The beads of a pneumatic tire having sidewalls of a cross-sectional shape, wherein upon inflation the midline thereof between the tread reinforcement and bead is convex with respect to the interior of the tire, are gripped by a rim having an annular channel generally elliptically shaped in cross-section and having its open side directed radially outwardly with respect to the axis of the wheel and inwardly directed annular flanges only partially closing the open side of the channel.