JP3482033B2 - Pneumatic tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of reducing pattern noise while maintaining wet running performance.

[0002]

2. Description of the Related Art Generally, a tread surface of a tire is provided with a vertical main groove extending in the tire circumferential direction and a lateral groove intersecting with the main groove for the purpose of imparting wet grip performance. However, the lateral groove induces pattern noise due to the pressure wave when the air in the groove repeats compression / opening (pumping) at the time of grounding, and this pattern noise causes the sound energy at a frequency corresponding to the pattern pitch of the lateral groove. The peak appears.

Therefore, conventionally, in order to reduce the pattern noise, the pattern pitch is improved to disperse the sound energy over a wide frequency band, and the groove volume of the lateral groove is reduced.
The pressure wave itself is being reduced. The reduction of the groove volume is achieved by suppressing the collapse of the block or the like into the groove at the time of ground contact by increasing the pattern rigidity in the circumferential direction, and by reducing the volume change of the groove in pumping. It can reduce itself.

[0004]

However, such reduction in groove volume not only impairs drainage performance, but also enhances pattern rigidity in the tire axial direction.
As shown in an exaggerated manner in FIG.
When the lateral force F is applied to the tread, the ground contact shape S1 changes in the direction in which one side a of the tread floats up from the road surface, resulting in a reduction in the ground contact area or an uneven distribution of the ground contact pressure, thus impairing the ground contact property. As a result, especially on a wet road surface or the like having a small coefficient of friction, there is a problem that grip performance becomes insufficient and weight running performance is significantly reduced.

The present invention is based on the fact that a lateral groove is formed of a shallow bottom portion and a deep bottom portion, and that the groove bottom of the shallow bottom portion is subjected to siping, so that necessary drainage is maintained and the circumference of the tread pattern is maintained. An object of the present invention is to provide a pneumatic tire capable of increasing the rigidity in the direction and relaxing the rigidity in the tire axial direction and solving the above problems.

[0006]

In order to achieve the above object, the invention according to claim 1 of the present invention (the present invention) is to provide two or more vertical main grooves extending in the tire circumferential direction in the tread portion. The tread portion is divided into a rib area on the shoulder side formed between the outermost vertical main groove in the tire axial direction and the tread contact edge, and a rib area between grooves formed between the vertical main grooves, and at least the shoulder side. In the rib area, lateral grooves that divide each rib area to form blocks lined up in the circumferential direction are provided, and the lateral groove has a groove depth D1 of 0.2 of the vertical main groove forming the rib area into which the lateral groove is divided. Depth D2 more than twice and less than 0.6 times
And a deep bottom portion having a depth D3 greater than 0.6 times and less than or equal to 0.6 times the groove depth D1 of the vertical main groove, and the groove bottom of the shallow bottom portion. The groove length L2 in the tire axial direction is set to 0.2 times or more and 1.0 times or less than the groove length L1 in the tire axial direction at the groove bottom of the lateral groove. , The groove length L
A pneumatic tire provided with siping having a length L3 in the tire axial direction that is 0.5 times or more and 0.8 times or less than 2.

[0007]

The horizontal groove formed of the shallow bottom portion and the deep bottom portion is more effective in increasing the pattern rigidity than the groove of the flat bottom having the same groove volume as the horizontal groove. The pattern noise can be reduced by suppressing the inward collapse and reducing the volume change in the pumping. Further, the lateral groove can suppress air column resonance in the lateral groove due to the height change of the groove bottom, which can also improve the noise performance.

Further, the siping arranged on the groove bottom of the shallow bottom portion closes the siping width against the external force in the circumferential direction, so that the pattern rigidity in the circumferential direction can be maintained and the effect of reducing the pattern noise can be maintained. sell. Further, since the siping does not restrain the movement of the rubber in the direction along the siping, the pattern rigidity in the tire axial direction can be relaxed. As a result, it is possible to suppress the reduction of the contact area and make the distribution of the contact pressure uniform, especially during turning, so that the contact performance can be improved and the wet running performance can be maintained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the figure, a pneumatic tire 1 includes a vertical main groove M that divides a tread portion 2 into a rib area 10 on the shoulder side and a rib area 11 between vertical main grooves, and at least each rib area 1 on the shoulder side.
A lateral groove Y for dividing 0 and 10 into blocks B is provided, and the siping 20 is provided on the groove bottom 15S of the shallow bottom portion 15 of the lateral groove Y.

