A run-flat tire includes a side reinforcing rubber provided in a tire side portion. The run-flat tire is formed of a resin material, has a prescribed width in the tire width direction, and is provided with a reinforcing ring portion having an annular shape along the tire circumferential direction. The reinforcing ring portion is provided outside the tire radial direction of a carcass, and an elastic modulus of the reinforcing ring portion of the central region in the tire width direction is higher than an elastic modulus of the reinforcing ring portion in either position of the shoulder regions in the tire width direction.

A radial tire (1) for a heavy-duty vehicle of construction plant type, and aims to increase the rupture strength of the hoop reinforcement thereof having circumferential layers, ensuring satisfactory endurance of the crown reinforcement thereof. According to the invention, the at least one circumferential hooping layer (71, 72) comprises a median portion (711, 721) having a median width (L11, L21) and a median tensile elastic modulus (E11, E21), and two lateral portions (712, 722) that axially extend the median portion (711, 721) on either side and each have a lateral width (L12, L22) and a lateral tensile elastic modulus (E12, E22), the lateral width (L12, L22) is at least equal to 0.05 times the median width (L11, L21), and the lateral tensile elastic modulus (E12, E22) is at most equal to 0.9 times the median tensile elastic modulus (E11, E21).

A cord of a band of a tire has a single-stranded structure in which steel filaments are stranded, and the number of the filaments is not less than three and not greater than six. In a cross-section of the cord, when represents a diameter of a smallest circle that surrounds cross-sections of the filaments, and represents a diameter of each filament, a gap is formed between the filaments such that the diameter is not less than three times the diameter and not greater than six times the diameter in the case of the number of the filaments being three or four. An initial elongation of the cord is not less than 0.1% and not greater than 1.5%.