A racing bicycle, also known as a road bike, is a bike which has been 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 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 his or her optimum cadence. Other racing bicycles, especially those used in time trialling prioritize aerodynamics over comfort.
Bicycles for racing on velodromes are track bicycles; bicycles for racing offroad are mountain bicycles, cyclo-cross bicycles or cycle speedway bicycles; bicycles that race according to the rules of the International Human Powered Vehicle Association include faired recumbent bicycles which, on flat ground, are the fastest bicycles in the world.
Time trial bicycles are a subset of racing bicycles that are designed for time trial events. The UCI rules for these bikes are slightly less prescriptive than those for “massed start road races”.
Triathlon bicycles are governed by International Triathlon Union (ITU) rules, which allow more recent technological developments than do the UCI rules.
Race bike components are collectively referred to as the groupset. The quality of the groupset determines how refined the bike feels, how much maintenance it requires, and contributes to the performance of the bike. The three major groupset manufacturers of complete groupsets for racing bicycles are Shimano, SRAM, and Campagnolo. Some companies only produce specific components of the groupset, such as Full Speed Ahead (often abbreviated to FSA). The companies have different design philosophies, and some cyclists have great brand loyalty for one or the other.