Abstract: A pneumatic radial tire having a tread formed from a rubber strip-stacked body by stacking rubber strip layers composed of a rubber strip wound spirally while continuously joining side surfaces thereof to each other in a tire circumferential direction on the outside of a carcass layer via a belt layer, in which boundary surfaces of the rubber strip of the rubber strip-stacked body forming at least an outermost layers of both shoulder portions of the tread are leaned respectively toward the outside of a tire diameter direction relative to a tire outside direction in a tire width direction.

Abstract: In a heavy duty pneumatic radial tire, at least one carcass layer is provided between right and left bead portions and at least two belt layers formed of steel cords which exhibit a breaking elongation of 4% or less are arranged in an outer periphery of the carcass layer in a tread portion. The belt layers are composed of at least one upper belt layer (A) and at least one lower belt layer (B). The upper belt layer (A) has a belt width that is 0.6 times or less a carcass line maximum width SW of the carcass layer at a tire section and the lower belt layer (B) has a belt width such that both end portions thereof extend to tread shoulder portions. An inclination angle of the steel cords of the lower belt layer (B) relative to a tire circumferential direction is set to be larger than that of the upper belt layer (A). A ratio (Mb.sub.2 .multidot.N.sub.2)/( Mb.sub.1 .multidot.N.sub.1) of a product of a bending rigidity Mb.sub.2 per steel cord of the lower belt layer (B) and the number N.sub.