Run-flat tire

A run-flat tire comprising a radial carcass composed of one or more carcass plies extending toroidally between bead cores embedded in a pair of bead portions, at least one layer of belt arranged at the outer part of the radial carcass in the tire radius direction, and provided with a tread portion arranged at an outer part of a crown portion of the radial carcass in the tire radius direction, a pair of buttress portions positioned at both ends of the tread portion and a pair of side portions connecting the buttress portion and the bead portion, wherein a pair of crescent cross-sectional side reinforcing rubber layers are arranged at the inner part of the radial carcass extending from the buttress portion to the side portion, characterized in that

• the tire is provided with a reinforcing cord layer adjoining the radial carcass at least from the belt end to the maximum width portion of the tire side portion;
• cords constituting the reinforcing cord layer are selected from the group consisting of nylon 66 cord, cellulosic fiber cord, polyethylene terephthalate cord, polyethylene naphthalate cord and aramid/nylon 66 hybrid cord, and has a cord angle of less than 10° with respect to the tire radius direction;
• and
• the elastic modulus of the cord pulled out from the tire at a temperature of 25° C. under the conditions of a load of 3 N is not higher than 40 cN/dtex, and the thermal shrinkage stress σ (cN/dtex) at a temperature of 177° C. and the elastic modulus E (cN/dtex) at a temperature of 177° C. under the conditions of a load of 10 N satisfy the following conditions:
• σ+0.025E≧0.36, 40≧E≧8, and σ≧0.05.