at 30°C is 0.33 to 1.10. As a result, the tire 1 of the present invention can improve rolling resistance performance without impairing ride comfort performance. The reason for this is as follows.

[0031] The above-mentioned parameters can be determined independently. Meanwhile, among the above-mentioned parameters, the smaller the values ​​of the thickness T1, the thickness T2, and the land ratio La, the more the tire weight can be reduced and the more the rolling resistance performance can be improved. Furthermore, the smaller the value of the loss tangent tanδ1, the more the energy loss during tire rotation can be reduced and the more the rolling resistance performance can be improved. In other words, due to the above-mentioned mechanism, the smaller the value of each of the above-mentioned parameters, the more the rolling resistance performance can be expected to be improved. However, the smaller the value of each of the above-mentioned parameters, the more easily minute vibrations of the tire when the vehicle is running are transmitted to the vehicle, which may impair ride comfort.

[0032] Conversely, if the values ​​of the above-mentioned parameters (ie, thickness T1, thickness T2, land ratio La, and loss tangent tanδ1) are large, an improvement in ride comfort can be expected, but rolling resistance performance may be impaired.

[0033] The inventors investigated the degree of change between each of the above-mentioned parameters and rolling resistance performance and ride comfort performance. As a result, they found that, at least within the numerical range in which each of the above-mentioned parameters can be used in a normal tire (hereinafter referred to as the "usable range"), the transient characteristics of rolling resistance performance and ride comfort performance are similar between each of the above-mentioned parameters. Furthermore, as a result of more detailed investigation, they found that the degree of similarity is quite high, and that even if each parameter is multiplied and treated as a single parameter, there is no problem in defining rolling resistance performance and ride comfort performance.

[0034] Based on the above findings, in the present invention, by specifying the above-mentioned product T1·T2·La·tanδ1 in the range of 0.33 to 1.10, it is possible to improve rolling resistance performance without impairing ride comfort performance. Note that if the product T1·T2·La·tanδ1 is less than 0.33, tire vibrations become more noticeable to the driver, and ride comfort deteriorates. Also, if the product T1·T2·La·tanδ1 is greater than 1.10, ride comfort performance is maintained, but improvement in rolling resistance performance cannot be expected.

[0035] In the present invention, the thickness T1 can be within a range of 7 to 15.5 mm. The thickness T2 can be within a range of 0.5 to 2.0 mm. The land ratio La can be within a range of 0.40 to 0.95. The loss tangent tanδ1 can be within a range of 0.10 to 0.30. In the present invention, the above-described effects can be expected at least when each parameter is within the above-described range.

[0036] The following describes the configuration of this embodiment in more detail. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-described effects even if it does not include the configurations described below. Furthermore, even if any one of the configurations described below is applied alone to the tire 1 of the present invention having the above-described characteristics, an improvement in performance corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, an improvement in combined performance corresponding to those configurations can be expected.

[0037] In a more desirable embodiment, it is desirable that the various parameters be specified so that the above-mentioned product T1·T2·La·tan δ1 falls within the range of 0.50 to 1.00, thereby ensuring the above-mentioned effects.

[0038] The same effects can be expected even if the numerical range of the above-mentioned product T1·T2·La·tanδ1 is specified excluding the thickness T2. From this viewpoint, the product T1·La·tanδ1 of the thickness T1 (mm), the land ratio La, and the loss tangent tanδ1 is preferably 0.51 to 1.12.

[0039] The loss tangent tanδ1 is preferably 0.12 or more, more preferably 0.14 or more, and is preferably 0.22 or less, more preferably 0.20 or less, thereby optimizing the heat generation in the tread portion 2, reliably maintaining ride comfort, and also reducing road noise.

[0040] The land ratio La is preferably 0.60 or more, more preferably 0.64 or more, and is preferably 0.78 or less, more preferably 0.68 or less, thereby achieving a good balance between ride comfort and rolling resistance.

[0041] From the same viewpoint, the thickness T1 is preferably 9.0 mm or more, more preferably 9.5 mm or more, and is preferably 12.0 mm or less, more preferably 11.6 mm or less, although the present invention is not limited to such an embodiment.

[0042] The thickness T2 is, for example, preferably 1.20 mm or less, more preferably 1.00 mm or less. In a more preferable aspect, the thickness T2 of this embodiment is 0.66 to 0.98 mm. In this embodiment, the thickness T2 of each of the two belt plies 7A is set to be within the above range. The belt layer 7 formed of such belt plies 7A can achieve a lightweight design while exerting a reinforcing effect on the tread portion 2, and reliably improves rolling resistance performance.

