Wheels
The wheels of a bike are compound systems that must carry out a number of functions. The hub connects the wheel to the bike, and at the rear delivers the forces from the pedals. Spokes connect the hub to the rim. Spokes may be either in either tension or compression depending on the wheel design (see the three pictures below). The rim caries the tires and frequently transfers braking forces to the wheel. The tires make contact with the ground and have a tread pattern and structure that is determined by the type of bike.