A pneumatic tire

Claim 1

A pneumatic passenger radial tire comprising a ground-engaging tread portion having a pair of lateral edges, a pair of sidewall portions each of said sidewall portions extending from one of said lateral edges respectively radially inwardly of and toward the rotational axis of the tire and terminate in a bead portion, an inextensible bead core disposed in each of said bead portions, a carcass reinforcing ply structure extending through said sidewalls and tread portion and at each end being wrapped about one of said bead cores, said carcass reinforcing ply structure consisting of a single ply layer, a tread reinforcing ply structure disposed radially outwardly of said carcass reinforcing ply structure and beneath said ground-engaging tread portion, characterized by said carcass reinforcing ply structure when said tire is mounted on a rim for which it was designed and inflated to design inflation pressure following the natural equilibrium curve from a point substantially axially adjacent the radially outermost point where said tire meets said rim and radially outwardly to the point substantially adjacent the lateral ends of said tread reinforcing structure, each of said bead portions being provided with a hard rubber apex. disposed radially outwardly of said bead core between said carcass ply structure and said end of said carcass reinforcing pl y structure, said apex having a radially outer end which terminates at a point spaced from the nominal rim diameter a distance no greater than 20% of the maximum carcass section height, a rubber chafer disposed axially outwardly of said ends of said carcass reinforcing ply structure, the radially outer end of said chafer terminating at a point spaced from the nominal rim diameter a distance no greater than about 35% of the maximum carcass section height, the radially outer end of each of said ends of said carcass reinforcing ply structure being spaced from the nominal rim diameter a distance no greater than approximately 20% of the maximum carcass section height and being disposed closely adjacent the carcass reinforcing ply structure, each of said sidewall portions being provided with a flex zone the radially innermost portion of which is spaced from the nominal rim diameter a distance approximately equal to 20 to 30% of said carcass maximum section height, said flex zone extending radially outwardly with respect to the axis of rotation of said tire a distance of at least 40% of the carcass section height, said flex zone comprising a central primary flex zone and a pair of secondary flex zones, one disposed adjacent each radial end of said primary flex zone, said sidewall in said primary flex zone having a substantially constant cross-sectional width no greater than about .17 inches (4.31 mm), said sidewall in said secondary flex zones having a cross-sectional width equal to or no greater than about .22 inches (5.58 mm) of the cross-sectional width of said sidewall in said primary flex zone.