A pneumatic radial ply passenger tire (10) having a tread (12), a casing with two sidewalls (20), two radial plies (38, 40) extending from and wrapped about two annular beads (26) and a belt reinforcement structure (36) located radially between the tread and the plies. Inner ply (38) is reinforced with essentially inextensible metal cords and is designed to carry a compressive load during runflat operation. Outer ply (40) is reinforced with organic-fiber cords designed to withstand tensile stresses during runflat operation. A circumferentially deployed insert (42) is disposed between the inner and outer radial plies (38, 40) in each sidewall (20) adjacent to the shoulder of the tread. The metal cords (41) of inner ply (38) have compressive-load-hearing capacity which reduces the mass of the insert material (42). The metal cords (41) also have thermal conductivity properties that dissipate heat buildup from both ply (38) and insert (42).