In FIG. 2, the pneumatic tire 1 is JATM.
It is attached to the standard rim R determined by the standard such as A and JA
FIG. 3 is a meridional cross-sectional view showing a standard state when an internal pressure of 80% of the maximum internal pressure determined by standards such as TMA is filled, and the pneumatic tire 1 extends from the tread portion 2 to the sidewall portion 3 and then to the bead portion 4 In this example, the flat tire is formed as a passenger car radial tire having a carcass 6 whose both ends are folded back around the bead core 5. A tough belt layer 7 is arranged on the outer side of the carcass 6 in the radial direction.

In the carcass 6, the carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire equator C 1.
More than one carcass ply 6A, 6
As the carcass cord, a cord of organic fiber such as nylon, polyester or aromatic polyamide is preferably used. The folded-back portion of the inner carcass ply 6A covers the folded-back portion of the outer carcass ply 6B and ends near the maximum width position of the tire to relieve stress concentration on the ply end and to increase tire lateral rigidity.

The belt layer 7 comprises one or more belt cords arranged at an angle of 5 to 30 degrees with respect to the tire equator C, and in this example, two inner and outer belt plies 7A and 7B. It has a hoop effect to reinforce the tire and increase tread rigidity. The belt plies 7A and 7B are arranged so that the belt cords cross each other between the plies. As the belt cords, for example, steel cords and cords of the above-mentioned organic fibers are appropriately used in accordance with the required tire performance. .

On the outer side in the radial direction of the belt layer 7,
A band layer 9 is provided to cover at least the outer end of the belt layer 7 in the axial direction of the tire and to suppress the lifting.

As shown in FIG. 1, the tread portion 2 is formed with a block type or block rib type tread pattern having the vertical main groove M and the horizontal groove Y, in this example, a block rib type tread pattern. To be done.

The vertical main groove M forming this tread pattern
In this example, the vertical main grooves M1 and M on both sides of the tire equator C are
1 and the outer longitudinal main grooves M2, M2 arranged on the outside thereof
The tread portion 2 is made of a book and extends continuously in the tire circumferential direction, so that the tread portion 2 extends in the shoulder side rib area between the outer vertical main groove M2 which is the outermost side in the tire axial direction and the tread contact edge E. The rib regions 11A and 11A between the inner and outer vertical main grooves M1 and M2 and the rib region 11B between the inner vertical main grooves M1 and M1 are divided.

Each of the vertical main grooves M1 and M2 is, for example, a substantially straight groove having a constant groove depth. In this example, the groove depth D1a of the vertical main groove M1 is equal to that of the vertical main groove M2. It is substantially larger than the depth D1b. Each groove depth D1a, D1b is 6-10mm
However, the groove depths D1a and D1b may be set to be equal, and the groove depths D1a and D1b will be collectively referred to as the groove depth D1 below. The vertical main grooves M each have a groove width WM on the tread surface of about 5 to 12 mm.

Further, in the present application, the tread contact edge E is a contact point where the tread surface comes into contact with the tire in the standard condition under a standard load condition in which a load of 80% of the maximum load determined by the standards such as JATMA is applied. It is defined as the outer edge of the ground area in the axial direction of the tire.

The lateral groove Y is a groove width WY on the tread surface.
Is smaller than the groove width WM of the vertical main groove M, for example, about 3 mm, and includes at least shoulder side lateral grooves Y1 respectively arranged in the shoulder side rib regions 10 and 10.

In this example, the lateral groove Y comprises the lateral groove Y1 on the shoulder side and the lateral groove Y2 between the grooves arranged in the rib regions 11A, 11A between the grooves, and each lateral groove Y1, Y2 is respectively provided. By crossing the rib areas 10 and 11A, the rib areas 10 and 11A are divided into a plurality of blocks B1 and B2. The rib region 11B is, in this example, the inner vertical main groove M1.
It is formed as a rib body that has a notch portion 12 that extends from the inside and has an inner end that is interrupted in the vicinity of the tire equator C.

The lateral groove Y1 on the shoulder side is shown in FIG.
As shown in the enlarged view of FIG.
Shallow bottom portion 15 provided with Sipe 20 and groove bottom 16
S is formed from a deep deep bottom portion 16.

