| 摘要 |
PURPOSE:To reduce the occurrence of cracks by setting a ratio of the height from the sipe bottom to the sipe depth to a specified range. CONSTITUTION:A corrugated portion of a sipe 4 is provided within the range of the height A=A1+A2=0.3<A/L<0.6 from the sipe bottom to the sipe depth L. In A/L<= 0.3, the range formed with the corrugated portion is deficient so that an effect of reducing a deformation amount of a block is not obtained and reversely the provision of the corrugated portion in the range of A/L >=0.6 does not contribute to the reduction of cracks. However, when the corrugated portion of the sipe 4 is formed on the sipe bottom, stress is apt to unevenly concentrate on the sipe bottom, so that the sipe bottom is preferably provided with a straight portion to avoid the uneven concentration. Also, in the corrugated portion of the sipe 4, the ratio of a wave form amplitude C to the sipe width T is set to the range of 1.5<=C/T<=3.0. |
