An assembly comprising a wheel rim and an annular safety support member mounted on the rim portion between the rim bead seats and extending radially outwards beyond the rim bead retaining flanges to support a tire mounted on the rim when in a deflated condition. The support member rotates with the rim in the non load-bearing condition but rotates relative to the rim in the load-bearing condition to compensate for circumferential differences between the tire tread and the radially outer surface of the support member. The confronting surfaces on the support member and rim portion are profiled to axially locate the support member on the rim. Preferably the radially inner surface of the support member is of shallow convex profile and the confronting surface on the rim portion is of shallow concave profile.