A safety or emergency insert device positioned on a wheel rim inside a tire chamber to support the tire in a deflated condition. The device has an annular ring member of substantially C-shaped cross section which member has a rim-engaging portion, an axially extending tire tread support portion and a curved intermediate portion joining the rim-engaging portion with one lateral edge of the tire tread support portion. The tread support portion is radially deflectable when a radial load is applied thereto by the weight of a vehicle when the tire surrounding the device is deflated. The annular ring member is made preferably of resilient plastic, spring steel or other suitable resilient material which will provide deflection when the support device is supporting a vehicle running on a flat tire.