| 摘要 |
PURPOSE:To improve driveability on a frozen and iced road surface in a studless tire by forming narrow and wide land parts of narrow grooves making a predetermined inclination to the widthwise direction of tread in a land division formed on the tread to ensure a ground contacting region contact area with the high regidity of the wide width land part. CONSTITUTION:In land divisions 4 defined on a tread surface 1 by a main groove 2 and sub-grooves 3 are formed narrow width land parts 6a,6b defined by narrow grooves 5a,5b in bending deformation regions and wide width land parts 7a,7b providing shearing deformation regions. Then, the narrow groove 5a in the central region of the tread surface 1 is inclined 30 deg. or less of inclination theta1 to the widthwise direction of the tread surface 1. Also, the narrow groove 5b in the end of the tread surface 1 is set to at least 60 deg. of similar inclination theta2. Further, the thickness TS of the narrow width land parts 6a,6b is set to 0.1-0.5 times the depth h of the narrow grooves 5a,5b and the thickness TL of the wide width land parts 7a,7b are set to at least 0.78 times the depth h of the narrow grooves 5a,5b. Further, the dimension TB between groove bottom of respective land divisions 4 is specified to at least 1.5 times the dimension H-h between the groove bottoms of the narrow grooves 5a,5b and the groove bottoms of mutually divided grooves 2,3. |
