| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve performance on ice and snow by suppressing increase in ground contact pressure at both side edge portions of a circumferential main groove. <P>SOLUTION: At least one groove wall of the circumferential main groove is a constricted groove wall having a constricted portion which projects to a direction for reducing a groove width. The constricted wall comprises: a groove wall portion at a groove bottom side, which extends from a groove bottom to the constricted portion; and a groove wall portion at a tread surface side, having groove width increasing tilt which tilts and extends to a groove width increasing direction from the constricted portion to a tread surface. Height h of the constricted portion from the groove bottom is within the range of 10 to 50% of a groove depth H. The groove wall portion at the groove bottom side includes a groove width decreasing tilt portion which tilts to a groove width decreasing direction toward a tread surface, and which is connected to the constricted portion. A maximum angle θsmax of an angle θs with respect to a normal of the tread surface in the groove width decreasing tilt portion, is larger than an angle θt with respect to the normal of the tread surface in the constricted portion of the groove wall portion at the tread surface side. <P>COPYRIGHT: (C)2012,JPO&INPIT |
