Pneumatic radial tires

In a pneumatic radial tire having an aspect ratio of no more than 60% and comprising at least one carcass ply composed of a main body portion extending between a pair of bead cores each embedded in the respective bead portion and a turn-up portion wound outward around each bead core in a radial direction of the tire, a stiffener arranged between the main body portion and the turn-up portion on an outside of the bead core in the radial direction of the tire, extending outward in the radial direction of the tire, and made of a soft rubber stock and a hard rubber stock, and a reinforcing member extending at an outside of the turn-up portion in a widthwise direction of the tire through a cushion rubber, the improvement wherein when the tire is inflated under an air pressure corresponding to 10% of a maximum air pressure, a height of an outer end of the turn-up portion in the radial direction is no more than 0.33 times a section height of the carcass ply, and a ratio of a thickness between the main body portion and the reinforcing member to a thickness between the main body portion and the outer end of the turn-up portion in the radial direction as measured on a normal line drawn from the outer end of the turn-up portion in the radial direction onto an outer surface of the main body portion is within a range of 1.2-1.8.