A track
frame is specific to its intended use, with emphasis on rigidity and lightness. Frames for sprinting seek to maximize rigidity, while those for general racing seek to reduce aerodynamic drag. The
dropouts or
track ends face rearwards to facilitate chain tension adjustment. A true track fork, unless aerodynamics are the primary consideration, has round-section blades for greater lateral stiffness when sprinting. The crown is sometimes drilled to give the option of mounting a front brake when the bike is used on the road.
Rules The governing body, the
Union Cycliste Internationale (UCI), sets limits on design and dimensions as well as the shape and diameter of the tubes used to construct the frame. The UCI permits special exceptions for the construction and geometry of track bikes. A
Keirin bike is a track bike for Keirin races in Japan that meets the strict system of standards of the
JKA Foundation (Japan Keirin Autorace Foundation), the governing body for Keirin competitions, still popular under the abbreviation of its predecessor body - NJS (Nihon Jitensha Shinkōkai or the Japanese Bicycle Association).
Geometry A track bicycle frameset typically differs from one used on the road in the following ways: • higher
bottom bracket – so the pedals are less likely to strike a steeply banked track • shorter chainstays and overall wheelbase – befitting the tight quarters of velodrome races • steeper
seat tube angle and longer reach – trading long-term comfort for aerodynamic benefits • steeper head tube angles and lower fork offset to achieve higher
trail and lower
flop – for stability at speed near other riders These changes represent substantial compromises compared to a typical road bike. For example, even medium-sized track frames often have substantial toe overlap with the front wheel; while not an issue for velodrome riding, it can make slow-speed turns difficult if the bike were used on the road.
Material Frames are assembled from tubular elements (typically with round or elliptical cross sections), or cast in a mould for "one-piece" type models. The most popular materials for frame building include
steel,
aluminium, or
titanium alloys,
carbon fiber, or a combination of these materials. Carbon fiber frames are most common at the professional level. ==Gear ratio==