Bicycles & Frames

A bicycle frame is the main component of a bicycle, onto which wheels and other components are fitted. The modern and most common frame design for an upright bicycle is based on the safety bicycle, and consists of two triangles, a main triangle and a paired rear triangle. more...

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This is known as the diamond frame, and this article is about them. For other styles of bicycle frames, see the step-through, mixte, Humber bicycle, and recumbent bicycle articles.

In the diamond frame, the main triangle consists of the head tube, top tube, down tube and seat tube. The rear triangle consists of the seat tube, and paired chain stays and seat stays. The head tube contains the headset, the interface with the fork. The top tube connects the head tube to the seat tube at the top, and the down tube connects the head tube to the bottom bracket shell. The rear triangle connects to the rear dropouts, where the rear wheel is attached. It consists of the seat tube and paired chain stays and seat stays. The chain stays run parallel to the chain, connecting the bottom bracket to the rear dropouts. The seat stays connect the top of the seat tube (often at or near the same point as the top tube) to the rear dropouts.

Frame tubes

The diamond frame consists of two triangles, a main triangle and a paired rear triangle. The main triangle consists of the head tube, top tube, down tube and seat tube. The rear triangle consists of the seat tube, and paired chain stays and seat stays.

Head tube

The head tube contains the headset, the interface with the fork. In an integrated threadless headset, the bearings interface directly with the metal surface on the inside of the head tube

Top tube

The top tube (popularly referred to as the crossbar) connects the top of the head tube to the top of the seat tube. In a traditional-geometry racing bicycle frame, the top tube is horizontal. In a compact-geometry frame, the top tube is sloped downward toward the seat tube. In a mountain bike frame, the top tube is almost always sloped downward toward the seat tube. See Road and triathlon bicycles for more information on geometries.

Control cables are routed along mounts on the top tube, or sometimes inside the top tube. Most commonly, this includes the cable for the rear brake, but some mountain bikes and hybrid bicycles also route the front and rear derailleur cables along the top tube.

The space between the top tube and the rider's groin while straddling the bike and standing on the ground is called clearance. The total height from the ground to this point is called the height lever.

Down tube

The down tube connects the head tube to the bottom bracket shell. On racing bicycles and some mountain and hybrid bikes, the derailleur cables run along the down tube, or inside the down tube. On older racing bicycles, the shift levers were mounted on the down tube. On newer ones, they are integrated with the brake levers on the handlebars.

Read more at Wikipedia.org