Run-flat tire

A run-flat radial tire including:

• a tread portion;
• a pair of side wall portions extending internally in the radial direction from both end portions of the tread portion;
• a bead portion extending continuously on an interior circumferential side of each of the side wall portions;
• a tread rubber provided to the tread portion and forming a road contacting surface;
• a radial carcass formed by one or more carcass plies, side portions of which carcass plies are turned-up outwards in the radial direction around a pair of bead cores disposed to each of the bead portions;
• a belt formed by one or more belt plies disposed between the radial carcass and the tread rubber;
• and,
• a reinforcing rubber layer having a substantially-crescent-shaped cross section and disposed on the inner side in the tire width direction of the radial carcass at at least a portion corresponding to each of the side wall portions,
• wherein the tread portion has a rigidity reducing portion that reduces the rigidity of the tire, the rigidity reducing portion being formed in an area located on the inner side than an end of the belt in the tire width direction and on the outer side than a road-contacting end in the tire width direction at a 75% load.