Heavy-duty pneumatic tires

Abstract

To provide a pneumatic tire for suppressing a deterioration in heating durability while maintaining a wear suppression effect of a shoulder land part.SOLUTION: In a pneumatic tire for a heavy load, a tread part includes a pair of shoulder land parts 20. At least one of the pair of shoulder land parts 20 is divided into an inner main part 21 in a tire axial direction and a sacrifice rib 22 outside the tire axial direction of the main part 21 by providing a narrow groove 12 continuing in a tire circumferential direction. In the sacrifice rib 22, a ratio (Wr / Ws) of a width Wr in the tire axial direction of a root part in a tire radial direction to a width Ws in the tire axial direction on outside surface in the tire radial direction is 1.0 or more. A minimum distance Lw between a maximum thickness Ls of defining a maximum thickness Wmax of the shoulder land part 20 measured in a normal direction to a tire inner cavity surface 30 and the narrow groove 12 is 5.0 mm or less on the side of at least one shoulder land 20 side.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Conventionally, heavy-duty pneumatic tires have been proposed that have sacrificial ribs separated by narrow grooves in the shoulder land portions of the tread (see, for example, Patent Document 1 below). These sacrificial ribs concentrate wear on themselves, thereby preventing wear from spreading to the entire shoulder land portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-36817 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to maintain the wear suppression effect of the shoulder land portion for a long period of time, it is necessary to ensure the rigidity of the sacrificial rib itself and prevent damage during driving. From this perspective, it is desirable to give the sacrificial rib a reasonable width or rubber volume.

[0005] On the other hand, the shoulder land portions of heavy-duty pneumatic tires have a large rubber volume and are subject to large deformation during running under load, which makes them prone to heat generation during running. Therefore, increasing the size of the sacrificial rib leads to further increase in heat generation in the shoulder land portions during running, which in turn leads to a problem of worsening the heat generation durability of the tire.

[0006] The present invention was devised in consideration of the above-mentioned problems, and its main object is to provide a heavy-duty pneumatic tire that can improve heat resistance while maintaining the effect of suppressing wear in the shoulder land portion. [Means for solving the problem]

[0007] The present invention is a heavy-duty pneumatic tire having a tread portion, the tread portion including a pair of shoulder circumferential grooves that are continuous in the tire circumferential direction, and a pair of shoulder land portions that are sectioned axially outward of the pair of shoulder circumferential grooves, at least one of the pair of shoulder land portions having a narrow groove that is continuous in the tire circumferential direction, thereby dividing the sacrificial rib into a main portion on the axially inner side of the tire and a sacrificial rib on the axially outer side of the main portion, the ratio (Wr / Ws) of the axial width Wr of the sacrificial rib at a root portion in the tire radial direction to the axial width Ws of the sacrificial rib at an outer surface in the tire radial direction is 1.0 or more, and the shortest distance Lw between the narrow groove and a maximum thickness line that defines the maximum thickness of the shoulder land portion measured in the normal direction to the tire cavity surface is 5.0 mm or less on the side of at least one of the shoulder land portions.

[0008] In another aspect of the present invention, the shortest distance Lw may be set to 1.0 mm or less.

[0009] In another aspect of the invention, the maximum thickness line may intersect the narrow groove.

[0010] In another aspect of the present invention, the ratio (Wr / Ws) may be in the range of 1.5 to 2.5.

[0011] In another aspect of the present invention, the outer surface of the sacrificial rib may be located radially inward of the tire so as to form a step in the tire radial direction relative to an outer surface of the main portion in the tire radial direction.

[0012] In another aspect of the present invention, the step may be 2.0 to 3.0 mm.

[0013] In another aspect of the present invention, the narrow groove includes a groove bottom which is the deepest position, and in a cross section of the narrow groove, the narrow groove includes an inner groove wall and an outer groove wall in the tire axial direction, the inner groove wall includes an inner recessed portion recessed axially inward on the groove bottom side, and the outer groove wall includes an outer recessed portion recessed axially outward on the groove bottom side.

[0014] In another aspect of the present invention, the height H1 (mm) from the groove bottom to the radially outer end of the inner recess may be less than the height H2 (mm) from the groove bottom to the radially outer end of the outer recess.

[0015] In another aspect of the present invention, the height H1 (mm) from the groove bottom to the radially outer end of the inner recess may be lower than the height H2 (mm) from the groove bottom to the radially outer end of the outer recess.

