Patent ID: 7918256

Claim:
A heavy-duty tire comprising a tread portion, a pair of sidewall portions, a pair of bead portions, a carcass extending between the bead portions through the tread portion and sidewall portions, and a belt disposed radially outside the carcass in the tread portion, wherein when the tire is mounted on a standard wheel rim, inflated to a maximum pressure, and loaded with 100% of a maximum tire load, the tread portion has a ground contacting face which has: a circumferential length L97[W100] measured at a position P97[W100] spaced apart from the tire equator by an axial distance of 97% of one half of a ground contacting width TW[W100]; and a circumferential length L70[W100] measured at a position P70[W100] spaced apart from the tire equator by an axial distance of 70% of one half of the ground contacting width TW[W100], when the tire is mounted on the standard wheel rim, inflated to the maximum pressure, and loaded with 70% of the maximum tire load, the tread portion has a ground contacting face which has: a circumferential length L97[W70] measured at a position P97[W70] spaced apart from the tire equator by an axial distance of 97% of one half of a ground contacting width TW[W70]; and a circumferential length L70[W70] measured at a position P70[W70] spaced apart from the tire equator by an axial distance of 70% of one half of the ground contacting width TW[W70], and the circumferential lengths L70[W100], L97[W100], L70[W70] and L97[W70] satisfy the following conditions: 0.95 <L 70 [W 100]/L97 [W 100]<1.05; and 1.03 <L 70 [W 70]/L97 [W 70]<1.20, and in a 50%-pressure unloaded condition in which the tire is inflated to 50% of the maximum pressure and loaded with no tire load, a profile of the thickness center line of the carcass is provided in each shoulder region S with a single radius Rc of curvature of from 60 to 130 mm which is increased locally so that the radius Rc becomes decreased as the tire pressure increases to the maximum pressure, and the thickness center line in the 50%-pressure unloaded condition is positioned inside the thickness center line in a maximally-inflated unloaded condition in which the tire is inflated to the maximum pressure and loaded with no tire load, wherein the shoulder region S is positioned between an intersecting point X 1 of a widthwise center line of an axially outermost circumferential groove with the carcass, and a point X 2 positioned axially outwards of the intersecting point X 1 by a length of from 40 to 70 mm along the thickness center line of the carcass.