A rubber-reinforcing steel cord embedded in a rubber product has a stranded structure including a core strand, and a plurality of sheath strands intertwined around an outer circumferential surface of the core strand; wherein a lubricant is provided between wires that constitute the core strand.

A rubber-reinforcing steel cord embedded in a rubber product has a stranded structure including a core strand, and a plurality of sheath strands intertwined around an outer circumferential surface of the core strand; wherein a lubricant is provided between wires that constitute the core strand.

Provided is a steel cord for reinforcing rubber articles which, when applied to a belt of a tire, can attain lightweight without reducing the durability of the tire, and in particular, to a steel cord for reinforcing rubber articles in which the properties of a treat after rubberizing are excellent and a pneumatic radial tire using the same. Also provided is a steel cord for reinforcing rubber articles comprising a core formed by arranging two core filaments 1 in parallel without being twisted together, and N (2N4) sheath filaments 2 which are twisted together around the core. Letting the diameter of the core filament 1 be d1, and the diameter of the sheath filament 2 be d2, d1>d2.

Disclosed is a tire-reinforcing steel cord for a radial tire. The tire-reinforcing steel cord has a double layer structure including a first-layer core and a second-layer core provided on the surface of the first-layer core. The first-layer core has an elliptical or rectangular cross section. The tire-reinforcing steel cord can improve processability, fatigue characteristics, and rolling resistance performance of a tire, resulting in improved fuel efficiency. A radial tire using the tire-reinforcing steel cord is also disclosed.

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. The mass of the steel cords per unit area included in the high-angle belt layer is 85% or less of the mass of the steel cords per unit area included in the crossing belt layers, and compressive rigidity per unit area in a cross section orthogonal to the longitudinal direction of the steel cords of the high-angle belt layer is greater than compressive rigidity per unit area in a cross section orthogonal to the longitudinal direction of the steel cords of the crossing belt layers.