JP7276574B2 - tire - Google Patents

Description

The present invention relates to tires having shoulder main grooves.

Patent Literature 1 below proposes a tire in which shoulder main grooves are arranged closest to the tread end of the tread portion. In general, shoulder main grooves are formed with a large width in order to obtain sufficient drainage, but this tends to cause stone trapping in which foreign objects such as pebbles on the road surface enter while the vehicle is running. If the tire continues to run while the stone is stuck, the bottom surface of the groove may be damaged at the stone stuck portion.

A tire having a shoulder main groove has, for example, a shoulder land portion formed on the outside of the shoulder main groove in the tire axial direction. When this shoulder land portion runs over a step on the road surface such as a curb, a large strain acts on the groove bottom surface of the shoulder main groove. In particular, in a heavy-duty tire that supports a large load, the strain tends to cause damage such as cracks on the bottom surface of the shoulder main groove.

The damage at the bottom of the groove tends to grow gradually as the running distance increases, leading to partial tear damage (tear) in the shoulder land portion. In particular, when the shoulder land portion is formed of ribs continuous in the tire circumferential direction, the above tendency is remarkable.

Japanese Patent Application Laid-Open No. 2017-043208

SUMMARY OF THE INVENTION The present invention has been devised in view of the actual situation as described above, and its main object is to provide a tire capable of suppressing tearing damage to the shoulder land portion.

The present invention provides a tire in which a plurality of main grooves extending continuously in the tire circumferential direction are arranged in a tread portion, the main grooves including a shoulder main groove arranged closest to the tread edge, The groove has a plurality of protuberances in the tire circumferential direction that protrude from the deepest groove bottom surface, and the length of the protuberances in the tire circumferential direction increases toward the tire radial direction inner side.

In the tire of the present invention, in a cross section along the tire circumferential direction, the raised portion includes at least one side surface extending from the groove bottom surface at an angle with respect to the tire radial direction, and continuous with the side surface along the tire circumferential direction. It is desirable to have an extending outer surface.

In the tire of the present invention, it is preferable that the raised portion includes a trapezoidal portion in a cross section along the tire circumferential direction.

In the tire of the present invention, it is preferable that the length of the raised portion in the tire circumferential direction at the bottom surface of the groove is 1.40 to 2.00 times the length of the outer surface in the tire circumferential direction.

In the tire of the present invention, the length of the outer surface in the tire circumferential direction is preferably 0.30 to 0.80 times the length of one pitch of the plurality of raised portions in the tire circumferential direction.

In the tire of the present invention, the height of the raised portion in the tire radial direction is preferably 0.40 to 0.80 times the depth from the edge of the shoulder main groove to the bottom surface of the groove.

In the tire of the present invention, it is preferable that the axial width of the raised portion is 0.30 to 0.60 times the groove width of the shoulder main groove.

In the tire of the present invention, the tread portion has a middle land portion adjacent to the inner side of the shoulder main groove, and the middle land portion is provided with a plurality of middle sipes that are continuous with the shoulder main groove. In each of the middle sipes, it is preferable that a region extending in the tire axial direction from the end on the side of the shoulder main groove passes through a gap between the raised portions adjacent in the tire circumferential direction.

In the tire of the present invention, the depth of the middle sipe is preferably 0.30 to 0.80 times the depth from the edge of the shoulder main groove to the bottom surface of the groove.

In the tire of the present invention, it is preferable that shoulder land portions formed of ribs continuously extending in the tire circumferential direction are formed outside the shoulder main grooves.

In the present invention, the shoulder main groove is provided with a plurality of protuberances in the tire circumferential direction that protrude from the groove bottom surface having the greatest depth. The raised portion can suppress stone trapping. Further, the raised portion locally increases the rubber volume on the bottom surface of the groove, thereby improving the rigidity or durability of the bottom surface of the shoulder main groove.

Since the protuberance has a length in the tire circumferential direction that increases inward in the tire radial direction, the protuberance has high rigidity at its root portion. Therefore, for example, even if the axially outer shoulder land portion of the shoulder main groove rides on a step on the road surface and is greatly deformed, the raised portion can reduce strain at the groove bottom surface of the shoulder main groove. In addition, in the situation described above, the raised portion itself comes into contact with the step, thereby reducing the excessive load acting on the shoulder land portion and effectively suppressing tearing of the shoulder land portion.

