A track bicycle or track bike is a bicycle optimized for racing at a velodrome or outdoor track. Unlike road bicycles, the track bike is a fixed-gear bicycle and so has a single gear and neither freewheel nor brakes. Tires are narrow and inflated to high pressure to reduce rolling resistance. Tubular tires are often used.
Template:Seealso A track frame is specific to its use. Rigidity is more important than lightness. Frames for sprinting are as rigid as possible, while those for general racing as aerodynamic as possible.
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.
A track bicycle differs from one used on the road by having:
- higher bottom bracket so the pedals do not touch a steeply banked track
- steeper seat tube for a more powerful aerodynamic position,
- steeper head tube for more responsive steering,
- less fork rake.
Typical track frames use 120mm spacing for the rear hub. The dropouts or track ends face rearwards to facilitate chain tension adjustment with very tight clearances in front of the rear tire that would prevent wheel removal with forward facing dropouts.
Track bicycles have only one gear so its size is important. A lower gear allows quicker acceleration or 'jump.' But a bigger gear makes sustained 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 (cadence) as a compromise.
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.de:Bahnrad it:Bicicletta da pista he:אופני מסלול nl:Baanfiets ja:トラックレーサー pl:Rower torowy sl:Dirkalno kolo