Abstract: 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.degree.-30.degree. 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.times.3, 1.times.4 or 1.times.

Abstract: A pneumatic radial tire comprising a belt portion disposed between the tread portion and the carcass portion wherein the belt portion is constituted by at least a pair of first belts, a second belt and a third belt which are arranged from radially inward to outward, the first, second and third belts having a first series, second series and third series of parallel cords embedded therein, respectively. The first belts being laterally spaced apart a predetermined lateral space symmetrically with respect to the mid-circumferential centerline and the cords thereof are disposed at an angle of between 40 to 60 degrees with respect to the mid-circumferential centerline. The spaced-apart first belts have opposite lateral ends which are located within less than 5 percent of a belt width of the third belt from the corresponding opposite lateral ends of the third belt, respectively.

Abstract: A pneumatic radial tire having an improved durability in the running on bad road is disclosed, which comprises a carcass composed of at least one rubberized cord ply containing cords arranged substantially perpendicular to the equatorial plane of the tire and a belt superimposed around the crown portion of the carcass and composed of at least two rubberized cord layers each containing cords inclined at a relatively small angle with respect to the equatorial plane of the tire, the cords of which being crossed with each other. In this tire, the outermost layer of the belt contains cords having a flexural rigidity lower than that of the remaining layer and arranged at an end count higher than that thereof.