[0043] From the same viewpoint, the weight per unit area of ​​one belt ply 7A is 1350 to 1980 g / m 2 The weight of the topping rubber contained per unit area of ​​one belt ply 7A is preferably 600 to 1300 g / m2 It is desirable that:

[0044] As shown in FIG. 3, one belt ply preferably includes 40 to 60 steel cords 12 per 5 cm width (width in the direction perpendicular to the longitudinal direction of the steel cords 12).

[0045] The steel cord 12 may be made of, for example, a so-called ST material (super tensile material) that can be expected to have a tensile strength of 3600 MPa or more, a so-called UT material (ultra tensile material) that can be expected to have a tensile strength of 4000 MPa or more, or a so-called MT material (mega tensile material) that can be expected to have a tensile strength of 4500 MPa or more. Therefore, the carbon content of the steel cord 12 is preferably 0.79% to 1.00%. However, the steel cord 12 of the present invention is not limited to this embodiment. The tensile strength may be measured by a known method.

[0046] The strength of each steel cord 12 is preferably 350 to 540 N. The outer diameter of the steel cord 12 is preferably 0.22 to 0.55 mm. This allows the tire to be lightweight and improves rolling resistance performance while ensuring the reinforcing effect of the belt layer 7 on the tread portion 2. The strength is measured by a well-known method, but if necessary, a measurement method in accordance with JIS G3510 may be adopted.

[0047] The steel cord 12 of this embodiment has, for example, a 1x1 structure made of monofilaments (not shown). The outer diameter of the monofilaments is, for example, 0.30 to 0.50 mm. However, the present invention is not limited to this embodiment.

[0048] Fig. 4 shows a cross-sectional view of a steel cord 12 in another embodiment. As shown in Fig. 4, the steel cord 12 may have a 1 x n structure made up of a plurality (n) of filaments 15. Fig. 4 shows a steel cord 12 with a 1 x 4 structure. The outer diameter D1 of each of the plurality of filaments 15 is, for example, 0.15 to 0.30 mm. This improves ride comfort and rolling resistance in a well-balanced manner.

[0049] Although a tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and practiced in various aspects. [Example]

[0050] Pneumatic tires of size 205 / 55R16 having the basic structure shown in Figure 1 were prototyped based on the specifications in Tables 1 and 2. As Comparative Examples 1 to 4, tires were prototyped in which the products T1·T2·La·tanδ1 were outside the numerical ranges specified in the present invention. The tires of Comparative Examples 1 to 4 were substantially the same as the tires of the Examples, except for the above-mentioned points. The rolling resistance performance and ride comfort performance of each test tire were tested. The common specifications and test methods for each test tire are as follows: Mounted rim: 16 x 6.5 Tire pressure: 250kPa Test vehicle: 2000cc, FF vehicle

[0051] <Rolling resistance performance> The rolling resistance of each test tire was measured using a rolling resistance tester. The results were expressed as an index of the measured rolling resistance, with a smaller value indicating a smaller rolling resistance.

[0052] <Ride comfort> The test tires were mounted on all wheels of a test vehicle, and the vehicle was driven on a test course, and the ride comfort was evaluated by the driver. The results were expressed as a score, with a higher score indicating better ride comfort.

[0053] The test results are shown in Tables 1-2.

[0054] [Table 1]

[0055] [Table 2]

[0056] As shown in Tables 1 and 2, Comparative Examples 1 and 2 have a large product T1·T2·La·tanδ1, resulting in rolling resistance performance of 8.1 to 8.6 points. On the other hand, Comparative Examples 3 and 4 have a small product T1·T2·La·tanδ1, resulting in improved rolling resistance performance but a ride comfort performance of 45 points. In contrast, it can be seen that Examples 1 to 20, by defining the product T1·T2·La·tanδ1 within a specific range, maintain a high ride comfort performance of 55 to 70 points while improving rolling resistance performance by 6.2 to 7.3 points. In other words, it was confirmed that the tires of the present invention have improved rolling resistance performance without impairing ride comfort performance.

[0057] [Note] The present invention includes the following aspects.

