| 摘要 |
A pneumatic radial tire including a plurality of main grooves so formed on a tread surface of a tread portion as to extend in a tire circumferential direction and ribs defined by said main grooves, characterized in that a thin groove extending inward and obliquely is formed on a transverse side surface of shoulder portion of the tread portion in the tire circumferential direction, a ground non-contacting rib protruding from the transverse side surface is formed inside the thin groove in a radial direction in such a manner as to be separated by the thin groove, and angle alpha of the transverse side surface to a normal of a plane S inclusive of the tread surface is from 20 DEG to 60 DEG , an angle beta of the thin groove to the normal of the plane S describes a line having an angle of 10 DEG to 50 DEG , and a vertical distance h of the groove bottom of the thin groove from the plane S, a groove depth d of the main groove and a vertical distance g of the top surface of the ground non-contacting rib from the plane S satisfy the relation h/d=0.5 to 1.2 and g/h=0.5 to 0.8.
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