Tread and sidewall construction for runflat tire

A pneumatic radial ply runflat tire having a tread, two inextensible annular beads, a carcass comprising a radial ply structure having at least one radial ply, a belt structure located between the tread and the radial ply structure, and two sidewalls reinforced by one or more inserts, the tire being characterized by:

• a tread having laterally outermost disposed tread ribs, each tread rib defining an outer contour;
• a sidewall rib disposed near a radially outermost region of each sidewall adapted for contact with a driving surface during runflat operation and free from contact with the driving surface during operation at normal inflation pressure, each sidewall rib defining an outer contour;
• circumferentially extending but circumferentially discontinuous first decoupling grooves disposed between each sidewall rib and each adjacent tread rib;
• and
• circumferentially extending second decoupling grooves disposed between the tread ribs and an adjacent central region of the tread the central region of the tread defining an outer contour.

A pneumatic radial ply runflat tire having a tread, two inextensible annular beads, a carcass comprising a radial ply structure having at least one radial ply, a belt structure located between the tread and the radial ply structure, and two sidewalls reinforced by one or more inserts, the tire being characterized by:

• a tread having a central region and adjacent laterally outermost disposed tread ribs;
• the central region of the tread defining an outer contour, and each tread rib defining an outer contour such that the laterally outermost disposed tread ribs are adapted for full contact with a driving surface during runflat operation but only partial contact with the driving surface during operation at normal inflation pressure;
• a sidewall rib disposed near a radially outermost region of each sidewall adapted for contact with the driving surface during runflat operation and free from contact with the driving surface during operation at normal inflation pressure, each sidewall rib defining an outer contour;
• circumferentially extending first decoupling grooves disposed between each sidewall rib and each adjacent tread rib;
• circumferentially extending second decoupling grooves disposed between the central region of the tread and an adjacent tread rib;
• wherein:
• a circular curve that defines the contour of each respective laterally outermost disposed tread rib and a circular curve that defines the contour of the central region of the tread intersect nontangentially at each respective second decoupling groove;
• and
• a circular curve defining the contour of a respective radially outermost disposed sidewall rib and a circular curve defining the contour of a respective laterally outermost disposed tread rib intersect nontangentially at each respective circumferentially disposed first decoupling groove.