Patent ID: 8622107

Claim:
A pneumatic runflat tire including a carcass extending from a tread portion to bead cores in bead portions through sidewall portions, and a tread-reinforcing cord layer disposed radially outward of the carcass and in the tread portion, wherein in the meridian cross section including the rotational axis of the tire in a normal inner pressure condition that the tire is mounted on a normal rim and inflated to a normal inner pressure, the outer surface of the tire has a curved profile composed of a plurality of circular arcs having different radii of curvature, the carcass comprises a carcass ply in which carcass cords are arranged at an angle of 45 to 90° with respect to a circumferential direction of the tire and are covered with a topping rubber, and an aramid fiber is used for the carcass cords, and the carcass cords have a two-bundle twisted structure that two bundles of first-twisted filaments are subjected to final twist, a total nominal dtex (fineness) D of the carcass cord is not less than 2200 dtex, and the carcass cords have a twist factor T of 0.6622 to 0.7 represented by the equation (1): T=N ×√{square root over ({(0.125 ×D/ 2)/ρ})}×10 −3 (1) in which N is the number of final twists per 10 cm, D is the total nominal dtex (fineness) of a cord, and ρ is a specific gravity of a cord material.