Track

Track bicycles are very specifically designed as track racing conditions are very tightly regulated, the rear dropouts only have to accommodate a single fixed sprocket, meaning dropout width is a standard 120mm. The bottom bracket is a little higher to allow adequate pedal clearance when on the banking of the velodrome. Brakes are not allowed for track racing, as such the clearances can be kept to the bare minimum and as there is no risk of anything getting jammed then the closer the clearance the better. Gears are not allowed on track bikes so there is no provision for anything relating to gears.