A pneumatic tire including a plurality of circumferential main grooves extending in a tire circumferential direction, a plurality of land portions partitioned by the circumferential main grooves, a narrow groove extending in the tire circumferential direction and disposed in an edge portion of a road contact surface side and an outer side in the tire width direction of the shoulder land portion on an outermost side in a tire width direction, and a narrow rib that is partitioned by the narrow groove. The narrow rib includes an offset portion having a road contact surface offset inward in a tire radial direction from the road contact surface of the shoulder land portion, and a protrusion protruding in the tire radial direction from the offset portion, extending in the tire circumferential direction, and having a top surface that is substantially flush with a profile line of the shoulder land portion.
1. A pneumatic tire comprising:
a plurality of circumferential main grooves extending in a tire circumferential direction,
a plurality of land portions partitioned by the circumferential main grooves,
a narrow groove extending in the tire circumferential direction and disposed in an edge portion of a road contact surface side and an outer side in the tire width direction of a shoulder land portion on an outermost side in a tire width direction, and
a narrow rib, as a wear sacrifice rib, that is partitioned by the narrow groove; wherein
the narrow rib includes:
an offset portion having a road contact surface offset inward in a tire radial direction from the road contact surface of the shoulder land portion, and
a protrusion protruding in the tire radial direction from the offset portion, extending in the tire circumferential direction, and having a top surface that is substantially flush with a profile line of the shoulder land portion, wherein the protrusion is disposed on the edge portion on an inner side in the tire width direction of the offset portion.
2. The pneumatic tire according to claim 1 , wherein a width W 2 of the narrow rib and a width W 1 of the road contact surface of the shoulder land portion have a relationship such that 0.20≦W 2 /W 1 ≦0.40.
3. The pneumatic tire according to claim 1 , wherein a width W 3 of the top surface of the protrusion and a width W 2 of the narrow rib have a relationship such that 0.10≦W 3 /W 2 ≦0.40.
4. The pneumatic tire according to claim 1 , wherein a distance δ between the top surface of the protrusion and the road contact surface of the shoulder land portion is within a range of −0.5 mm≦δ≦0.5 mm.
5. The pneumatic tire according to claim 1 , wherein an offset amount g between the road contact surface of the offset portion and the road contact surface of the shoulder land portion is within a range of 0.5 mm≦g≦3.0 mm.
6. The pneumatic tire according to claim 1 , wherein a groove width d of the narrow groove is within a range of 0.1 mm≦d≦4.0 mm; and a groove depth h of the narrow groove, with respect to a groove depth H of the circumferential main groove partitioning the shoulder land portion, is within a range of 0.80≦h/H≦1.10.
7. The pneumatic tire according to claim 1 , wherein a width W 4 of a portion of the road contact surface of the offset portion that is substantially parallel to the profile of the shoulder land portion has a relationship with respect to a width W 2 of the narrow rib such that 0.1≦W 4 /W 2 ≦0.7.
8. The pneumatic tire according to claim 7 , wherein the width W 4 is within a range of 5 mm≦W 4 ≦11 mm.
9. The pneumatic tire according to claim 1 , wherein a width W 3 of the top surface of the protrusion is configured to be within a range of 1 mm≦W 3 ≦3 mm.
10. The pneumatic tire according to claim 1 , wherein a width W 2 of the narrow rib is configured to be within a range of 8 mm≦W 2 ≦12 mm.
11. The pneumatic tire according to claim 1 , wherein the top surface of the protrusion has a planar form.
12. The pneumatic tire according to claim 1 , wherein when viewed as a cross-section in the tire meridian direction, the protrusion has a semicircular cross-section.
13. The pneumatic tire according to claim 1 , wherein when viewed as a cross-section in the tire meridian direction, the protrusion has an arc shaped top surface.
14. The pneumatic tire according to claim 1 , wherein:
a width W 2 of the narrow rib and a width W 1 of the road contact surface of the shoulder land portion have a relationship such that 0.20≦W 2 /W 1 ≦0.40;
a width W 3 of the top surface of the protrusion and a width W 2 of the narrow rib have a relationship such that 0.10≦W 3 /W 2 ≦0.40; and
a width W 4 of a portion of the road contact surface of the offset portion that is substantially parallel to the profile of the shoulder land portion has a relationship with respect to a width W 2 of the narrow rib such that 0.1≦W 4 /W 2 ≦0.7.
15. The pneumatic tire according to claim 14 , wherein:
the width W 2 of the narrow rib is within a range of 8 mm≦W 2 ≦12 mm;
the width W 3 of the top surface of the protrusion is within a range of 1 mm≦W 3 ≦3 mm; and
the width W 4 is within a range of 5 mm≦W 4 ≦11 mm.
16. The pneumatic tire according to claim 1 , wherein a width W 4 of a portion of the road contact surface of the offset portion that is substantially parallel to the profile of the shoulder land portion has a relationship with respect to a width W 2 of the narrow rib such that 0.47≦W 4 /W 2 ≦0.7.
17. The pneumatic tire according to claim 1 , wherein a width W 3 of the top surface of the protrusion and a width W 2 of the narrow rib have a relationship such that 0.17≦W 3 /W 2 ≦0.25.
18. The pneumatic tire according to claim 2 , wherein a width W 3 of the top surface of the protrusion and a width W 2 of the narrow rib have a relationship such that 0.10≦W 3 /W 2 ≦0.40.
19. The pneumatic tire according to claim 18 , wherein a distance δ between the top surface of the protrusion and the road contact surface of the shoulder land portion is within a range of −0.5 mm≦δ≦0.5 mm.
20. The pneumatic tire according to claim 19 , wherein an offset amount g between the road contact surface of the offset portion and the road contact surface of the shoulder land portion is within a range of 0.5 mm≦g≦3.0 mm.
21. The pneumatic tire according to claim 1 , wherein when viewed as a cross-section in the tire meridian direction, the narrow groove inclines toward the outer side in the tire width direction in a groove depth direction.