The run flat tire according to this disclosure comprises a tread portion, sidewall portions, bead portions, a side-reinforcing rubber, and a carcass. An inner liner is provided on the tire inner surface, and an inner layer rubber is disposed between the side-reinforcing rubber and the inner liner. In accordance with JIS K6270, when the dumbbell-shaped No. 8 specimens having 1 mm notch in a direction perpendicular to the direction of repeated tension at the center thereof are subjected to repeated tension at a frequency of 10 Hz under the conditions of 150 C., the number of repetitions until the specimen of the inner layer rubber fails is, in the range of 10% to 30% of the tensile strain applied, at least twice that of the side-reinforcing rubber, and in the reference condition, the ratio t2/t1 is 0.05 to 0.30.

A run-flat tire includes a carcass, a tire side portion and a side reinforcement layer. The carcass bridges between a pair of bead portions. The tire side portion links between a bead portion and a tread portion. A carcass maximum width position of the tire side portion, at which the width of the carcass is at a maximum, is provided at the tire radial direction outer side relative to a position that is at 40% of the tire section height. The side reinforcement layer is provided at the tire width direction inner side of the carcass. A thickness of the side reinforcement layer at the position that is at 40% of the tire section height is not more than 65% of a thickness of the side reinforcement layer at the carcass maximum width position.

The tire maximum width in the reference condition is the center value or more and the upper limit or less of the tire maximum width specified in the standard, and the tire maximum width position in the reference condition is located at the position, with a distance of more than 50% of the tire cross-sectional height, outward in the tire radial direction from the bead baseline.

A side reinforcing rubber layer includes a second rubber portion having a modulus constant between a boundary surface and a bead portion and larger than a first rubber portion arranged on a tread-portion-2 side. The boundary surface intersects outer and inner surfaces of the side reinforcing rubber layer at first and third points, respectively. The first and third points are arranged on the bead-portion side of second and fourth points, respectively, which are closest points to an outer end of a belt layer of the outer and inner surfaces, respectively. A distance between an inner end of the first rubber portion and the second point is larger than a distance between the second point and the first point.

The tire maximum width in the reference condition is the center value or more and the upper limit or less of the tire maximum width specified in the standard, and the tire maximum width position in the reference condition is located at the position, with a distance of more than 50% of the tire cross-sectional height, outward in the tire radial direction from the bead baseline.