Abstract: A pneumatic radial tire for heavy loads, formed by providing the shoulder side edge portions of at least the second inner ribs or block rows counted from the outermost parts of a tread portion with narrow ribs of a height equal to that of the ribs or block rows via narrow grooves, and chambering the edge portions of these narrow ribs or inclining the depthwise axes of these narrow grooves from a tread surface toward a tread center.

Abstract: 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.degree. to 60.degree., an angle .beta. of the thin groove to the normal of the plane S describes a line having an angle of 10.degree. to 50.degree.

Abstract: A pneumatic radial tire for heavy loads having block type tread pattern defined by a plurality of grooves provided on a tread surface thereof and by a plurality of blocks segmented and formed by the plurality of grooves, characterized in that each of at least such ones of the plurality of grooves which traverse the plurality of blocks in a width direction of the tire, having a sectional shape on each side of the groove, taken in a direction crossing the groove, the sectional shape of the grooves, comprises: a slanted linear line positioned on a bottom side of the groove and expanding outwardly toward the tread surface; and a circular arc line positioned on a side of the tread surface, an inward end of which contacting the linear line, and an outward end of which contacting the tread surface.

Abstract: A pneumatic radial tire formed so that, when the tire is inflated from a non-inflated state, in which the inner pressure thereof is 5% of a normal lever, to a normal inner pressure, a central region of the outer surface of the tread in a meridional cross section of the tire which is between two points P.sub.1, P.sub.1 ' spaced from the center P.sub.0 of a tread width to left and right along the outer surface of the tread by a distance L, which is expressed by the formula 0.25TW.ltoreq.L<0.50TW, with respect to a width TW of a ground contacting portion of the bread grows outward in the radial direction of the tire, shoulder regions on both outer sides of the two points P.sub.1, P.sub.1 ' contracting inward in the radial direction of the tire, with a radius of curvature R.sub.2 of a region, which is formed between two intermediate points P.sub.2, P.sub.2 ', which are positioned halfway respectively between the center P.sub.