1 is a developed view of a tread portion of a tire according to one embodiment of the present invention; FIG. FIG. 2 is an enlarged view of the shoulder main groove, the crown main groove, and the middle land portion of FIG. 1; FIG. 4 is an enlarged perspective view showing a raised portion of the shoulder main groove; 2. (a) is a cross-sectional view taken along the line AA of FIG. 2, and (b) is a cross-sectional view taken along the line BB of FIG. FIG. 3 is a cross-sectional view taken along line CC of FIG. 2;

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a developed view of a tread portion 2 of a tire 1 of this embodiment. The tire 1 of this embodiment is suitably used as, for example, a pneumatic tire for heavy loads. However, the tire of the present invention is not limited to such an aspect.

As shown in FIG. 1, a tread portion 2 of a tire 1 is provided with a plurality of main grooves 3 continuously extending in the tire circumferential direction. The main groove 3 includes a shoulder main groove 4 arranged closest to the tread edge Te, and a crown main groove 5 arranged closer to the tire equator C than the shoulder main groove 4 .

The "tread edge Te" is applied to the tire 1 in a normal state, which is mounted on a normal rim (not shown), filled with a normal internal pressure, and unloaded. This is the outermost grounding position in the axial direction of the tire when grounded.

A "regular rim" is a rim defined for each tire in a standard system that includes standards on which tires are based. For ETRTO, it is "Measuring Rim".

"Regular internal pressure" is the air pressure specified for each tire by each standard in the standard system including the standards on which tires are based. Maximum value described in VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

"Normal load" is the load defined for each tire by each standard in the standard system including the standard on which the tire is based. AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO, it is "LOAD CAPACITY".

In the tread portion 2 of this embodiment, two shoulder main grooves 4 arranged on the tread end Te side and two crown main grooves 5 arranged on both sides of the tire equator C are arranged. Thus, the tread portion 2 is divided into a crown land portion 6 , two middle land portions 7 and two shoulder land portions 8 . The crown land portion 6 is divided between two crown main grooves 5 . The middle land portion 7 is divided between the crown main groove 5 and the shoulder main groove 4 . The shoulder land portion 8 is divided axially outward of the shoulder main groove 4 .

In the shoulder main groove 4, for example, it is desirable that the distance L1 from the tire equator C to the groove centerline is 0.20 to 0.35 times the tread width TW. In the crown main groove 5, for example, it is desirable that the distance L2 from the tire equator C to the groove centerline is 0.05 to 0.10 times the tread width TW. The tread width TW is the axial distance between the tread edges Te of the tire 1 in the normal state.

The shoulder main groove 4 of this embodiment extends linearly, for example. However, it is not limited to such a mode, and the shoulder main groove 4 may, for example, extend in a wavy shape.

In the case of a heavy-duty pneumatic tire, the shoulder main groove 4 preferably has a groove width W1 of, for example, 3.0 to 7.0% of the tread width TW in order to ensure sufficient drainage. From the same point of view, the groove depth of the shoulder main groove 4 is preferably 10 to 25 mm, for example.

FIG. 2 shows an enlarged view of the shoulder main groove 4, the crown main groove 5 and the middle land portion 7 of FIG. FIG. 3 shows a perspective view showing the bottom surface of the shoulder main groove 4. As shown in FIG. As shown in FIGS. 2 and 3, the shoulder main groove 4 has a plurality of protuberances 10 protruding from a groove bottom surface 9 having the greatest depth in the tire circumferential direction. The raised portion 10 can suppress stone trapping. In addition, the raised portion 10 locally increases the rubber volume on the groove bottom surface 9 , thereby improving the rigidity or durability of the groove bottom surface 9 of the shoulder main groove 4 .

As shown in FIG. 3, the protuberant portion 10 of the present invention increases in length in the tire circumferential direction toward the tire radial direction inner side. Therefore, the raised portion 10 has high rigidity at its root portion. Therefore, for example, even if the shoulder land portion 8 on the axially outer side of the shoulder main groove 4 rides on a step on the road surface and is greatly deformed, the protuberance 10 reduces strain on the groove bottom surface 9 of the shoulder main groove 4. can do. In the above-described situation, the raised portion 10 itself comes into contact with the step, thereby reducing the excessive load acting on the shoulder land portion 8 and effectively suppressing tearing of the shoulder land portion 8 . .

