Sughrue, Mion, Zinn, Macpeak & Seas, PLLC
Pneumatic tire having sipe structured by narrow groove portion and wide groove portion
 A sipe formed in a block is structured, in a depthwise direction of the sipe, by a narrow groove portion formed at a ground-contact surface side of the sipe and a wide groove portion formed at a bottom portion side of the sipe and wider than the narrow wide portion. A portion connecting the narrow groove portion and the wide groove portion is inclined along a longitudinal direction of the sipe. When a pneumatic tire having a tread surface on which such blocks are formed is worn, wear proceeds as follows. At an initial stage of wear during which draining performance of main grooves is excellent, only the narrow groove portion is exposed so that noise is suppressed. At an intermediate stage of wear during which draining performance of the main grooves deteriorates, the wide groove portion is gradually exposed, and the draining performance of the sipe improves to compensate for deterioration of the draining performance of the main grooves. At a final stage of wear, only the wide groove portion remains, and because a depth of the sipe is small, noise is suppressed. In this way, noise can be suppressed until the final stage of wear of the tire, and at the same time, deterioration in wet performance of the tire can be suppressed. 
Bridgestone Corporation
B B Y B Y B
B60C B60C Y10S B60C Y10S B60C
inventional inventional additional inventional additional inventional
Shinichi
Watanabe