[0016] In another aspect of the present invention, when the groove depth of the narrow groove is D (mm), the following formula (1) can be satisfied. 3.0mm≦H1≦H2≦0.50×D …(1)

[0017] In another aspect of the invention, the maximum thickness line may intersect the inner recess or the outer recess of the striation. [Effects of the Invention]

[0018] By adopting the above-described configuration, the heavy-duty pneumatic tire of the present invention can improve heat resistance while maintaining the effect of suppressing wear of the shoulder land portion. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view of a heavy-duty pneumatic tire showing one embodiment of the present invention. [Figure 2] FIG. 2 is a partial enlarged view of the shoulder land portion of FIG. [Figure 3] FIG. 2 is a partial enlarged view of the shoulder land portion of FIG. [Figure 4]FIG. 10 is a partially enlarged view of a shoulder land portion showing another embodiment. [Figure 5] FIG. 10 is a partial cross-sectional view of a shoulder land portion showing another embodiment. [Figure 6] FIG. 10 is a partial cross-sectional view of a shoulder land portion showing another embodiment. [Figure 7] FIG. 10 is a partial cross-sectional view of a shoulder land portion showing another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of the present invention will now be described with reference to the drawings. It should be noted that throughout the embodiments herein, identical or common elements are designated by the same reference numerals and detailed descriptions thereof will not be repeated.

[0021] Fig. 1 is a cross-sectional view of a heavy-duty pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 of this embodiment, and Fig. 2 is a partially enlarged view of its shoulder land portion 20. In Fig. 1, the tire 1 is in a normal state.

[0022] In this specification, the normal state means a state in which the tire is mounted on a normal rim (not shown), inflated to the normal internal pressure, and no load is applied. Unless otherwise specified, the dimensions of each part of the tire 1 refer to values ​​in the normal state.

[0023] In this specification, a "genuine rim" is a rim that is defined for each tire in a standard system that includes the standard on which the tire is based, such as a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO.

[0024] In this specification, the term "normal internal pressure" refers to the air pressure determined for each tire by a standard system including the standard on which the tire is based, such as "maximum air pressure" in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, or "INFLATION PRESSURE" in the case of ETRTO.

[0025] 1, the tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4 each having a bead core 5 embedded therein. The tire 1 of this embodiment is configured as a pneumatic tire in which an air-impermeable inner liner rubber is arranged on the tire cavity surface 30.

[0026] The tire 1 also includes a carcass 6 extending across the pair of bead cores 5, 5, and a belt layer 7 disposed on the outer side of the carcass 6 in the tire radial direction.

[0027] The carcass 6 of this embodiment includes, for example, at least one carcass ply 6A in which a plurality of steel cords are covered with a topping rubber. The carcass cords have a radial structure oriented at an angle of, for example, 80 to 90 degrees with respect to the tire equator C.

[0028] The carcass ply 6A includes, for example, a main body portion 6a extending between the pair of bead cores 5 and a pair of turned-up portions 6b folded back from the inside to the outside in the axial direction of the tire around the pair of bead cores 5. In a preferred embodiment, each bead portion 4 has a bead apex 8 made of hard rubber that extends tapered from the bead core 5 to the outside in the radial direction of the tire between the main body portion 6a and the turned-up portions 6b of the carcass ply 6A.

[0029] The belt layer 7 is composed of a plurality of belt plies (four in this embodiment). Each belt ply includes steel cords oriented at an angle of, for example, 10 to 60 degrees with respect to the tire equator C. Such a belt layer 7 hoops the carcass 6 and increases the rigidity of the tread portion 2.

[0030] A plurality of circumferential grooves extending continuously in the tire circumferential direction are formed in the tread portion 2. The circumferential grooves in this embodiment include a pair of shoulder circumferential grooves 9 and one or more crown circumferential grooves 10 arranged between them. Each of the circumferential grooves 9 and 10 has a groove width large enough to prevent the groove from closing when the tire 1 comes into contact with the ground under a normal load. Note that the "normal load" refers to the load determined for each tire by each standard in the standard system including the standard on which the tire 1 is based, and is the maximum load capacity in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "LOAD CAPACITY" in the case of ETRTO.

[0031] The groove width of each of the circumferential grooves 9 and 10 is not particularly limited, but is, for example, 5 mm or more, preferably 6 mm or more, and is, for example, 15 mm or less. The groove depth of each of the circumferential grooves 9 and 10 is, for example, 8 mm or more, preferably 10 mm or more, and is, for example, 18 mm or less.

