This depends on the bike. If you have a commuter or typical front-suspension or hard front/tail mountain bike, then you can change it from the default treads to road treads. However, you most likely can't change their wheel to a road bike wheel because 1) the wheel size for a road bike is often larger than the mountain bike/commuter size and 2) your commuter and mountain bike often does not have the same wheel hub width as a road bike does.