A racing bicycle, also known as a road bike, is a bicycle designed for competitive road cycling, a sport governed by according to the rules of the Union Cycliste Internationale (UCI). The UCI rules were altered in 1934 to exclude recumbent bicycles.
The most important characteristics about a racing bicycle are its weight and stiffness[citation needed] which determine the efficiency at which the power from a rider's pedal strokes can be transferred to the drive-train and subsequently to its wheels. To this effect racing bicycles may sacrifice comfort for speed. The drop handlebars are positioned lower than the saddle in order to put the rider in a more aerodynamic posture. The front and back wheels are close together so the bicycle has quick handling. The derailleur gear ratios are closely spaced so that the rider can pedal at their optimum cadence. Other racing bicycles, especially those used in time trialling, prioritize aerodynamics over comfort.
The UCI rules currently specify[8] that a racing bicycle have the following characteristics, :
be a vehicle with a front wheel steered by a handlebar and a rear wheel driven by a system comprising pedals and a chain by the legs moving in a circular movement
that the only points of support are the following: the feet on the pedals, the hands on the handlebars and the seat on the saddle
wheels must be of equal diameter, between 70 cm and 55 cm, and must have minimum 12 spokes; spokes can be round, flattened or oval, as far as no dimension of their sections exceeds 10 mm
maximum length 185 cm
maximum width 50 cm
the peak of the saddle must be at least 5 cm behind a vertical plane passing through the bottom bracket spindle
the saddle must be between 24 cm and 30 cm in length
the distance between the bottom bracket spindle and the ground must be between 24 cm and 30 cm
the distance between the vertical passing through the lower bracket spindle and the front wheel spindle must be between 54 cm and 65 cm
the distance between the vertical passing through the bottom bracket spindle and the rear wheel spindle must be between 35 cm and 50 cm
the maximum internal distance between the front fork ends is 10.5 cm, and of the rear stays 13.5 cm
minimum mass 6.8 kg (14.99 lb)
frame must be built around a main triangle, constructed of tubular elements (that may have non-circular cross-sections) such that the form of each encloses a straight line
The maximum height of the frame elements shall be 8 cm and the minimum thickness 2.5 cm. The minimum thickness shall be reduced to 1 cm for the chain stays and the seat stays. The minimum thickness of the elements of the front fork shall be 1 cm; these may be straight or curved. The top tube may slope, provided that this element fits within a horizontal template defined by a maximum height of 16 cm and a minimum thickness of 2.5 cm
Note that the regulations regarding the dimensions of the bike are allowed exception, given that the rider can demonstrate a morphological need for the exception based on limb size or other factors.
These rules effectively and purposely rule out recumbent bicycles, and have done so since 1934.
