Pneumatic tires

A radial carcass tire whose sidewalls are formed, at least on the outer surface layer thereof, of at least one surface layer mixture comprising nonhalogenated elastomers both of the diene type selected from the group consisting of natural rubber, polybutadiene, polyisoprene, styrene-butadiene copolymer and transpolypentene mixed with an ethylene-propylene type selected from the group consisting of ethylene-propylene copolymer and ethylene-propylene-diene terpolymer containing on the order of 5% diene, characterized by the fact that the outer surface layer portions of the sidewalls formed of said mixes are vulcanized by means of an organic peroxide, the amount of organic peroxide used being from about 1 to about 10 parts by weight per 100 parts by weight of elastomers of a commercial organic peroxide containing 40% by weight of active product, said sidewalls having high flexure fatigue resistance, said outer surface layer portions having a thickness at least about one fourth the thickness of the sidewalls, said mixture containing from about 30 to about 65 parts by weight of carbon black per 100 parts by weight of elastomers, and the amount of said elastomer of the ethylene-propylene type used being between about 15% and about 60% by weight of the total of the elastomers.