The lateral groove Y1 is formed by the tread ground edge E.
From the position of the buttress portion 17 on the upper end of the sidewall portion 3
It is connected to the extended portion 13 extending up to and therefore the lateral groove Y1 is
Both ends are formed as part of a groove body that is open at the outer vertical main groove M2 and the buttress portion 17, respectively.

The shallow bottom portion 15 is the groove bottom 15 in this example.
One end of S has a main portion 15A extending from the vertical main groove M2 substantially parallel to the tread surface, that is, having a substantially constant groove depth and extending outward in the tire axial direction. The main portion 15A has a shallow bottom portion. It is preferably formed over 80% or more, and more preferably over 90%.

The deep bottom portion 16 is the groove bottom 16 in this example.
The main portion 1 extends inward in the tire axial direction substantially in parallel with the main portion 15A with one end of S starting from the position of the tread contact edge E.
With 6A. Since the radius of curvature of the profile of the tread surface is greatly reduced in the vicinity of the tread ground contact edge E, in this example, the groove depth of the deep bottom portion 16 is gradually reduced toward the tread end side accordingly. There is.

In the present example, the reason for forming the shallow bottom portion 15 adjacent to the vertical main groove M2 is that the ground edge E is as described above.
This is because the radius of curvature in the vicinity is greatly reduced, and when the shallow bottom portion 15 is provided on the tread end side, the shallow bottom portion 15 tends to be lost early due to abrasion and drainage tends to be impaired. .

Each of the main parts 15A and 16A has a deep bottom part 16
The main portion 16A is connected to the main portion 16A through a connecting portion 19 that smoothly extends. Therefore, in this example, the upper portion 19A of the connecting portion 19 and the main portion 15A constitute the shallow bottom portion 15 and the lower portion 19B. A deep bottom portion 16 is constituted by the main portion 16A.

Here, the radial groove depth D2 of the shallow bottom portion 15 is not less than 0.2 times and not more than 0.6 times the radial groove depth D1 of the outer longitudinal main groove M2. Further, the groove depth D3 in the radial direction of the deep bottom portion 16 is set to be larger than 0.6 times and not larger than 1.0 times the groove depth D1.

Further, the construction length L2 in the tire axial direction at the groove bottom 15S of the shallow bottom portion 15 is 0.2 times or more the construction length L1 in the tire axial direction at the groove bottom of the lateral groove Y1 and 1.
It is less than 0 times.

The groove depth D2 and the groove depth D3 are generic names of the groove depth including the maximum groove depth and the minimum groove depth in the shallow bottom portion 15 and the deep bottom portion 16, respectively. Therefore, the shallow part 1
5 has maximum and minimum groove depths, the maximum and minimum groove depths are included in the range of 0.2 × D1 to 0.6 × D1, respectively. Similarly, when the deepest portion 16 has the maximum and minimum groove depths, the maximum and minimum groove depths are 0.6 × D1.
To 1.0 × D1.

The upper portion 19A and the lower portion 19B of the connecting portion 19 are divided by a depth position of 0.6 × D1 from the tread surface.

As described above, the lateral groove Y1 is formed in the shallow bottom portion 15
By forming it as a step groove composed of the deep bottom portion 16 and the deep bottom portion 16, it is possible to effectively increase the rigidity of the rib region 10 in the circumferential direction while maintaining a relatively high drainage property, reduce pattern noise, and reduce dryness. It is possible to improve the steering stability on the road surface.

Further, in this example, the siping 20 of the shallow bottom portion 15 is a fine groove or a cut groove extending along the groove center of the shallow bottom portion 15 in a direction intersecting with the tire circumferential direction. By closing the wall, the rigidity in the tire circumferential direction is maintained. Therefore, the siping width of the siping 20 is preferably 2.0 mm or less, more preferably 1.
6 mm or less, and the siping width is siping 20.
0.5mm or more is required when molding with a vulcanization mold, but when machine cutting with a cutter etc., it is practically 0mm
Can be

The siping 20 is the siping 20.
Since the movement of the rubber in the longitudinal direction of the tire can be enhanced, the pattern rigidity in the tire axial direction can be moderated moderately, and the ground contact can be greatly improved. Therefore, the length L3 of the groove bottom 15S of the siping 20 in the tire axial direction needs to be 0.5 times or more and 0.8 times or less the groove length L2 of the shallow bottom portion 15, and In this example, the siping 20 has one end opened by the vertical main groove M2 and is formed to have a substantially constant depth from the groove bottom 15S. The radial depth d of the siping 20 is equal to the difference (D1-D) between the groove depths D1 and D2.
It is preferably 0.3 times or more and 1.0 times or less than 2).

