Large-size pneumatic radial tire for use on rough road with belt having specified cord

摘要

A large-size pneumatic radial tire for use on rough road is disclosed, which comprises as a tire reinforcement a carcass ply of cords arranged in a direction substantially perpendicular to the equatorial plane of the tire and a belt composed of at least three cord layers each containing steel cords embedded parallel to each other in rubber and arranged at a relatively small angle with respect to the equatorial plane of the tire, at least a pair of adjacent cord layers among which being piled one upon the other to cross their cords with each other at an angle of 15°- 30° with respect to the equatorial plane. In this type of the tire, the outermost cord layer for the belt is a cord layer formed by embedding a plurality of twisted steel cords, each having a single layer construction of 1×3, 1×4 or 1×5 or a double layer construction with a core of 1 to 2 filaments obtained by twisting plural steel filaments shaped prior to the formation of cord, in rubber at a cord volume fraction of 5-40% so as to provide a sealing type penetration form wherein a portion of the cord having an inner space completely filled with the penetrated rubber and a length l.sub.1 is alternately connected with a portion of the cord having an inner space incompletely filled with the penetrated rubber and a length l.sub.2 in the longitudinal direction of the cord so as to satisfy l.sub.2 of not more than 10 mm and l.sub.1 /l.sub.2 of not less than 0.14.