Racing bicycle

From Academic Kids

An aluminum racing bicycle made by  and built using  components.  It uses a semi-aerodynamic wheelset with low spoke count.
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An aluminum racing bicycle made by Raleigh and built using Shimano components. It uses a semi-aerodynamic wheelset with low spoke count.

A racing bicycle is a bicycle designed for road cycling according to the rules of the Union Cycliste Internationale (UCI). (Bicycles for racing indoors are track bicycles; bicycles for racing offroad are mountain bicycles or cyclo-cross bicycles; bicycles that race according to the rules of the International Human Powered Vehicle Association are recumbent bicycles.)

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Kusuma_bike_large.jpg
A racing bicycle made by Cyfac using shaped aluminum and dual carbon fiber chain- and seat-stays. It uses Campagnolo components.

The two most important things about a racing bicycle are its weight and the aerodynamic efficiency of the rider's position. Drop handlebars and optional handlebar extensions are combined with a raised seat in order to put the rider in a more aerodynamic posture. The front and back wheels are close together so the bicycle can turn very quickly. The derailleur gear ratios are closely-spaced so that the rider can pedal at his or her optimum cadence.

The wheelset greatly affects the performance of a racing bike. The wheels rotate at high speeds; consequently their moment of inertia matters a lot. 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 hillclimbs, however, effects from weight overcome those from aerodynamics, and the traditional 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 wheelsets, the spokes can be shaped to have a bladed cross-section, further reducing wind resistance.

The most common material for a wheel rim is aluminum alloy. Using a molded carbon fiber rim reduces weight compared to a metal rim. Using exotic materials, race-grade wheelsets are very expensive. Riders may choose to switch to cheaper and heavier wheels for training; some of the lightest wheelsets are relatively fragile.

To reduce both air resistance and friction on the road, tires are thin and smooth, and inflated to high pressure, typically around 120PSI / 820kPa. 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 both rolling resistance and grip, but advances in tire technology have seen the far more practical clincher (beaded) tire close the gap.

Race bike componentry (excluding frameset, wheelset, bars & stem, pedals, seat and seatpost) is 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 two major groupset manufacturers for racing bicycles are Shimano and Campagnolo. The companies have different design philosophies, and some cyclists have great brand loyalty for one or the other.

In the early 1990s, Shimano introduced STI dual control: combined brake/shift levers, or "brifters". Previously, the shifters were mounted on the stem or the down tube of the frame. Dual control addressed the problem of having to reposition a hand to change gears. STI was followed by the competing Campagnolo/Sachs Ergolever. Other than this, the general design of a racing bicycle has changed little since the development of derailleur gears.

For recreational cycling, the racing bicycle is less popular than the mountain bike. Mountain bikes, through mass production and popularity, are less expensive. A new entry-level mountain bike starts around half the price of an entry-level racing bike.

It is thought that racing bikes are less durable and less strong than mountain bikes, making them less suitable for everyday use. However, cyclo-cross bikes, which are ridden off-road, are closer to racing bikes than to mountain bikes. They have wider, treaded tires and cantilever brakes instead of caliper brakes.

The UCI specifies [1] (http://www.uci.ch/modello2.asp?1stLevelID=C&level1=1&level2=14&idnews=2443) 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
  • wheels must be of equal diameter, between 70 cm and 55 cm, and must have minimum 12 spokes
  • 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 weight 6.8 kg
  • 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

See also

nl:Racefiets

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