| 摘要 |
PURPOSE:To improve the life of a tire in the tire having a lug block type tread pattern by forming sub-grooves on both sides of each groove bottom of sub-lug grooves and circumferential grooves. CONSTITUTION:Sub-grooves 4 having a depth (h) and a groove width (b) are provided on both sides of each groove bottom of sub-lug grooves 2 which, together with main lug grooves 1, form blocks on a tread face and circumferential grooves 3. In this case, the depth (h) is set at 20-60% the depth (d) of the sub-lug groove 2 and circumferential groove 3 while setting the groove width (b) at 10-25% the groove width (a) of the sub-lug groove 2 and circumferential groove 3. Thus, by providing specified sub-grooves, the force applied from a road surface can be prevented from concentrating on the main lug grooves while restraining the generation of GC on the groove bottom and, further, the ground contacting area of the tread face can be increased by projecting portions formed by the sub-grooves increasing the life of a tire. Also, the biting in of a stone can be prevented, preventing tread separation. |
