Tread stiffening for two ply runflat tire

A pneumatic radial two-ply runflat tire having a tread, two inextensible annular beads, two sidewalls, an inner liner, a belt structure located between the tread and a carcass, the latter comprising a radial ply structure consisting of a first radial ply and a second radial ply that are separated in each sidewall by respective axially outermost sidewall wedge inserts, and a second set of axially inward disposed sidewall wedge inserts disposed between the inner liner and the first ply, the tire being characterized by:

• the first ply being reinforced with a nonmetallic material having a tensile modulus of elasticity of between about 4 GPa and about 30 GPa, and a specific gravity in the range of between about 1 and about 3;
• the second ply being reinforced with an aramid material having a tensile modulus of elasticity in the range of between about 20 GPa and about 80 GPa;
• the second ply being prestressed in tension such that the second ply has a greater modulus of elasticity than the first ply;
• and
• the first ply being a floating ply but the second ply being clamped around the respective beads such that turnup ends of the second ply are located radially outward of the beads.