Bicycle frame

A bicycle frame is the main component of a bicycle, onto which wheels are fitted. It consists of a head tube, top tube, down tube, seat tube, seat stay and chain stay.

The most common frame design is the diamond or double triangle, pictured above. Touring frames tend to be longer, while racing frames are more compact. There are variations on this design, especially on mountain bikes, which require a greater flexibility to absorb shocks from the rough road.

Bike frame materials include:

1. Aluminum - Very lightweight, but inflexible. If too much flexion is demanded of aluminum, it will fail, i.e. the tube will crack.
2. Steel - Flexible, strong but relatively heavy, it is the most common material used in building frames.
3. Titanium - Lightweight, flexible, strong. Seems like the perfect material. It is 15 times more expensive than steel, making these frames out of reach of most cyclists.
4. Carbon fiber - newcomer, has promise, especially since the fibers can be oriented in such a way as to optimally absordb the anticipated stress. The difficulty is predicting where a stress might be.