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Frame
From WikiPedalia
The skeleton of a bicycle. The most common type of frame is called the "diamond" frame, and consists of two (of three, depending on how you look at it) triangles.
- The front triangle consists of the seat tube, the top tube, and the down tube...well, it also includes the head tube, so is is not a perfect triangle, but the head tube is usually fairly short, so it is pretty close to being a triangle. The front triangle holds the saddle, the bottom bracket, and, via the headset, the front fork.
- The rear triangle (or triangles, if you count both sides separately) includes the seat tube, seat stays and chain stays.
The diamond frame has evolved over the course of more than a century, and every dimension has been tinkered with and fine-tuned to the point that it is a nearly perfect design for the tubular materials commonly used.
This is not to say that it is the ultimate, however. For some applications, the cross frame is still viable, and for moldable materials, monocoque designs may yet eclipse the diamond. It is also not at all clear that the diamond design lends itself to suspension applications.
