Track bicycle
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A track bicycle or track bike is a bicycle designed for racing at a velodrome. Unlike road bicycles, they have a single gear, no freewheel, and no brakes . Tires are narrow and at high pressure to reduce rolling resistance. Tubular tires are often used.
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[edit] Frame design
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- See also: Bicycle frame
A track frame is specific to its use. Rigidity is more important than lightness. Frames for sprinting are as rigid as possible, those for general racing as aerodynamic as possible.
[edit] Rules
The governing body, the International Cycling Union (UCI), sets limits on design and dimensions as well as the shape and diameter of the tubes used to construct the frame.
[edit] Geometry
A track bicycle differs from one used on the road by having:
- higher bottom bracket so the pedals don't touch a steeply banked track
- steeper seat tube for a more aerodynamic position,
- steeper head tube for more responsive steering,
- less fork rake
Typical track frames use 120mm spacing for the rear hub. The dropouts face backwards to help adjust chain tension.
[edit] Material
Frames can be made of steel, aluminium, carbon fiber, or titanium. Carbon fiber is most common at the professional level.
[edit] Gears
Track bicycles have only one gear so its size is important. A lower gear allows quicker acceleration or 'jump.' But a bigger gear makes sustain speed easier, important in pursuit, time trial and bunched races such as points or scratch events. Without a good jump, the rider risks opponents accelerating away; without good sustained speed, he will be unable to keep up with a fast race. Track cyclists practice fast pedalling as a compromise.
Long-distance attempts such as the hour record use high gear combinations such as 52x12 or 55x14. Ondřej Sosenka used 54x13 with 190mm cranks to set the 2005 record.
[edit] Chain
There are two common widths of single speed and fixed gear bicycle chains: 1/8 inch and 3/32 inch. The chainring, sprocket and chain should all be the same width. Although an 1/8-inch chain will work on a 3/32-inch chainring or sprocket, it is not ideal. A 3/32-inch chain will not work on a 1/8-inch chainring or sprocket. Because they do not need to shift from sprocket to sprocket, track chains use a full bushing to allow little flex and to be stronger. All bicycles with derailleur gears use bushingless chains which flex, making gear changing possible.
