Run-flat tire

A run-flat tire (1) with an aspect ratio of 50% to 60%, which comprises a carcass (6) consisting of a single ply of cords extending between bead cores (5) through a tread portion (2) and sidewall portions (3), a pair of sidewall reinforcing layers (10) 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 (8) extending radially outwardly of the tire from bead cores, each bead apex element having a height (Hb) of from 0.30 to 0.48 times a tire section height (Ho) from a bead base-line (BL), wherein the tire has certain relations with respect to thicknesses of sidewall reinforcing layers and sidewall rubber elements.