Runflat supporting ring for vehicle and tire/wheel assembly including it

The tyre, for use on a motor vehicle wheel with a rim (10) in two or more sections (10a, 10b), has an inner ring (32) to support it when partially or completely deflated, and reinforced rubber clamps (36) to hold the tyre beads (21, 22) against the inner edges of the rim. The ring is in sectors with rigid aluminium- or titanium-based metal or composition walls (33) containing at least one inner volume (34) that can be filled with a cellular material.