A wheel assembly includes a collapsible wheel and an airless flexible tire mounted on the wheel. The wheel includes a central portion and a plurality of circumferentially spaced mounting elements attached to the central portion. Each of the mounting elements is movable between a retracted position and an extended position, and may be pivotally attached to the central portion of the wheel and configured to pivot between the retracted position and the extended position. The tire may be positioned on the wheel when one or more of the mounting elements is in the retracted position, and the one or more mounting elements are moved to the extended position wherein the mounting elements engage and support the tire.