Importance

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Abstract

A pneumatic radial tire is disclosed, which comprises a toroidal tire body extending from bead portions to a crown portion through sidewall portions, and a reinforcement for the tire body consisting of a carcass composed of at least one cord ply containing polyester fiber cords therein, which cord ply being wound around a bead core embedded in each of the bead portions from the inside of the tire to the outside thereof, and a belt composed of at least two ply layers superimposed around the crown portion of the carcass and containing cords arranged at a relatively small inclination angle with respect to the mid-circumferential plane of the tire, the cords of which being crossed with each other. In this type of the tire, the carcass line of the tire body at a mounted state of the tire on a normal rim under a normal internal pressure depicts such a radial profile in tire section that a ratio of R/R' is within a range of 0.65-0.85 in which R' is a radius of a reference arc BEC, and R is a radius of curvature of a contour curve FC in a shoulder portion of the carcass line, and that a maximum distance f between the reference arc and a contour curve in a base portion of the carcass line is within a range of 5-10 mm; and the polyester fiber cord has an elongation .DELTA.E under a tension of 2 g/d of not less than 5%, and a value of .DELTA.S+0.4.DELTA.E of not more than 5.0% in which .DELTA.S is a heat shrinkage of the cord.

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First Claim