A polyurethane-polymer composition suitable for preparing a lightweight tire support includes at least one isocyanate, at least one polyol, and at least one chain extender. A polyurethane-polymer composition can also include an additive such as a catalyst, a filler, a surfactant, a colorant, and a mold-release agent. A lightweight tire support can be prepared from a polyurethane-polymer composition by, for example, reaction injection molding. Such a tire support desirably has temperature stability and load-bearing capability.