FIG. 4(a) shows a cross-sectional view of the raised portion 10 along the tire circumferential direction. FIG. 4(a) corresponds to a cross-sectional view taken along the line AA in FIG. As shown in FIG. 4( a ), the raised portion 10 of the present embodiment has side surfaces 14 on both sides in the tire circumferential direction and an outer surface 15 therebetween in a cross section along the tire circumferential direction. there is

At least one of the side surfaces 14 extends from the groove bottom surface 9 while being inclined with respect to the tire radial direction. In the present embodiment, both side surfaces of the raised portion 10 in the tire circumferential direction extend obliquely with respect to the tire radial direction. However, it is not limited to such an aspect, and the raised portion 10 of the present invention may, for example, have one side surface inclined with respect to the tire radial direction and the other side surface extending along the tire radial direction. good.

The side surface 14 of the present embodiment is, for example, planar. The angle θ1 of the side surface 14 with respect to the tire radial direction is preferably 15 to 30°, for example. Such side surfaces 14 can enhance wet performance and tear resistance performance in a well-balanced manner.

For example, the outer surface 15 continues to the side surfaces 14 on both sides in the tire circumferential direction and extends along the tire circumferential direction. The outer surface 15 of this embodiment is, for example, planar. Thereby, the raised portion 10 includes a trapezoidal portion in a cross section along the tire circumferential direction. Specifically, an area surrounded by a pair of side surfaces 14 and an outer surface 15 of the raised portion 10 and an imaginary line 9a extending from the groove bottom surface 9 has a trapezoidal shape.

The length L3 of the outer surface 15 in the tire circumferential direction is preferably 0.30 times or more, more preferably 0.50 times or more, of the tire circumferential direction pitch length P1 (shown in FIG. 2) of the plurality of raised portions 10. , preferably 0.80 times or less, more preferably 0.70 times or less. Such a raised portion 10 can effectively suppress tearing of the shoulder land portion 8 while suppressing deterioration of the drainage performance of the shoulder main groove 4 . One pitch length P1 of the raised portion 10 corresponds to, for example, the sum of the length L3 of the outer surface 15 in the tire circumferential direction and the length L4 of the gap 16 between adjacent raised portions 10 in the tire circumferential direction.

As shown in FIG. 2, one pitch length P1 of the protuberance 10 is preferably substantially the same as one pitch length of, for example, the plurality of grooves or sipes disposed in the middle land portion 7 . Note that even if there is a difference in the length of one pitch, the phrase "one pitch length is substantially the same" means that the number of protuberances 10 per tire circumference is equal to that of the middle land portion 7 per tire circumference. It shall include a mode that fits within a difference that is equal to the number of grooves or sipes.

One pitch length P1 of the raised portion 10 is preferably larger than, for example, the width W2 of the middle land portion 7 in the axial direction of the tire. In this embodiment, the one-pitch length P1 is preferably 1.15 to 1.30 times the width W2 of the middle land portion 7. As shown in FIG.

As shown in FIG. 4A, the length L5 of the raised portion 10 in the tire circumferential direction at the groove bottom surface 9 is preferably 1.40 times or more, more preferably, the length L3 of the outer surface 15 in the tire circumferential direction. is 1.50 times or more, preferably 2.00 times or less, more preferably 1.90 times or less. Such raised portion 10 exhibits excellent durability at its root portion.

The height h1 from the outer surface 15 of the raised portion 10 to the groove bottom surface 9 is preferably 0.40 times or more, more preferably 0.50 times or more, the depth d1 from the groove edge of the shoulder main groove 4 to the groove bottom surface 9. , preferably 0.80 times or less, more preferably 0.70 times or less. For example, when the shoulder land portion 8 rides on a step, such a raised portion 10 contacts the step and can reduce the distortion of the groove bottom surface 9 of the shoulder main groove 4 .

FIG. 4(b) shows a cross-sectional view of the raised portion 10 along the tire axial direction. FIG. 4(b) corresponds to a cross-sectional view taken along line BB of FIG. As shown in FIG. 4(b), the raised portion 10 preferably has an axial side surface 17 extending radially outward from the groove bottom surface 9, for example. The axial side surface 17 of the present embodiment is, for example, planar. The axial side surface 17 is, for example, slightly inclined from the groove bottom surface 9 outward in the tire radial direction so as to reduce the axial width of the raised portion 10 . The angle of the axial side surface 17 with respect to the tire radial direction is preferably less than 5°, for example. The axial side surface 17 may, for example, extend parallel to the tire radial direction.

