Abstract: An off-the-road heavy duty pneumatic radial tire running on severely rough roads comprises a rubber reinforcing layer having a partial crescent shape in section and a JIS hardness of 55.degree..about.75.degree. and a particular thickness distribution over a range from the bead portion to the vicinity of the belt end portion as a reinforcement for the sidewall portion, whereby the stable running performances and the carcass durability in bead portion can simultaneously be improved to give good resistance to lateral rolling and followability on uneven road surface to the vehicle running on rough roads.

Abstract: A tread pattern of two main groove-rib type provided with auxiliary grooves having excellent stone-biting resistance and stone-expelling property is disclosed. In the tread pattern, a pair of main grooves are disposed near both side edges of the tread along these edges and one or two pairs of auxiliary grooves are oppositely arranged between the main grooves, wherein the bottom of the auxiliary groove is directed to the center of the tire in such a manner that the center line in radial section of the auxiliary groove is inclined at an angle of 5.degree.-20.degree. with respect to a normal line of the tread drawn from an intersection of the center line and the tread.