A tricycle convertible to a bicycle. The tricycle has a first wheel rotatably mounted on one end portion of a frame, and a pair of laterally spaced wheels rotatably mounted on a second end portion of the frame, wherein the laterally spaced wheels are movable, while the tricycle is in motion, between a first position with relatively wide ground-level spacing and a second position with minimal ground-level spacing. A wheel hub capable of providing adjustable wheel camber has left and right pivotally mounted axles extending laterally from the hub body, the axles each adapted to support a wheel and mounted so as to pivot vertically, and a dual camber control mechanism coupled to the axles and adapted to provide coordinated camber adjustment in the same direction for wheels on both axles. The hub has sufficient range of motion to allow the wheels to change from negative camber to positive camber, and is useful in a method of stabilizing a bicycle or the like to increase safety during rider training. The method involves a tricycle mode of operation in which the laterally spaced wheels have negative camber, and a bicycle mode of operation in which the laterally spaced wheels have positive camber, with a change from tricycle mode to bicycle mode while in motion, whereby a rider in training may start moving with stable three-point ground contact and, when in motion and balanced, effectively start riding a bicycle.