| 摘要 |
PROBLEM TO BE SOLVED: To restrain occurrence of edge wear by gradually-increasing twist in both groove wall surfaces ranging from a tread surface to a groove bottom in a straight shape main groove and making half of a groove part formed by both the groove wall surfaces a zig-zag-shaped bent groove in the circumferential direction. SOLUTION: The tread surface 1 of a tread part forms one or more linear grooves 2 with a tread surface width center E which meets the equatorial surface E of a tire put between respectively. The linear grooves 2 have groove edges which repeat far and near in a straight form with regard to the width center E at both the groove edges. A linear groove 2 is constituted so that both the sides groove wall surfaces gradually-twist in the circumferential direction from the tread surface 1 toward the groove bottom and the twisting degree is gradually-increased toward the groove bottom. Therefore, both the sides groove wall surface from the groove bottom to groove depth up to 50% of the linear main groove 2 is made a zig-zag-shaped bent groove in the circumferential direction. Branch grooves 3, 4 which extend toward the width center E are fitted, thus forming a bent rib. A traverse groove 5 which is connected with the main groove 2 is fitted in the external area of the rib 6. |