[0032] A pair of shoulder land portions 20 are defined in the tread portion 2, axially outward of the pair of shoulder circumferential grooves 9. Each of the pair of shoulder land portions 20 includes a tread contact edge Te, and constitutes the outermost land portion in the tread portion 2. In this specification, the term "tread contact edge" refers to the axially outermost position on the contact patch when the tire 1 in a normal state is placed in contact with the ground flat with a normal load and a camber angle of 0 degrees.

[0033] A fine groove 12 extending continuously in the tire circumferential direction is formed in at least one of the pair of shoulder land portions 20. In this embodiment, as a preferred aspect, the fine groove 12 is formed in both of the pair of shoulder land portions 20.

[0034] The narrow grooves 12 are arranged in the shoulder land portion 20 closer to the tread ground contact edge Te than the shoulder circumferential grooves 9. This divides the shoulder land portion 20 into a main portion 21 on the axially inner side of the tire and a sacrificial rib 22 on the axially outer side of the tire.

[0035] 2, the sacrificial rib 22 includes the tread ground contact edge Te and constitutes the end of the shoulder land portion 20. Furthermore, the sacrificial rib 22 has a smaller width in the tire axial direction than the main portion 21, and therefore has lower rigidity than the main portion 21. Such sacrificial ribs 22 move appropriately when the tire is running, concentrating wear on themselves, thereby preventing uneven wear from spreading to the main portion 21.

[0036] The narrow groove 12 desirably has a groove width Gw such that a pair of groove walls come into contact when the tire 1 is in contact with the ground under a normal load. This allows the sacrificial rib 22 to come into contact with the main portion 21 while ensuring deformation of the sacrificial rib 22 during tire running. This reduces the wear energy acting on the main portion 21, suppressing uneven wear there. From this perspective, the groove width Gw of the narrow groove 12 is not particularly limited, but is desirably in the range of 0.3 to 6.0 mm, for example. Similarly, the groove depth D of the narrow groove 12 is desirably in the range of 10 to 18 mm, for example. Note that the narrow groove 12 of this embodiment has a substantially constant groove width Gw.

[0037] If the rigidity of the sacrificial rib 22 is reduced, damage such as chipping or cracking may occur in the sacrificial rib 22 even if the tire has sufficient remaining wear life. Therefore, to maintain the wear-suppressing effect of the shoulder land portion 20 over a long period of time, it is necessary to ensure the rigidity of the sacrificial rib 22 itself. In response to this issue, as shown in FIG. 2 , the sacrificial rib 22 of this embodiment has a ratio (Wr / Ws) of the tire axial width Wr at the tire radial root portion 22a to the tire axial width Ws at the tire radial outer surface 22b, which is 1.0 or greater. This increases the rigidity of the root portion 22a of the sacrificial rib 22, thereby making it possible to suppress unintended early damage to the sacrificial rib 22. This helps maintain the wear-suppressing effect of the shoulder land portion 20 over a long period of time.

[0038] In this specification, as shown in Fig. 2, the root portion 22a of the sacrificial rib 22 is defined by an axial line extending axially outward from the groove bottom 12a, which is the deepest position of the narrow groove 12. The width Wr of the root portion 22a of the sacrificial rib 22 is the axial distance from the groove bottom 12a of the narrow groove 12 to the outer surface of the tire 1. However, when the groove bottom 12a of the narrow groove 12 is continuous in the axial direction, the groove bottom 12a is specified as the axially outermost position of the groove bottom 12a. The axial width Ws of the sacrificial rib 22 at the outer surface 22b is specified as the axial distance from the axially outer groove edge of the narrow groove 12 to the tread contact edge Te.

[0039] In order to further enhance the above-mentioned effect of the sacrificial rib 22, it is desirable that the width of the sacrificial rib 22 in the tire axial direction gradually decrease from the root portion 22a toward the outer surface 22b.

[0040] In particular, the ratio (Wr / Ws) is preferably greater than 1.0, more preferably 1.5 or more, and even more preferably 2.0 or more.

[0041] On the other hand, if the ratio (Wr / Ws) is too large, the rigidity of the sacrificial rib 22 is improved, but there is a risk that the effect of suppressing uneven wear during tire running due to the inherent flexible deformation of the sacrificial rib 22 will not be obtained. From this perspective, it is desirable that the ratio (Wr / Ws) be, for example, 2.5 or less.