The effects of the stepped lateral groove Y2 and the siping 20 as described above are shown in FIG. 4, FIG. 5, FIG. 6, and FIG.
It can also be confirmed by the test results shown in. In each test, a tire of tire size 205 / 60R15 shown in FIGS. 1 to 3 was assembled on a standard rim R (15 × 6JJ) and filled with internal pressure (2.0 kg / cm ² ), and then FR of 2000 cc was obtained.
This is due to running in an actual vehicle mounted on a vehicle.

In FIG. 4, L1 = 28 mm (constant), L2 =
17mm (constant), D1 = 8.0mm (constant), main part 16A
Ratio D2 / D when the maximum groove depth D3 is 7.0 mm (constant) and the groove depth D2 in the main portion 15A is changed.
1 shows the relationship between 1 and the wet running performance and pattern noise during turning. The siping 20 is excluded from the lateral groove Y1. As shown in the figure, when the ratio D2 / D1 is less than 0.2, the drainage performance deteriorates and the pattern rigidity becomes excessive, so that the wet running performance becomes insufficient. When it is larger than 0.6, the pattern rigidity is too small to reduce the pattern noise. Therefore, D2 / D1 is preferably 0.4 or more and 0.6 or less.

In the wet running test, the vehicle was used to run at a limit speed on a paved circular circuit surface with a water depth of 3 mm and a radius of curvature of 60 m, and the lateral acceleration (lateral G) at that limit speed was calculated. , The average value is compared by index for each tire. The larger the index value, the better.

To test for pattern noise, the vehicle was run on a dry paved road surface with the engine off and a microphone was set at a position 7.5 m laterally from the vehicle.
The noise is measured according to ASO standard C-606, and the sound pressure at that time is compared with each other exponentially for each tire. The larger the index value, the better.

FIG. 5 shows that L1 = 28 in the tire.
mm (constant), D1 = 8.0 mm (constant), the groove depth D2 in the main portion 15A is D2 = 4.0 mm (constant), and the maximum groove depth D3 in the main portion 16A is D3 = 7.0 mm (constant), and L2
The relationship between the ratio L2 / L1 and the dry maneuverability and the pattern noise when V is changed is shown. The siping 20 is excluded from the lateral groove Y1. As shown in the figure, the ratio L2 / L
When 1 is less than 0.2, the pattern rigidity becomes too small to reduce the pattern noise, and the dry maneuverability also deteriorates. Moreover, further reducing pattern noise, in order to improve the dry steering resistance, the ratio L2 / L1 is laid further <br/> preferred is 0.4 or more, is set to 1 or less. When the ratio is larger than 0.7, the drainage becomes insufficient, and therefore the ratio L2 is more preferable.
/ L1 is 0.7 or less.

The dry controllability was evaluated by the 10-point method by the feeling of the driver when the vehicle was running on a dry pavement surface, and the larger the value, the better.

FIG. 6 shows that L1 = 28 in the tire.
mm (constant), L2 = 17 mm (constant), D1 = 8.0 mm
(Constant), groove depth D2 in the main portion 15A = 4.0 mm
(Constant), maximum groove depth D3 in the main portion 16A = 7.
The relationship between the ratio L3 / L2 when 0 mm (constant), d = 3.0 mm (constant) and L3 is changed, and the wet running performance and pattern noise during turning is shown. As shown in the figure, the circumferential rigidity of the pattern is maintained and the pattern noise can be maintained at a low value regardless of the presence or absence of the siping 20 and the ratio of the length L3 thereof. However, when the ratio L3 / L2 is less than 0.5, the effect of relaxing the rigidity in the tire axial direction becomes insufficient and the ground contact property deteriorates. When it is larger than 0.8, the cornering power tends to be insufficient when running on a dry road surface. Therefore, the range of 0.5 or more and 0.8 or less is set.
There is.

