Patent ID: 7740037

Claim:
A runflat tire comprising a toroidal carcass which extends from a tread portion to each of bead cores in bead portions through sidewall portions, and a pair of sidewall-reinforcing rubber layers which are disposed axially inward of the carcass in the sidewall portions and which have an approximately crescent-shaped cross section, wherein each of the sidewall-reinforcing rubber layers comprises a radially outermost first rubber portion, a second rubber portion which is contiguous to the first rubber portion and extends therefrom toward the bead portion, a third rubber portion which is contiguous to the second rubber portion to substantially locate radially inward of the second rubber portion, and a fourth rubber portion which is contiguous to the third rubber portion to substantially locate radially inward of the third rubber portion, the second rubber portion has a complex modulus E* 2 of at least 1.1 times the complex modulus E* 1 of the first rubber portion, the third rubber portion has a complex modulus E* 3 larger than the complex modulus E* 2 of the second rubber portion, and the fourth rubber portion has a complex modulus E* 4 larger than the complex modulus E* 3 of the third rubber portion, in a meridian section of the tire including the rotational axis of the tire in a normal state that the tire is mounted on a standard rim and inflated to a normal internal pressure but is unloaded, the interface between the first rubber portion and second rubber portion, the interface between the second rubber portion and third rubber portion and the interface between the third rubber portion and fourth rubber portion lie substantially at right angles to the center line of the thickness of the sidewall-reinforcing rubber layer, when measured along the center line of the thickness of the sidewall-reinforcing rubber layer, the length Sa of the first rubber portion 9 a is at least 25% but at most 50% of the full length S of said center line, and the length Sb of the second rubber portion is larger than the length Sc of the third rubber portion which is larger than the length Sd of the fourth rubber portion.