Abstract: A process for producing a pneumatic tire having high uniformity with a carcass ply formed of polyester cord, including the steps of: (a) spinning polyester at a tension at the solidifying point of melt polyester between 1.5.times.10.sup.7 and 7.5.times.10.sup.7 dyne/cm.sup.2 ; (b) drawing the polyester into a filament at a draw ration of 2.0 to 3.0; (c) twisting a polyester filament at a twist coefficient of from 800 to 2,500; and then (d) heat treating the filament so that the dimension unstabilizing factor is 8.5 or less. The polyester filament is made of polyester having an ethylene terephthalate component of at least 85 mol % and a high degree of polymerization such that the intrinsic viscosity is at least 0.8, and the ratio of the birefringence of the surface portion to that of the central portion in the polyester filament is from 1.03/1 to 1.15/1; the twist coefficient is represented by T.times..sqroot.

Abstract: A process for producing a pneumatic tire having high uniformity with a carcass ply formed of polyester cord, including the steps of: (a) spinning polyester at a tension at the solidifying point of melt polyester between 1.5.times.10.sup.7 and 7.5.times.10.sup.7 dyne/cm.sup.2 ; (b) drawing the polyester into a filament at a draw ration of 2.0 to 3.0; (c) twisting a polyester filament at a twist coefficient of from 800 to 2,500; and then (d) heat treating the filament so that the dimension unstabilizing factor is 8.5 or less. The polyester filament is made of polyester having an ethylene terephthalate component of at least 85 mol % and a high degree of polymerization such that the intrinsic viscosity is at least 0.8, and the ratio of the birefringence of the surface portion to that of the central portion in the polyester filament is from 1.03/1 to 1.15/1; the twist coefficient is represented by T.times..sqroot.

Abstract: A radial tire for heavy duty use in vehicles. The tire has a carcass having a two-ply structure using polyester cords of more than 4500d as the ply cords. The spacing of the cords between the first and second plies at approximately the maximum tire width, is nearly 1.2-1.7 times as large as cord diameter. The edge portions of the ply cords turned up around bead cores are coated with the same rubber as ply coating rubber, an extension of the edge covering rubber from the edge of the ply cords is three times or more as large as cord diameter.