In order to improve wet performance and tear resistance performance in a well-balanced manner, the axial width W3 of the raised portion 10 is preferably 0.30 to 0.60 times the groove width W1 of the shoulder main groove 4. . The width W3 is measured at the outer surface 15 of the raised portion 10, for example.

As shown in FIG. 2, the crown main groove 5 extends linearly, for example. The crown main groove 5 preferably has a groove width W4 of 3.0 to 7.0% of the tread width TW, for example. The groove depth of the crown main groove 5 is preferably 10 to 25 mm, for example.

Since the crown main groove 5 is arranged closer to the tire equator C than the shoulder main groove 4, the distortion of the groove bottom surface when running over a step is relatively small. On the other hand, in the present embodiment, since the shoulder main groove 4 is provided with the relatively large raised portion 10, it is desirable that the crown main groove 5 supplements the drainage performance. From this point of view, the crown main groove 5 of the present embodiment preferably has, for example, a plurality of crown protuberances 20 with relatively small rubber volumes.

The crown protruding portion 20 protrudes from the groove bottom surface of the crown main groove 5, and has, for example, a uniform length in the tire circumferential direction from the groove bottom surface to the outer surface. The crown raised portion 20 has, for example, a length in the tire circumferential direction smaller than that of the raised portion 10 arranged in the shoulder main groove 4 . In a more desirable embodiment, the crown ridge 20 has a tire circumferential length that is less than the clearance 16 of the ridge 10 disposed in the shoulder main groove 4 . The crown protuberance 20 suppresses stone trapping in the crown main groove 5, while maintaining the drainage performance of the crown main groove 5 to be greater than that of the shoulder main groove 4, thereby maintaining the wet performance.

The circumferential length L6 of the crown protruding portion 20 is preferably 0.30 to 0.45 times the circumferential length L3 of the outer surface 15 of the protruding portion 10, for example. The crown main groove 5 in which such a crown protuberance 20 is arranged can supplement the drainage performance of the shoulder main groove 4 while exhibiting excellent stone entrapment resistance.

From a similar point of view, it is desirable that the one-pitch length P2 of the crown protruding portion 20 is smaller than, for example, the length L3 of the outer surface 15 of the protruding portion 10 in the tire circumferential direction. In addition, it is desirable that the one-pitch length P2 of the crown protruding portion 20 of the present embodiment is smaller than the length L4 of the gap 16 of the protruding portion 10 in the tire circumferential direction. Specifically, the one-pitch length P2 of the crown protruding portion 20 is 0.45 to 0.55 times the one-pitch length P1 of the protruding portion 10 .

The axial width W5 of the crown protuberance 20 is preferably smaller than the width W3 of the protuberance 10, for example. Specifically, the width W5 of the crown protruding portion 20 is preferably 0.70 to 0.80 times the width W3 of the protruding portion 10. FIG.

FIG. 5 shows a CC cross-sectional view of the crown ridge 20 of FIG. As shown in FIG. 5, the crown ridge 20 preferably has a height that is less than, for example, the height h1 of the ridge 10 (shown in FIG. 4(a)). The height h2 of the crown protuberance 20 is preferably 0.25 to 0.40 times the height h1 of the protuberance 10, for example. Such a crown protuberance 20 can enhance wet performance and stone-biting resistance in a well-balanced manner.

As shown in FIG. 2, the middle land portion 7 has a plurality of middle recesses 21 on the side wall surface in the axial direction of the tire. The middle recessed portion 21 is recessed toward the center of the middle land portion 7 in the axial direction of the tire.

In the tread plan view, it is desirable that each of the middle recesses 21 on the side of the shoulder main groove 4 has a region extending in the axial direction of the tire, for example, passing through the gap 16 between the protuberances 10 adjacent to each other in the tire circumferential direction. Such arrangement of the middle recessed portion 21 helps to improve wet performance.

The middle land portion 7 is provided with, for example, a plurality of middle shallow grooves 22 and a plurality of middle sipes 23 . In this specification, a "sipe" is a cut with a width of less than 1.5 mm.

The middle shallow groove 22 continues with the shoulder main groove 4, for example. The middle shallow groove 22 of this embodiment extends from the shoulder main groove 4 to the crown main groove 5 and completely crosses the middle land portion 7 . Also, the middle shallow groove 22 has, for example, an intermediate portion 22a and end portions 22b on both sides thereof. The intermediate portion 22a is inclined with respect to the tire axial direction. The end portions 22b are connected to both sides of the intermediate portion 22a, are inclined with respect to the tire axial direction at an angle smaller than that of the intermediate portion 22a, and communicate with the shoulder main groove 4 or the crown main groove 5. As shown in FIG.

