Road
Road racing bikes are stiff, light and aerodynamic. The bicycle includes ultra-thin, high-pressure tires, which are light and offer minimal rolling resistance. Drop handlebars, which allow the cyclist to ride in a low tuck, ensure less wind resistance. Road-racing bikes have multiple gear combinations, allowing the cyclist to tackle a variety of conditions optimally. Time-trial bikes, a genre of road bikes, are for a single purpose: to cover a relatively short and flat distance in the least amount of time. To this end, the time trial bike features exceptionally low profile, extended handlebars and special wind-cheating components. The bikes most likely have carbon frames.
Off-road
With its weight and stiffness, the off-road racing bike's priority is handling the stress of traversing a dynamic, often undulating terrain. Mountain, BMX, Downhill, and Trials bikes fall under this category of racing bike. These bicycles feature wide, thick tires, special gearing, and sometimes shock absorbing forks and suspension. Common brake designs include traditional cantilever and hydraulic disc. While slightly heavier, bikers favor discs on these bikes for increased stopping power. Frames are either carbon or aluminum.
Cyclo-cross
A cyclo-cross racing bike is an almost perfect hybrid between a road and a mountain bike. The cyclo-cross racing bike resembles a road bike in design--lean, aerodynamic, low profile--but features many components inspired by off-road racing. A typical cyclo-cross race runs on both smooth and rough surfaces, ergo the hybrid design. Mid-size knobby tires provide both speed and traction. Cantilever brakes, which sit relatively high over the tire, offer easy maintenance and fouling by mud is unlikely. Two sets of brake-levers, incorporating both off-road and road designs, are on the bends and the flats of the handlebar. Frames most likely are lightweight and stiff aluminum.
Track
Sometimes called 'fixies', track bikes resemble road-racing bikes at first glance. The two bikes share the same aero profile, narrow wheels, and drop-style handlebars. Track bikes feature a single gear combination and fixed rear hub. Deeper hub flanges provide stiffer wheels, which allow for maximum acceleration during sprints. Ultra high-pressure tires provide low rolling resistance. Track bikes do not have brakes, forcing a rider to decrease speed gradually to stop. Professional track frames are usually either aluminum or carbon.
