Abstract: Low profile radial tires for trucks and buses reinforced with steel cords which comprise two layers of a core and an outer layer, the number of core filaments being 3 to 4 and the number of outer filaments being equal to or less than the number 5 greater than the number of the core filaments, all filaments being substantially equal in diameter and both the core filaments and the outer filaments being twisted in the same direction with a different pitch, and the aspect ratio of the tire being at most 0.85.

Abstract: A steel cord comprises at least nine filaments which are twisted in substantially the same direction with substantially the same pitch. A coil formed by each filament has a diameter which is variable along the cord central line. Most of the filaments are interwined with one another without forming layers.

Abstract: A heavy-load radial tire, comprising three or four belt layers of steel cords laminated at a slight angle with respect to the tire circumference direction in the central part of the outside of a carcass. An intermediate belt layer adjacent to the outermost belt layer has a cord strength which is at least 1.2 times greater than that of an inscribed belt layer which is inscribed in said intermediate belt layer. The end number of the intermediate belt is reduced so that the belt strength of the intermediate belt layer is substantially equal to that of the inscribed belt layer.

Abstract: A pneumatic tire at least partially reinforced with steel cords. Most of steel filaments of said steel cords comprise iron materials having carbon content of 0.75 to 0.85 percent by weight. Said steel cords have an preferred tensile strength (TS) calculated from the following formula; ##EQU1## wherein W is the weight (g/m) of a steel cord, D is the diameter (mm) of the steel filament and N is the number of steel filaments of a steel cord and said steel cords also have a maintenance ratio of the knot strength of more than 60%.