Patent ID: 6125899
Filing Date: 2000-10-03
Classification: B60C,Y10T

Abstract:
A heavy duty pneumatic radial tire for running on rough ground surfaces comprising:at least one carcass layer being provided between right and left bead portions; and at least two belt layers formed of steel cords arranged in an outer periphery of said at least one carcass layer in a tread portion, said steel cords exhibiting a breaking elongation of 4% or less, wherein said belt layers comprise at least one upper belt layer (A) and at least one lower belt layer (B), said at least one upper belt layer (A) having a belt width that is 0.6 times or less of a carcass line maximum width SW at a tire cross-section and said at least one lower belt layer having a belt width such that both end portions thereof extend to tread shoulder portions, an inclination angle of the steel cords of said at least one lower belt layer (B) relative to the tire circumferential direction is set to be larger than that of said at least one upper belt layer (A), and a ratio r=(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 said at least one lower belt layer (B) and the number N.sub.2 of the steel cords per unit width of said at least one lower belt layer (B) to a product of a bending rigidity Mb.sub.1 per steel cord of said at least one upper belt layer (A) and the number N.sub.1 of the steel cords per unit width of said at least one upper belt layer (A) is set to be at a range of 0.2 to 0.65.