A run-flat device (13) for fitting on the outer circumference of a wheel (11) inside an inflatable tyre (12). The device (13) comprising an annular ring (14) made up of a plurality (preferably three) of arcuate segments (15) interconnected at each end by clamping means (23, 23a, 23b, 28, 29, 35) equally spaced around the ring that imparts to each segment (15) a circumferential clamping force and an axial clamping force to urge the segments circumferentially and axially towards each other.