The present invention relates to a wheelchair for negotiating obstacles comprising a chair, a pair of rear wheels, a pair of caster wheels, and characterized by a pair of pivot leg assemblies, each independently located to the fore of the pair of caster wheels and comprising a pivot handle; an auxiliary caster wheel; a threaded rod connecting the pivot handle and the auxiliary caster wheel; a nut for fastening the threaded rod in position; wherein the auxiliary caster wheel can be extended and retracted by rotating the pivot handle.