A run-flat tire with an aspect ratio of 50% to 60%, which comprises a carcass consisting of a single ply of cords extending between bead cores through a tread portion and sidewall portions, a pair of sidewall reinforcing layers each with a crescent cross-sectional shape and disposed axially inwardly of the carcass in each sidewall portion, the sidewall reinforcing layers made of rubber having a complex elastic modulus of from 6 to 12 MPa, and a pair of bead apex elements which extending radially outwardly of the tire from bead cores, each bead apex element having a height of from 0.30 to 0.48 times a tire section height from a bead base-line, wherein the tire has certain relations with respect to thicknesses of sidewall reinforcing layers and sidewall rubber elements.