| 摘要 |
PURPOSE:To reduce the distortion of the groove bottom portions of lateral grooves so as to prevent cracks to be generated by properly partitioning both shoulder areas of a tread into blocks by lateral grooves and as well specifying the angles made by respective center lines of the lateral groove and a circumferential groove. CONSTITUTION:A pair of zigzag circumferential grooves 23 are formed in the circumferential direction on the tread surface portion of a tyre 21. With this arrangement, a tread 22 is tyre-axially partitioned into a central area 22a and both shoulder areas 22b. In the central area 22a, two kinds of sub-grooves 25, 26 in the tyre width direction are provided so as to partition the central area 22a into plural blocks 27. On the other hand, in both shoulder areas 22b, lateral grooves 28 which are composed of cross direction groove portions 28a extending in the nearly tyre axial direction on the tread end 22c sides and oblique direction groove portions 28b which are connected to the groove portions 28a and extend in the tyre circumferential direction on the center side of the tread 22 and end at the circumferential grooves 23 are formed. The groove angles theta1, theta2 of supplementary angles made by respective centers of the oblique direction groove portion 28b and the circumferential groove are set within a range of 130-160 deg.. |
