| 摘要 |
PURPOSE:To improve the performance of a tire at the time of traveling on both unleveled ground and leveled-ground road by quartering the pitch between the centers in circumferential direction of adjacent grooves in the center of a tread and setting the negative comparison value of each zone at below a defied value. CONSTITUTION:One pitch P between each center in the circumferential direction of adjacent grooves 15A, 15B in the center 12b of a tread 12 is quartered to form four zones 12A-12D. Out of the area ratios (negative ratios M) of the grooves 15A, 15B and circumferential grooves 17 of each zone 12A-12D to the whole area, the ratio of the maximum negative ratio to the minimum negative ratio (in the figure, 12A and 12D are the maximum and 12b and 12C are the minimum), i.e., a negative comparison value R is specified to be below 1.22. By this structure, vibration-riding quality performance can be improved by reducing the change in negative ratio in one pitch. Also, traction performance, slide-slip performance, and tire life can be ensured. |