[0042] Although not particularly limited, it is desirable that the width Ws of the outer surface 22b of the sacrificial rib 22 in the tire axial direction be in the range of, for example, 5 to 15 mm.

[0043] Fig. 3 shows a partially enlarged view of the shoulder land portion 20 provided with the narrow groove 12. As shown in Fig. 3, in the tire 1 of this embodiment, the shortest distance Lw between the narrow groove 12 and the maximum thickness line Ls, which defines the maximum thickness Wmax of the shoulder land portion 20 measured in the normal direction to the tire cavity surface 30, is 5.0 mm or less. In this embodiment, the maximum thickness line Ls is a straight line that passes through the tread ground contact edge Te and is perpendicular to the tire cavity surface 30.

[0044] In a heavy-duty pneumatic tire 1, the shoulder land portions 20 have a large rubber volume and are subject to significant deformation during tire load running, making them prone to heat generation. The heat stored in the shoulder land portions 20 affects the carcass 6 and belt layer 7, causing looseness, separation, and the like. In the present invention, as described above, by arranging the portion of the shoulder land portion 20 with the maximum thickness Wmax close to the narrow groove 12 at a certain distance, heat generated in the shoulder land portions 20 during running can be effectively dissipated to the outside of the tire through the narrow groove 12. Therefore, the tire 1 of this embodiment can improve heat resistance.

[0045] If the shortest distance Lw exceeds 5.0 mm, the heat in the shoulder land portion 20 is difficult to dissipate through the narrow groove 12, and as a result, deterioration of heat resistance cannot be effectively prevented.

[0046] In a preferred embodiment, the shortest distance Lw is set to 1.0 mm or less, which brings the part of the shoulder land portion 20 with the maximum thickness Wmax closer to the narrow groove 12, thereby further improving the heat dissipation effect of the shoulder land portion 20 while the tire is running.

[0047] In a more preferred embodiment, as shown in Fig. 4, it is desirable that the maximum thickness line Ls of the shoulder land portion 20 intersects with the narrow groove 12. This further improves the heat dissipation effect of the shoulder land portion 20 while the tire is running.

[0048] As shown in FIG. 2 , the outer surface 22b of the sacrificial rib 22 in the tire radial direction is desirably positioned radially inward relative to the outer surface 21b of the main portion 21 in the tire radial direction so as to form a step S in the tire radial direction. In this configuration, the height of the sacrificial rib 22 in the tire radial direction is reduced, thereby improving the bending rigidity and other properties of the sacrificial rib 22. This improves the crack resistance and tear resistance of the sacrificial rib 22. In particular, in this configuration, the bending rigidity of the sacrificial rib 22 in the tire axial direction is improved, so that the sacrificial rib 22 comes into contact with the main portion 21 and supports the main portion 21 during tire travel, thereby reducing the wear energy acting on the main portion 21. This helps to further suppress uneven wear of the main portion 21 of the shoulder land portion 20.

[0049] To further enhance the above-mentioned effect, it is desirable that the step S be 2.0 mm or more in terms of distance in the tire radial direction. On the other hand, if the step S is excessively large, it becomes difficult for the sacrificial rib 22 to contact the ground when the tire is running, and therefore the main portion 21 cannot be supported when running straight or cornering, which may reduce the effect of so-called sacrificial wear. From this perspective, it is desirable that the step S be 3.0 mm or less, for example.

[0050] 5 and 6 are partial cross-sectional views of the shoulder land portion 20 showing another embodiment of the present invention. This embodiment is basically the same as the previous embodiment except for the shape of the fine grooves 12. Specifically, as shown in FIG. 5, the fine grooves 12 differ from the previous embodiment in that they have a portion where the groove width is enlarged on the groove bottom 12a side in cross section.

[0051] More specifically, the narrow groove 12 includes an inner groove wall 12i and an outer groove wall 12o in the tire axial direction, the inner groove wall 12i includes an inner recess 13i recessed axially inward on the groove bottom 12a side, and the outer groove wall 12o includes an outer recess 13o recessed axially outward on the groove bottom 12a side. In this embodiment, the inner recess 13i and the outer recess 13o are both formed as arc-shaped concave curved surfaces, and are smoothly connected to each other at the groove bottom 12a.

