Pneumatic tire

Abstract

A land ratio of a shoulder portion Sh of a tread portion is 57 to 72%, and a land ratio of a center portion Ce is 40 to 55%. In the center portion Ce, one row block made up of center blocks is formed. Each of the center blocks has its width gradually reduced from a position establishing an axial maximum width BW toward both a leading end and a trailing end relative to the tire rotating direction, each of the center blocks being provided with, at the leading end thereof, a tip portion that sharpens toward the leading end, and being provided with, at the trailing end thereof, a concave portion that smoothly concaves toward the leading end. In each of the center blocks, a ratio (BL/BW) between the axial maximum width BW and a maximum length BL in the circumferential direction is 1.00 to 1.20.

1 . A pneumatic tire, comprising:
 a tread portion having a tread pattern being formed by repetitive arrangement of substantially identically patterned pattern pitches in the circumferential direction of the tire, wherein   the tread portion has a center portion making up 50% of a tread ground-contact width whose center is a tire equator, and shoulder portions respectively situated on opposite sides of the center portion,   in each of the shoulder portions, shoulder main grooves extending inwardly from an outside relative to a tread ground-contact edge in the axial direction of the tire are arranged at certain intervals in the circumferential direction of the tire, whereby a shoulder land portion is established between the shoulder main grooves, a land ratio in each of the shoulder portion between the tread ground-contact edge and an outer edge of the center portion being 57 to 72%,   in the center portion, between the shoulder land portions being arranged on opposite sides in the axial direction of the tire, at least one center block row having center blocks arranged in the circumferential direction at certain intervals is provided, a land ratio of the center portion being 40 to 55%,   the center blocks are adjacent to the respective shoulder land portions, with a longitudinal groove-like portion extending in the circumferential direction of the tire being interposed therebetween, and   the longitudinal groove-like portion has a narrowed width portion whose width in the axial direction of the tire is 3 to 6 mm thereby establishing a minimum width, and increased width portions whose respective widths in the axial direction of the tire are gradually increased from the narrowed width portion toward the opposite sides in the circumferential direction of the tire.   
     
     
         2 . The pneumatic tire according to  claim 1 , wherein
 the shoulder land portions are tapered so as to be gradually reduced inward in the axial direction of the tire in their length in the circumferential direction of the tire, and   respective apexes of such tapered portions form the narrowed width portion.   
     
     
         3 . The pneumatic tire according to  claim 2 , wherein an interior angle γ of each of the tapered portions is 100 to 150 degrees. 
     
     
         4 . The pneumatic tire according to  claim 1 , wherein in each of the shoulder portions, a shoulder sub groove being smaller than each one of the shoulder main grooves in width is provided between the shoulder main grooves, so as to divide each of the shoulder land portions into two blocks. 
     
     
         5 . The pneumatic tire according to  claim 4 , wherein an inner end portion in the axial direction of the tire of each of the shoulder main grooves and an inner end portion in the axial direction of the tire of the shoulder sub groove communicate with the increased width portion. 
     
     
         6 . The pneumatic tire according to  claim 2 , wherein in each of the shoulder portions, a shoulder sub groove being smaller than each one of the shoulder main grooves in width is provided between the shoulder main grooves, so as to divide each of the shoulder land portions into two blocks. 
     
     
         7 . The pneumatic tire according to  claim 3 , wherein in each of the shoulder portions, a shoulder sub groove being smaller than each one of the shoulder main grooves in width is provided between the shoulder main grooves, so as to divide each of the shoulder land portions into two blocks.