BLOCK PATTERN TIRE WITH OPTIMIZED GROOVE DEPTH RATIOS, SIPE DEPTH AND LENGTH RATIOS

摘要

A block pattern tire is provided herein. It comprises a tread portion provid ed in the central part with a circumferential row of blocks which are divided by two wide main circumferential grooves and axial grooves extending therebetween. The thread portion is provided, in its tread surface, with a plurality of first sipes which are narrower than the circumferential grooves, and axial grooves. The axial grooves are shallower than the circumferential grooves. Each of the axial grooves is provided, in the botto m face thereof, with a second sipe having a width of 0.2 to 1.1 mm, the second sipe extendin g along the centre line of the axial groove and having ends terminated within the bottom so as to have a length of not less than 0.7 times and less than 1.0 times the axial groove length. The depth of the axial groove is in the range of 0.2 to 0.5 times the depth of the circumferential grooves. The depth of the second sipe is 0.2 to 0.5 times the depth of the circumferential grooves. The total of the depth of the axial groove and the depth of the second sipe is not more than 0.7 times the depth of the circumferential grooves.