Land-vehicle Design

A bicycle is designed as a bicycle-frame only, by a an established brand (e.g. Diamond, Step-through, Cantilever frame types).

All other components that go into a finished bicycle are designed by specialised component manufacturers, such as

wheels and tires, 

gear-shifting mechanisms, 

brakes,

drivetrain components such as chain-cranks, chains and freewheels,

and shock-absorption systems.

Usage classes are based on terrain, targeted speed, loading level etc.

Of late, DC-motor based drivetrain assist systems have gained market-traction.