[0052] Such narrow grooves 12 have an increased groove surface area, which allows the heat stored in the shoulder land portions 20 to be more effectively dissipated to the outside of the tire, thereby further improving the heat resistance of the tire 1. In addition, strain acting on the narrow grooves 12 during tire running is widely dispersed in the inner recessed portion 13i and the outer recessed portion 13o, and concentration at the groove bottom 12a is suppressed. Therefore, in this embodiment, the crack resistance at the groove bottom 12a can be further improved.

[0053] In the narrow groove 12 of this embodiment, the groove width Gw is formed relatively small in the portion radially outward of the inner recess 13i and the outer recess 13o, which suppresses excessive deformation of the sacrificial rib 22 during tire running, and suppresses the spread of uneven wear of the main portion 21 as before.

[0054] In a preferred embodiment, the height H1 (mm) from the groove bottom 12a to the outer end of the inner recess 13i in the tire radial direction is desirably not more than the height H2 (mm) from the groove bottom 12a to the outer end of the outer recess 13o in the tire radial direction. With such a configuration, the strain near the groove bottom 12a of the narrow groove 12 under load is alleviated, and thus, damage to the sacrificial rib 22 due to crack generation at the groove bottom 12a of the narrow groove 12 can be suppressed over a long period.

[0055] In a more preferred embodiment, it is desirable that the heights H1 and H2 satisfy the relationship H1 < H2. By forming the outer recess 13o larger than the inner recess 13i in the tire radial direction in this way, the flexibility of the root portion 22a of the sacrificial rib 22 is further improved. Therefore, the crack resistance performance at the groove bottom 12a of the narrow groove 12 is further improved, and thus, damage to the sacrificial rib 22 is further suppressed.

[0056] In a particularly preferred embodiment, when the groove depth of the narrow groove 12 is D (mm), it is desirable that the heights H1 and H2 satisfy the following formula (1). 3.0 mm ≤ H1 ≤ H2 ≤ 0.50 × D …(1)

[0057] By satisfying formula (1), the inner recess 13i and the outer recess 13o are formed as concave curved surfaces with a sufficiently large radius of curvature (for example, R ≥ 3.0 mm), and the above effect is further enhanced. Also, by setting both the heights H1 and H2 to be not more than 0.50 × D, a significant decrease in the rigidity of the sacrificial rib 22 can be suppressed.

[0058] Fig. 7 shows an even more preferred embodiment. In this embodiment, the maximum thickness line Ls intersects with the inner recess 13i or the outer recess 13o of the narrow groove 12. In this embodiment, the maximum thickness line Ls intersects with both the inner recess 13i and the outer recess 13o of the narrow groove 12 where a more heat dissipation effect can be expected. According to such an embodiment, the heat stored in the shoulder land portion 20 is more effectively released to the outside of the tire, and thus, the heat generation durability is further improved. [[ID=I19]]

[0059] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above specific disclosure, and can be implemented in various modified forms within the scope of the technical idea described in the claims. [Example]

[0060] More specific, non-limiting examples of the present invention will now be described. Heavy-duty pneumatic tires with the basic structure shown in Figure 1 were prototyped based on the specifications in Table 1, and the uneven wear resistance and heat resistance of the shoulder land area of ​​each tire were tested. The common specifications and test methods for each prototype tire are as follows: Tire size: 295 / 75R22.5 Rim: 22.5 x 8.25 Internal pressure: 830kPa

[0061] [Uneven wear resistance on shoulder land] Each test tire was fitted to all wheels of a 10-ton truck, which was driven 20,000 km on an asphalt test course. Afterwards, the ratio of the amount of wear on the main part of the shoulder land area to the amount of wear on the land area axially inside the tire was calculated. The result was calculated by multiplying the wear ratio by 100, with the number closer to 100 indicating better performance.

[0062] [Heat resistance] A normal load (27.5 kN) was applied to each test tire and it was run on a drum test machine. The speed was increased by 10 km / h every 120 minutes from 40 km / h, and the running time until the tire broke was measured. The results are expressed as an index, with the running time of Comparative Example 1 being set at 100, and a higher value indicates better performance. The test results are shown in Table 1.

[0063] [Table 1]

[0064] As a result of the test, it was confirmed that the tires of the example had improved heat resistance while maintaining the same level of uneven wear resistance performance of the shoulder land portion compared to the tires of the comparative example.

[0065] Next, using Example 1 as the base, the step between the main part and the sacrificial rib and the recessed portion of the narrow groove wall were changed, and the crack and tear resistance of the sacrificial rib and the groove bottom crack resistance of the narrow groove were also tested. The test method was as follows.