[0058] [Invention 1] A pneumatic tire having a tread portion, The tread portion includes a cord reinforcement layer including at least one belt ply in which a plurality of steel cords are covered with a topping rubber, and tread rubber that forms from the outer surface of the cord reinforcement layer in the tire radial direction to the contact surface of the tread portion, a product T1·T2·La·tanδ1 of a thickness T1 (mm) of the tread rubber at the tire equator, an average thickness T2 (mm) of one belt ply, a land ratio La of the contact surface, and a loss tangent tanδ1 of the tread rubber at 30°C is 0.33 to 1.10; Pneumatic tires. [Invention 2] The pneumatic tire according to invention 1, wherein the thickness T2 is 0.66 to 0.98 mm. [Invention 3] 3. The pneumatic tire according to claim 1 or 2, wherein the product T1·La·tanδ1 of the thickness T1 (mm), the land ratio La, and the loss tangent tanδ1 is 0.51 to 1.12. [Invention 4] The tire has a radial structure carcass that includes multiple carcass cords arranged at an angle of 70 to 90 degrees relative to the tire equator. 4. The pneumatic tire according to any one of claims 1 to 3, which is for a passenger car. [Invention 5] The cord reinforcement layer includes a belt layer formed by laminating two of the belt plies, and a band layer disposed on the outer side of the belt layer in the tire radial direction, 5. The pneumatic tire according to any one of claims 1 to 4, wherein the band layer includes a band cord oriented at an angle of 5° or less with respect to the circumferential direction of the tire. [Invention 6] 6. The pneumatic tire according to any one of claims 1 to 5, wherein the steel cord has an outer diameter of 0.22 to 0.55 mm. [Invention 7] The steel cord has a 1x1 structure made of monofilaments, 7. The pneumatic tire according to any one of Inventions 1 to 6, wherein the monofilament has an outer diameter of 0.30 to 0.50 mm. [Invention 8] The steel cord has a 1×n structure consisting of a plurality (n) of filaments, 8. The pneumatic tire according to any one of claims 1 to 7, wherein the outer diameter of each of the plurality of filaments is 0.15 to 0.30 mm. [Invention 9] 9. The pneumatic tire according to any one of Inventions 1 to 8, wherein the strength of one of the steel cords is 350 to 540N. [Invention 10] 10. The pneumatic tire according to any one of claims 1 to 9, wherein the carbon content of the steel cord is 0.79% to 1.00%. [Invention 11] 11. The pneumatic tire according to any one of claims 1 to 10, wherein one belt ply includes 40 to 60 steel cords per 5 cm width. [Explanation of symbols]

[0059] 2 Tread section 2s ground plane 2G tread rubber 12 Steel Cord 13 Topping Rubber 7A Belt Ply 10 Cord reinforcement layer T1 Thickness of tread rubber at the tire equator T2 Average thickness of one belt ply La Land ratio of the contact surface of the tread tanδ1 Loss tangent of tread rubber at 30°C

Claims

1. A pneumatic tire having a tread portion, The tread portion includes a cord reinforcement layer including at least one belt ply in which a plurality of steel cords are covered with a topping rubber, and a tread rubber that forms from the outer surface of the cord reinforcement layer in the tire radial direction to the ground contact surface of the tread portion, a product T1·T2·La·tanδ1 of a thickness T1 (mm) of the tread rubber at the tire equator, an average thickness T2 (mm) of one belt ply, a land ratio La of the contact surface, and a loss tangent tanδ1 of the tread rubber at 30°C is 0.33 to 1.10; Pneumatic tires.

2. 2. The pneumatic tire according to claim 1, wherein the thickness T2 is 0.66 to 0.98 mm.

3. 3. The pneumatic tire according to claim 2, wherein a product T1·La·tan δ1 of the thickness T1 (mm), the land ratio La, and the loss tangent tan δ1 is 0.51 to 1.

12.

4. The tire has a radial structure carcass including a plurality of carcass cords arranged at an angle of 70 to 90 degrees with respect to the tire equator, The pneumatic tire according to claim 3, which is for a passenger car.

5. the cord reinforcement layer includes a belt layer formed by laminating two of the belt plies, and a band layer disposed on the outer side of the belt layer in the tire radial direction, The pneumatic tire according to claim 4 , wherein the band layer includes a band cord oriented at an angle of 5° or less with respect to the tire circumferential direction.

6. 6. The pneumatic tire according to claim 1, wherein the steel cord has an outer diameter of 0.22 to 0.55 mm.

7. The steel cord has a 1x1 structure made of monofilaments, 6. The pneumatic tire according to claim 1, wherein the monofilament has an outer diameter of 0.30 to 0.50 mm.

8. The steel cord has a 1×n structure consisting of a plurality (n) of filaments, 6. The pneumatic tire according to claim 1, wherein the outer diameter of each of the plurality of filaments is 0.15 to 0.30 mm.

9. The pneumatic tire according to any one of claims 1 to 5, wherein a strength of one of the steel cords is 350 to 540N.

10. The pneumatic tire according to any one of claims 1 to 5, wherein the steel cord has a carbon content of 0.79% to 1.00%.

11. 6. The pneumatic tire according to claim 1, wherein one belt ply includes 40 to 60 steel cords per 5 cm width.

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