Racing bicycles are designed differently than your standard bike and instead, the design adheres to the rules of the Union Cyclist International or UCI. In 1934, UCI rules were altered and excluded the recumbent type bikes.
Racing bicycles are extremely light weight and aerodynamic efficient and provide maximum ergonomic design to accommodate the rider.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.
Racing wheels will greatly affect the overall performance of a racing bike. The rim of the wheel can be shaped for greater aerodynamic efficiency making a triangular cross-section to form a teardrop with the tire. For hill climbs, however, energy losses due to the higher rotating weight of most aerodynamic rims are greater than the aerodynamic drag reduction that they offer, so a traditional lighter box-sectioned rim is often used.
For aerodynamics and rotating weight, it is generally better to reduce the number of spokes in the wheel. For high-end wheel sets, the spokes can be shaped to have a bladed cross-section, further reducing wind resistance.
Wheel rims use aluminum alloy as the most common material for it's durability and more importantly light weight. Using a molded carbon fiber rim reduces weight compared to a metal rim. Using exotic materials, race-grade wheel sets are very expensive. Riders who race often choose to own at least two pairs of wheels: a heavier, more durable, and cheaper wheel set for training, and a lighter, more aerodynamic wheel set for racing.
To reduce both air resistance and rolling resistance on the road, tires are lightweight, narrow, and have a thin, smooth tread. They are inflated to a high pressure, typically around 8 bar (820kPa/120psi); track racing tires can be inflated up to c.14 bar. Until recently, most racing bikes used "tubular/single/sew-up" tires which have no beads: they are sewn around the tube and glued to the rim. These tires provide an advantage in weight (lacking the relatively heavy wire bead), rolling resistance, grip and pinch flat protection, but their greatest advantage lies in the ability to use a very lightweight simple box-section rim, rather than the U-shaped clincher rim. A U-shaped clincher rim must use relatively heavier gauge to prevent the tire pressure from spreading the inherently weak U shape and allowing the tire to come off the rim. Advances in tire technology, however, have seen the far more practical (due to greater ease of changeability) clincher (beaded) tire close the gap.
Some manufacturers create Tubular-Clincher tires, where the tires are sewn around the tubes and have a bead, but there is some debate as to the effectiveness of a tubular-clincher tire. Proponents believe that it has all the advantages of a tubular tire made to fit a clincher rim, but critics argue that the design includes disadvantages inherent to both systems---the rim weight is still high, the tire is more expensive than a standard clincher tire, and repairing a puncture on a tubular clincher is as inconvenient as it is with a standard tubular tire. However, a particular benefit of the tubular-clincher design is that the risk of pinch flats is very low (like the tubular tire), yet it allows the use of the more popular clincher wheel.