[0066] [Crack and tear resistance of sacrificial ribs, crack resistance at the bottom of narrow grooves] A normal load (27.5 kN) was applied to each test tire, and the tire was run on a drum testing machine that replicated an asphalt road surface. The running speed was 40 km / h, and the running time was 145 hours. After the run, the degree of damage to the sacrificial rib, the size of cracks at the bottom of the fine grooves, and the degree of damage caused by heat were quantified. The results are expressed as an index, with Example 1 being 100, and a higher index indicates better performance. The groove depth D of the fine grooves was 15 mm. The test results are shown in Table 2.

[0067] [Table 2]

[0068] It was also confirmed that in configurations where the step between the main part and the sacrificial rib was optimized, or where a recess was provided on the bottom side of the narrow groove, the crack and tear resistance of the sacrificial rib and the groove bottom crack resistance of the narrow groove were significantly improved. [Explanation of symbols]

[0069] 1. Heavy-duty pneumatic tires 2 Tread section 9 Shoulder circumferential groove 12 Narrow groove 12a groove bottom 12i inner groove wall 12o outer groove wall 13i Inner recess 13o outer recess 20 Shoulder Land Section 21 Main Section 21b Outer surface of main part 22 Sacrificial Rib 22a Root of sacrificial rib 22b Outer surface of sacrificial rib Ls Maximum thickness line Lw Shortest distance S step Wmax Maximum thickness of shoulder land

Claims

1. A heavy-duty pneumatic tire having a tread portion, the tread portion includes a pair of shoulder circumferential grooves that are continuous in the tire circumferential direction, and a pair of shoulder land portions that are separated axially outward of the pair of shoulder circumferential grooves, At least one of the pair of shoulder land portions is provided with a narrow groove that is continuous in the tire circumferential direction, thereby dividing the shoulder land portion into a main portion on the axially inner side of the tire and a sacrificial rib on the axially outer side of the main portion, The sacrificial rib has a ratio (Wr / Ws) of a width Wr in the tire axial direction at a root portion in the tire radial direction to a width Ws in the tire axial direction at an outer surface in the tire radial direction of 1.0 or more, The width of the sacrificial rib in the tire axial direction gradually decreases from the root portion to the outer surface, The narrow groove includes a groove bottom which is the deepest position, In a cross section of the narrow groove, the narrow groove includes an inner groove wall and an outer groove wall in the tire axial direction, the inner groove wall includes an inner recess recessed inward in the tire axial direction on the groove bottom side, the outer groove wall includes an outer recess recessed toward the tire axially outer side on the groove bottom side, On the side of the at least one shoulder land portion, a maximum thickness line defining a maximum thickness of the shoulder land portion measured in a normal direction to a tire cavity surface intersects with the inner recessed portion or the outer recessed portion of the narrow groove. Heavy-duty pneumatic tires.

2. A heavy-duty pneumatic tire as described in claim 1, wherein the ratio (Wr / Ws) is in the range of 1.5 to 2.

5.

3. A heavy-duty pneumatic tire as described in claim 1 or 2, wherein the outer surface of the sacrificial rib is located radially inward of the tire relative to the radial outer surface of the main portion so as to form a radial step in the tire.

4. A heavy-duty pneumatic tire as described in claim 3, wherein the step is 2.0 to 3.0 mm.

5. A heavy-duty pneumatic tire as described in any one of claims 1 to 4, wherein the height H1 (mm) from the groove bottom to the radially outer end of the inner recess is less than or equal to the height H2 (mm) from the groove bottom to the radially outer end of the outer recess.

6. A heavy-duty pneumatic tire as described in claim 5, wherein the height H1 (mm) from the groove bottom to the radially outer end of the inner recess is lower than the height H2 (mm) from the groove bottom to the radially outer end of the outer recess.

7. A heavy-duty pneumatic tire as described in claim 5 or 6, which satisfies the following formula (1) when the groove depth of the narrow groove is D (mm). 3.0 mm ≦ H1 ≦ H2 ≦ 0.50 × D ... (1)

8. A heavy-duty pneumatic tire as described in any one of claims 1 to 7, wherein the maximum thickness line intersects with both the inner recess and the outer recess of the narrow groove.

9. The tread portion includes a belt layer having a plurality of belt plies, 9. The heavy-duty pneumatic tire according to claim 1, wherein an outer end of the belt layer in the tire axial direction is located axially inward of the narrow groove and beyond the maximum thickness line in the tire axial direction.

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