A tire/wheel assembly, wherein a run-flat support body (3) comprising an annular shell (4) having an outer peripheral side as a support surface and an inner peripheral side formed in fork-shaped open legs and elastic rings (5) supporting the ends of the fork-shaped open legs on a rim is inserted into the hollow part of a pneumatic tire (2), and the height (A) of the run-flat support body (3) in the cross section thereof is 40 to 47% of the height (SH) of the pneumatic tire (2) in the cross section thereof.