FIG. 7 shows that L1 = 28 in the tire.
mm (constant), L2 = 17 mm (constant), L3 = 10 mm (constant), D1 = 8.0 mm (constant), groove depth D2 = 4.0 mm (constant) in main part 15A, maximum in main part 16A The relationship between the ratio d / (D1-D2) when the groove depth D3 is 7.0 mm (constant) and d is changed, and the wet running performance and pattern noise during turning is shown. As shown in the figure, the pattern noise can be maintained at a low value regardless of the presence or absence of the siping 20 and the ratio of the depth d thereof. But the ratio d
When / (D1-D2) is less than 0.3, the effect of relaxing the rigidity in the tire axial direction becomes insufficient, the ground contact property deteriorates, and the wet running performance deteriorates. Further, when it is greater than 1.0, that is, when the bottom of the siping 20 is radially inward of the bottom surface of the vertical main groove M2, stress tends to concentrate on the siping bottom, leading to deterioration of durability such as causing crack damage. So the ratio d / (D
1-D2) is in the range of 1.0 or less. In order to further improve the wet running performance, the ratio d / (D1-D2)
Is more preferably 0.6 or more.

Further, in this embodiment, as shown in FIGS.
Similarly, the lateral groove Y2 between the grooves is provided with a shallow bottom portion 25 and a deep bottom portion 26, and the groove bottom 2 of the shallow bottom portion 25 is also provided.
The siping 27 is formed on 5S.

In this example, the lateral groove Y2 connects the main portion 25A of the shallow bottom portion 25 and the main portions 26A and 26A of the deep bottom portions 26 extending from the vertical main grooves M1 and M2 via the connecting portions 29 and 29. The main portions 25A and 26A each have a substantially constant groove depth and extend substantially parallel to the tread surface. The groove depth D2a of the shallow bottom portion 25 is the deepest of the vertical main grooves M1 and M2 forming the rib area 11A.
It is not less than 0.2 times and not more than 0.6 times a, and the groove depth D3a of the deep bottom portion 26 is not less than 0.6 times and not more than 1.0 times the groove depth D1a. The connection part 29
Is divided into upper and lower portions 29A and 29B at a depth of 0.6 × D1a from the tread surface.
The shallow bottom portion 25 is formed by A and the main portion 25, and the deep bottom portion 2 is formed by the lower portion 29B and the main portion 26A.
6 is formed. In addition, the groove length L2a in the tire axial direction at the groove bottom 25S of the shallow bottom portion 25 is 0.2 times or more and 0.7 times the groove length L1a in the tire axial direction at the groove bottom of the lateral groove Y2.
It is less than double.

Further, in this example, the siping 27 is formed substantially in the center of the groove bottom 25S of the shallow bottom portion 25 along the groove center,
Both ends thereof terminate in the shallow portion 25. Note the length L3a of the sipes 27 is 0.5 times or less of the groove length L2a
The depth da of the siping 27 is 0.3 times or more of the difference D2a-D1a of the groove depths.
It is set to 0 times or less. These D1a, D2a, D3
The reason for setting a, L1a, L2a, L3a, and da is the same as that for the lateral groove Y1.

Further, the sipings 20 and 27 have an outer region K which is separated from the tread ground contact edge E by ⅓ of a ground contact width W which is a distance between the tread ground contact edges E and E in the outer area K inward in the tire axial direction. It is effective to provide the above-mentioned ground contact, and when part or all of the sipings 20 and 27 extend further inward of the outer region K in the tire axial direction, cornering power becomes insufficient and steering stability is improved. It is not preferable because it decreases.

In the present application, as shown in FIG. 9a, the siping 27 can be excluded from the lateral groove Y2 between the grooves, and as shown in FIG. 9b, the shallow groove portion 25 is excluded from the lateral groove Y2 so as to have a constant depth. The groove may be used, or the lateral groove Y2 itself may be excluded to form the rib area 11A with the same rib body as the rib area 11B.

The lateral groove Y1 on the shoulder side is shown in FIG.
As shown in a, a shallow bottom portion 15 can be provided between the deep bottom portions 16 on both sides, and as shown in FIG. 10b, the shallow bottom portion 15 is provided outside the deep bottom portion 16 extending from the vertical main groove M2. Alternatively, the shallow bottom portion 15 does not have to have a main portion 15A having a substantially constant depth as shown in FIG. 10c, but has, for example, a polygonal shape such as a substantially triangular cross section, or a substantially arc shape including a da circle. It may be raised.

