Abstract: Provided is a tire such that both tire weight reduction and high durability can be achieved by establishing a technology capable of ensuring the sufficient effect of preventing diameter growth even when the amount of steel used in a belt layer is decreased. The tire includes: two or more crossing belt layers 4 including rubberized layers of steel cords tilting and extending at an angle of 10° to 30° with respect to a tire equatorial plane, the rubberized layers being arranged such that the directions of the cords intersect each other; and a high-angle bell layer 3 including a rubberized layer of steel cords tilting and extending at an angle which is 5° or more greater than the angle of the crossing belt layers.

Abstract: This invention provides a pneumatic tire having its weight reduced without degrading the durability of bead portions. Provided is a pneumatic tire comprising, as a framework, at least one carcass ply comprising a steel cord covered with rubber. Letting d (mm) be the cord diameter of the steel cord and T (MPa) be the tensile strength of a steel filament forming the steel cord, the following relation is satisfied: a1T?b1>d>a2T+b2 (where a1 is 3.65×10?4 mra/MPa, b1 is 0.42 mm, a2 is ?8.00×10?5 mm/MPa, and b2 is 0.78 mm), and the tensile strength T of the steel filament is 3000 MPa (exclusive) to 4000 MPa (exclusive) and the number of hits E under a bead core of the steel cord in the carcass ply is 12 hits/25 mm (exclusive) to 38 hits/25 mm (exclusive).

Abstract: Provided by the present invention is a technique which can, in a pneumatic radial tire using corrugated steel cords in the circumferential bent, improve the durability of the corrugated steel cords in order to prevent fatigue rupture thereof caused by an increase in energy input. The present invention is a pneumatic radial tire which has a carcass 1 as the skeleton extending in a toroidal shape between a pair of bead portions on either side of the tire, as well as a belt layer 2 and a tread layer 5 successively arranged thereonto at the outer part in the tire radial direction. The belt layer 2 comprises at least one layer of circumferential belt 3 which comprises a plurality of corrugated or zigzag-shaped steel cords extending along the tire circumferential direction, and when the steel cords are removed from the circumferential belt 3, the bending radius of curvature (R) of the steel cords is within the range from not less than 18 mm to not more than 125 mm.