The invention provides a runflat device for a motor vehicle, the device comprising a ring for mounting inside a tire on a one-piece non-standard wheel rim that presents a drop center, an inner flange and an outer flange, said ring being made as at least two sectors each having a radially inner zone and a radially outer zone, wherein the sectors of the ring are independent of one another, and wherein each sector is fixed to the rim via its radially inner zone.