(Specific example) A tire having a tire size of 205 / 60R15 having the structure shown in FIG. 2 was prototyped according to the specifications of Table 1, and wet running performance, pattern noise performance, and dry steering of the prototype tire during turning. The performance was measured respectively, and the results are shown in the same table in comparison with the tire of the comparative example. As shown in FIG. 11a, the lateral groove Y1 of the comparative example product 1 has the same shape as the lateral groove Y1 shown in FIG.
0 is excluded, and the lateral groove Y1 of the comparative example product 2 is
As shown in FIG. 11b, the siping 20 and the shallow bottom portion 15 are excluded from the lateral groove Y1 of FIG. Each performance test conforms to the test specifications shown in FIGS.

[0048]

[Table 1]

[0049]

Since the present invention is constructed as described above, it is possible to reduce pattern noise while maintaining wet running performance.

[Brief description of drawings]

FIG. 1 is a development view of a tread pattern showing an embodiment of the present invention.

FIG. 2 is a meridional sectional view of a tire showing an embodiment of the present invention.

FIG. 3 is an enlarged sectional view showing a lateral groove on the shoulder side.

FIG. 4 is a diagram showing a relationship between a ratio D2 / D1 and wet running performance and pattern noise performance.

FIG. 5 is a diagram showing a relationship between a ratio L2 / L1 and dry steering performance and pattern noise performance.

FIG. 6 is a diagram showing a relationship between a ratio L3 / L2 and wet running performance, pattern noise performance, and dry steering performance.

FIG. 7 is a diagram showing a relationship between a ratio d / (D1-D2) and wet running performance and pattern noise performance.

FIG. 8 is an enlarged cross-sectional view showing a lateral groove between grooves.

FIG. 9 is a cross-sectional view showing another embodiment of a lateral groove between grooves a and b.

FIG. 10 is a sectional view showing another embodiment of lateral grooves on the shoulder side for all of a, b, and c.

FIG. 11 is a cross-sectional view showing lateral grooves of tires of Comparative Examples 1 and 2 shown in Table 1 for both a and b.

FIG. 12 is a diagram illustrating a conventional technique.

[Explanation of symbols]

2 tread section 10, 11, 11A, 11B rib area 15 Shallow part 16 Deep part 15S, 16S groove bottom 20 siping M, M1, M2 Vertical main groove Y, Y1, Y2 lateral groove

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-104112 (JP, A) JP-A-5-178031 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60C 11/04 B60C 11/12

Claims (3)

(57) [Claims] 1. A tire circumferentially extending on a tread portion.
By providing more than one vertical main groove, the rib area on the shoulder side which forms the tread portion between the outermost vertical main groove in the tire axial direction and the tread contact edge, and the rib area between the grooves formed between the vertical main grooves. In addition, at least in the rib area on the shoulder side, lateral grooves that divide each rib area and form blocks arranged in the circumferential direction are provided, and the lateral groove is a vertical main groove that forms a rib area into which the lateral groove is divided. And a shallow bottom portion having a depth D2 of 0.2 times or more and 0.6 times or less of the groove depth D1 and a depth of more than 0.6 times and 1.0 times or less of the groove depth D1 of the vertical main groove. The groove length L2 in the tire axial direction at the groove bottom of the shallow bottom portion is 0.2 of the groove length L1 in the tire axial direction at the groove bottom of the lateral groove. It is more than twice and less than 1.0 times, and the groove bottom of this shallow bottom part is A pneumatic tire provided with siping having a length L3 in the tire axial direction which is 0.5 times or more and 0.8 times or less the groove length L2. 2. The depth d from the groove bottom of the shallow bottom portion of the siping is 0, which is the difference (D1-D2) between the groove depth D1 of the vertical main groove and the groove depth D2 of the shallow bottom portion. 3 times or more and 1.0
The pneumatic tire according to claim 1, wherein the pneumatic tire is set to be twice or less. 3. The shallow bottom portion is characterized in that one end of the shallow bottom portion extends from the vertical main groove as a starting point.
Pneumatic tire described.