Motor scooters are in many cases, classified as a separate vehicle to motorbikes, given their large amount of differences, and different evolution. Scooter engine sizes range smaller than motorcycles, , and have all-enclosing bodywork that makes them cleaner and quieter than motorcycles, as well as having more built-in storage space. Modern scooters have automatic clutches and continuously variable transmissions (CVT), which makes them easier to learn on and to ride. Scooters usually have smaller wheels than motorcycles. They usually have the engine as part of the swingarm, so that their engines travel up and down with the suspension.