Abstract: A heavy duty pneumatic tire comprises a radial carcass, and a belt comprised of at least three belt layers, in which a first belt layer contains cords inclined at a large cord angle with respect to an equatorial plane of the tire and each of a second belt layer and a third belt layer contains cords inclined at a small cord angle with respect to the equatorial plane and cords of the second and third belt layers are crossed with each other. In the tire, the first belt layer is comprised of steel cords having a 1.times.N structure (N: 2-5) and/or each of the second and third belt layers is comprised of steel cords obtained by twisting 6 sheath steel filaments each having a filament diameter of not more than 0.30 mm around a single core filament at a twisting angle of not more than 6.degree..

Abstract: A steel cord for the reinforcement of the carcass of a pneumatic radial tire comprises a central basic layer comprised of 1 to 4 steel filaments, at least one coaxial layer arranged around the central basic layer and comprised of many steel filaments in which these filaments are twisted in the same twisting direction at the same twisting pitch, and a wrap filament spirally wound around the coaxial layer in the same twisting direction.

Abstract: A heavy duty pneumatic tire comprises a radial carcass, and a belt comprised of at least three belt layers, in which a first belt layer contains cords inclined at a large cord angle with respect to an equatorial plane of the tire and each of a second belt layer and a third belt layer contains cords inclined at a small cord angle with respect to the equatorial plane and cords of the second and third belt layers are crossed with each other. In the tire, the first belt layer is comprised of steel cords having a 1.times.N structure (N: 2-5) and/or each of the second and third belt layers is comprised of steel cords obtained by twisting 6 sheath steel filaments each having a filament diameter of not more than 0.30 mm around a single core filament at a twisting angle of not more than 6.degree..

Abstract: A steel cord for the reinforcement of rubber articles comprises a central basic layer comprised of 1 to 4 steel filaments, at least one coaxial layer arranged around the central basic layer and comprised of many steel filaments in which these filaments are twisted in the same twisting direction at the same twisting pitch, and a wrap filament spirally wound around the coaxial layer in the same twisting direction.

Abstract: A steel cord for the reinforcement of rubber articles is disclosed, which comprises a central base structure composed of 1 to 4 steel filaments, and at least one coaxial layer composed of plural steel filaments arranged around the central base structure so as to adjoin them to each other, these steel filaments being twisted in the same direction at the same pitch. In the steel cord of this type, the steel filaments constituting the central base structure have the same diameter (dc), while at least one steel filament of the coaxial layer has a diameter (dso) smaller than the diameter (dc) of the steel filament in the central base structure.

Abstract: In a heavy duty radial tire, metal cords of a single layer construction obtained by twisting 3.about.5 metallic filaments having a filament diameter of 0.13.about.0.32 mm, each of which cords having an elongation P.sub.1 under a load of 0.25.about.5 kgf/cord of 0.35.about.1.0% as an arithmetic mean value are arranged as a carcass ply so that a distance between cords at an end of the carcass ply is not less than 0.25 mm. Thus, it is possible to largely reduce the tire weight, avoid problems on the operability such as bead rising and the like, and considerably improve the fracture resistance, corrosion fatigue resistance and fretting resistance at carcass ply end as well as resistance to external damage in sidewall (resistance to cord breaking up) of the radial tire.

Abstract: A steel cord for the reinforcement of rubber articles is disclosed, which comprises a central base structure composed of 1 to 4 steel filaments, and at least one coaxial layer composed of plural steel filaments arranged around the central base structure so as to adjoin them to each other, these steel filaments being twisted in the same direction at the same pitch. In the steel cord of this type, the steel filaments constituting the central base structure have the same diameter (dc), while at least one steel filament of the coaxial layer has a diameter (dso) smaller than the diameter (dc) of the steel filament in the central base structure.

Abstract: A steel cord for the reinforcement of rubber articles is disclosed, which comprises a central base structure composed of 1 to 4 steel filaments, and at least one coaxial layer composed of plural steel filaments arranged around the central base structure so as to adjoin them to each other, these steel filaments being twisted in the same direction at the same pitch. In the steel cord of this type, the steel filaments constituting the central base structure have the same diameter (dc), while at least one steel filament of the coaxial layer has a diameter (dso) smaller than the diameter (dc) of the steel filament in the central base structure.

Abstract: A steel cord for the reinforcement of rubber articles is disclosed, which comprises a central base structure composed of 1 to 4 steel filaments, and at least one coaxial layer composed of plural steel filaments arranged around the central base structure so as to adjoin them to each other, these steel filaments being twisted in the same direction at the same pitch. In the steel cord of this type, the steel filaments constituting the central base structure have the same diameter (dc), while at least one steel filament of the coaxial layer has a diameter (dso) smaller than the diameter (dc) of the steel filament in the central base structure.

Abstract: A pneumatic radial tire is disclosed, which comprises steel cords having a two or three layer construction represented by a designation of l+m or l+m+n as a tire reinforcement, wherein two layers at a center side of a transverse section in the steel cord have the same twisting direction but different twisting pitches. In this steel cord, m filaments constituting an outer layer are arranged so as to enter into an inside of a circumscribed circle enveloping l filaments of an inner layer at a non-contact region above a predetermined value and have a form ratio of 90-110%.

Abstract: A pneumatic radial tire having an improved durable life is disclosed. In the pneumatic radial tire, a metal cord used in the carcass ply is characterized by having a layer construction of 3+9+1 wherein three filaments are twisted together to form a core, nine filaments each having the same diameter as in the filament for the core are twisted around the core to form a second layer and a single filament is wrapped around the second layer, and limiting a twisting angle .alpha. of the second layer to a range of 72.0.degree..ltoreq..alpha..ltoreq.78.0.degree..