| 摘要 |
PURPOSE:To enhance the life of a tire having zig-zag tread grooves, by forming a deep bottom part along one side wall of each tread groove and a shallow and flat bottom pat along the other side wall thereof so that each groove has a stepped bottom. CONSTITUTION:The entire depth Da of a deep groove bottom part 14 is selected to be equal to that of tread grooves in conventional tires, and the difference between the former depth Da and the depth Da of a shallow groove bottom part 13, that is, the height A of the shallow bottom part 13 from the deep groove bottom part 14, is set to be 20-50% of the entire depth Da of the deep groove bottom part 14. Further, the width B of the shallow groove bottom 13 is set to be 20-80% of the entire groove width W but 100-200% of the width C of the local groove having the deep groove bottom part. With this arrangement, it is possible to restrain the pneumatic tire from being unevenly worn and to enhance the drive-out of stones, thereby the life of the tire is prolonged. |
