Run flat system having a spring suspension

A run flat device configured to be fitted to a tubeless mounted assembly for a motor vehicle, which includes a wheel rim and a tire cover including beads mounted against edges of the rim, the run flat device including: an annular supporting structure which is configured to be mounted around the rim so as to support the cover following a drop in inflating pressure inside the mounted assembly, including: three composite spring segments forming sectors in an arc of a circle assembled circumferentially around the rim forming the annular supporting structure by means of transverse pins whose shape geometry is asymmetrical; and an arrangement for locking the beads against the edges which are configured to connect the annular supporting structure to these beads.