The middle shallow groove 22 continues to the shoulder main groove 4 at a position other than the middle recessed portion 21, for example. In this embodiment, when the middle land portion 7 touches the ground, the middle shallow groove 22 tends to open and stone trapping occurs near the end of the middle shallow groove 22 . Therefore, in the tread plan view, it is desirable that the region where the end of the middle shallow groove 22 extends axially outward intersects the raised portion 10 . This effectively suppresses the stone trapping.

The middle shallow groove 22 has a groove width larger than that of the middle sipe 23, for example. A groove width W6 of the middle shallow groove 22 is preferably less than 3.0 mm, for example.

The bottom of the middle shallow groove 22 is desirably positioned radially outward of the outer surface 15 of the raised portion 10 . Specifically, the depth of the middle shallow groove 22 is preferably 0.10 to 0.30 times the depth of the shoulder main groove 4, for example. Such a shallow middle groove 22 can maintain the rigidity of the middle land portion 7 high, and is useful for enhancing steering stability.

The middle sipe 23 continues with the shoulder main groove 4, for example. The middle sipe 23 of this embodiment extends from the shoulder main groove 4 to the crown main groove 5 and completely crosses the middle land portion 7 . Moreover, the middle sipe 23 includes, for example, an intermediate sipe portion 23a and an end sipe portion 23b. The intermediate sipe portion 23a is inclined, for example, in the opposite direction to the intermediate portion 22a of the middle shallow groove 22 with respect to the axial direction of the tire, and intersects the intermediate portion 22a. The end sipe portions 23b are inclined, for example, in the opposite direction to the intermediate sipe portions 23a with respect to the axial direction of the tire, and continue to both sides of the intermediate sipe portions 23a. The end sipe portion 23b is desirably connected to the middle recessed portion 21, for example.

In general, even if ground pressure acts on the land portion and the sipe walls come into contact with each other, a slight space remains in the sipe, so that the sipe can exhibit water absorbency and contribute to the improvement of wet performance. However, when the middle sipe 23 is adjacent to the raised portion 10, the water absorbed by the middle sipe 23 is less likely to move toward the shoulder main groove 4 during wet running, and the water absorption of the middle sipe 23 may be hindered. be. For this reason, in the present embodiment, each of the plurality of middle sipes 23 has an axially extending region of the end on the side of the shoulder main groove 4 that passes through the gap 16 of the adjacent raised portions 10 in the tire circumferential direction. desirable. As a result, the water absorbency of the middle sipe 23 is maintained, and excellent wet performance is obtained.

The depth of the middle sipe is preferably 0.30 times or more, more preferably 0.40 times or more, of the depth d1 (shown in FIG. 4(a)) from the groove edge of the shoulder main groove 4 to the groove bottom surface 9. , preferably 0.80 times or less, more preferably 0.70 times or less. In a more preferred embodiment, the bottom of the middle sipe 23 is preferably radially inward of the outer surface 15 of the raised portion 10 provided in the shoulder main groove 4 . Such a middle sipe 23 has high water absorbency and can improve wet performance.

As shown in FIG. 1, the shoulder land portion 8 formed on the outer side of the shoulder main groove 4 is desirably configured as, for example, a rib continuously extending in the tire circumferential direction. Grooves and sipes are not arranged in the shoulder land portion 8 of the present embodiment. Such a shoulder land portion 8 has high rigidity, but tends to cause a large strain on the bottom surface 9 of the shoulder main groove 4 when it runs over a step. In the present embodiment, such a tendency can be effectively alleviated by the raised portion 10 described above.

Although the tire of 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 implemented in various ways.

