A wheel with a self-contained drive mechanism is provided to propel (or assist in propulsion of) bicycles, tricycles, and similar vehicles. The wheel preferably takes the form of a shock absorbing detachable wheel, which is readily received within the dropouts of a bicycle frame or fork to be attached therein by a standard quick-release mechanism. Thus, the wheel may be added to (or removed from) preexisting standard bicycles and the like.