A heavy-duty pneumatic tire of size 11R22.5 having the basic tread pattern shown in FIG. As Comparative Example 1, a tire in which the shoulder main groove was not provided with the protuberant portion was experimentally produced. As Comparative Example 2, a tire in which the circumferential length of the raised portion was the same from the bottom surface of the groove to the outer surface was produced. Each test tire was constructed with a substantially identical tread pattern, except for ridge specifications. Each test tire was tested for tear resistance and wet performance. Common specifications and test methods for each test tire are as follows.
Mounting rim: 22.5 x 8.25
Tire pressure: 720kPa
Test vehicle: 10t truck, 50% of the standard load capacity is loaded in the center of the platform. Test tire mounting position: All wheels

<Tear resistance performance>
A test tire was used after the tire temperature was held at 80° C. for 5 days to facilitate tearing. After the test vehicle equipped with this test tire was turned in a steady circle and the tire temperature was set to 60°C, it entered a curb with a height of 10 cm at an angle of 10° with respect to its length direction and ran over it multiple times. We measured the number of curb run-up until a tear occurred on the shoulder land. The results are indexed with the tire of the comparative example being 100, and the larger the numerical value, the better the tear resistance performance.

<Wet Performance>
Under the following conditions, the passing time was measured when the test vehicle passed the test course with a total length of 10m. The results are shown as an index with the passing time of the comparative example set to 100. A smaller value indicates better wet performance.
Road surface: Asphalt with a water film of 5 mm thickness.

As a result of the test, it was confirmed that the tires of Examples exhibited excellent tear resistance performance. In addition, it was confirmed that the tire of the embodiment was suppressed in deterioration of wet performance.

2 Tread Part 3 Main Groove 4 Shoulder Main Groove 9 Groove Bottom 10 Raised Part Te Tread Edge

Claims (9)

A tire having a plurality of main grooves extending continuously in the tire circumferential direction in the tread portion,
The main grooves include a shoulder main groove arranged closest to the tread edge and a crown main groove arranged closer to the tire equator than the shoulder main groove,
The shoulder main groove has a plurality of protrusions in the tire circumferential direction that protrude from a groove bottom surface having the greatest depth,
The crown main groove has a plurality of crown protuberances protruding from the groove bottom surface of the crown main groove in the tire circumferential direction,
The length of the protuberance in the tire circumferential direction increases toward the tire radial direction inner side,
The raised portion includes two side surfaces extending in the tire radial direction on both sides in the tire circumferential direction, and an outer surface connecting to the two side surfaces and extending along the tire circumferential direction,
The crown raised portion includes two side surfaces extending in the tire radial direction on both sides in the tire circumferential direction, and an outer surface continuous with the two side surfaces and extending along the tire circumferential direction,
The length of the outer surface of the crown protruding portion in the tire circumferential direction is smaller than the length of the outer surface of the protruding portion in the tire circumferential direction,
the axial width of the outer surface of the crown protuberance is smaller than the axial width of the outer surface of the protuberance;
tire. The tire according to claim 1, wherein the length of the outer surface of the crown protuberance in the tire circumferential direction is 0.30 to 0.45 times the length of the outer surface of the protuberance in the tire circumferential direction. One of said crown ridges corresponding to the sum of the tire circumferential length of said outer surface of one said crown ridge and the tire circumferential length of the gap in said outer surface for two adjacent said crown ridges. 3. A tire according to claim 1 or 2, wherein the pitch length is smaller than the tire circumferential length of the gap in the outer surface for two adjacent ridges. One of said crown ridges corresponding to the sum of the tire circumferential length of said outer surface of one said crown ridge and the tire circumferential length of the gap in said outer surface for two adjacent said crown ridges. The pitch length corresponds to the sum of the tire circumferential length of the outer surface of one of the raised portions and the tire circumferential length of the gap on the outer surface of two adjacent raised portions. The tire according to any one of claims 1 to 3, which is 0.45 to 0.55 times one pitch length of. A tire according to any preceding claim, wherein the height of the crown ridge is 0.25 to 0.40 times the height of the ridge. 6. The tire according to any one of claims 1 to 5, wherein a shoulder land portion comprising a rib extending continuously in the tire circumferential direction is formed outside the shoulder main groove. 7. The length in the tire circumferential direction of the outer surface of the crown protruding portion is smaller than the length in the tire circumferential direction of the gap in the outer surface between two protruding portions adjacent in the tire circumferential direction. or the tire according to item 1. One of said crown ridges corresponding to the sum of the tire circumferential length of said outer surface of one said crown ridge and the tire circumferential length of the gap in said outer surface for two adjacent said crown ridges. 8. A tire according to any one of the preceding claims, wherein the pitch length is less than the tire circumferential length of the outer surface of the ridge. 9. The method according to any one of claims 1 to 8, wherein the axial width of the outer surface of the crown protruding portion is 0.70 to 0.80 times the axial width of the outer surface of the protruding portion. Tires as stated.

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