Single-speed bicycle

ing or other methods for varying the gear ratio of the bicycle. Historically, all bicycles were single speed bicycles, specifically fixed-gear or fixed wheel single speed bicycles that had no mechanism to vary the gear ratio or to allow the pedals to coast while the drive wheel moved.

Many individuals looking to improve the efficiency, speed and comfort for bicycle riders developed freewheel systems and gearing systems for bicycles. The term 'single speed' in this article refers to modern bicycles.

There are many types of modern single speed bicycles; BMX bicycles, most bicycles designed for children, cruiser type bicycles, classic commuter bicycles, unicycles, bicycles designed for track racing, fixed gear road bicycles, and fixed gear mountain bicycles.

A subset of single speed bike is the fixed-gear bicycle. The difference is that a fixed-gear bike does not have freewheel mechanism to allow coasting.

Advantages and disadvantages versus multi-speed bicycles

Advantages

A single-speed bicycle is generally cheaper, lighter, and mechanically simpler than its multi-geared equivalent. Without derailleurs or other gearing systems, there are fewer parts on the bicycle that require maintenance. Replacing gears and chains on a single-speed bicycle is significantly cheaper. This is particularly advantageous when biking in muddy and gritty conditions which would wear out the expensive components of a geared bike.

The drivetrain efficiency of a single-speed can be greater than today's typical multi-geared bicycles. A straight chainline, lack of chain drag from rear derailleur jockey pulleys, and lack of chainrings, ramps and pins all improve efficiency. As a single rear cog takes less space than the typical seven to ten cogs present on most multi-geared rear cassettes, rear wheels can be built with little or no dish, which is inherently stronger.

Single-speed bicycles are characterized by a simple and uncluttered look.

Disadvantages

* smaller range of efficient speeds at which the bicycle can be pedaled
* typically lower top speed of bicycle
* banned from some races and other bicycle eventsFact|date=May 2008

Types of single speed bicycles

While track-racing bicycles are always single speed, mountain bicycles, road bicycles, cyclo-cross bicycles, and hybrid bicycles can be made as or changed into a single speed. Mountain bike single speeds designed for trail riding often have a relatively low, or easy and slow, gear ratio. This allows them to climb hills and deal with obstacles and gradients better. Single speed bicycles designed for road riding typically have higher, or harder and faster, gear ratios.

Single speed bicycles and fixed gear bicycles are popular with bicycle messengers for their reliability and durability. Depending on the situation, a messenger may prefer a mountain bike based single-speed, which can be an urban tank, able to roll over almost any obstacle, or a road bike-based single-speed, which is fast and light.

Statements by cycling industry representatives and journalists fueled the perception that major bicycle manufacturers discouraged modern single speed bicycles. However, increased popularity of the single speed has resulted in the design, marketing, and production of many models. In the United States market, bicycle companies Bianchi, Cannondale, KHS, Kona, Raleigh, Giant, Specialized, and Trek all have recently produced and marketed single speed bicycles.

Single speed mountain bikes are typically constructed with no suspension (fully rigid) or front suspension forks. However, as single speed bicycle production by major manufacturers has become more common, a limited number of fully suspended single speed mountain bikes have been produced. However the popularity of "full-suspension" single speeds has been limited by the general impression that the increased weight and complexity of a fully suspended frame runs counter to the "light and simple" image sought by many single speed riders.

Chain tensioning

Single-speed bicycle builders have devised a variety of methods for producing and maintaining the proper chain tension. The most common method is horizontal rear dropouts or track ends. These allow the rear wheel to be moved fore or aft as necessary. Another method uses an eccentric mechanism either in the bottom bracketcite web
url = http://www.philwood.com/Eccentric%20Shell.htm
title = Bottom Bracket Eccentrics & Shells
accessdate = 2007-10-19] or in the rear hub.cite web
url = http://www.sheldonbrown.com/harris/white-hubs.html
title = The White Industries ENO Single Speed Fixed/Free Hubs
accessdate = 2007-10-19] If neither of these are an option, when working with an existing frame not originally designed for single-speed use for example, some kind of idler pulley, such as the Surly Singlelatorcite web
url = http://www.surlybikes.com/parts/singleator_pop.html
title = Singlelator
accessdate = 2007-10-19] , can be used to take up chain slack. Finally a magic combination of chainring, cog, and chain length may work well enough until the chain wears.

Throughout the years bicycle designers have produced belt driven bicycles.Fact|date=July 2008 While these belts cannot be shifted between gears like a chain, they offer singlespeed or hub geared drivetrains with improved increased wear resistance, quieter operation, and lubrication-free cleanliness. Belts also do not change length during their lifespan in the same way that chains "stretch" or increase in pitch as their link pivots wear. This keeps the pitch of the belt's teeth constant and dramatically decreases wear on gear teeth. Belts have failed to over take chains in popularity for bicycles because they have historically been less efficient.Fact|date=July 2008 Also replacement of the one-piece belt requires traditional diamond bicycle frames to have a special split chainstay.

References

ee also

* Single Speed World Championship
* Cruiser bicycle

External links

* [http://www.trackcyclingsa.co.za/Downloads/Gearratiocalculator/tabid/263/Default.aspx TrackCyclingSA - gear ratio calculator]
* [http://www.singlespeedbleed.com Singlespeedbleed.com]
* [http://www.singlespeed.net/ Singlespeed.net]
* [http://www.sswc07.com/ 2007 Single-speed World Championship Race]
* [http://www.fixedgeargallery.com/ Fixed gear gallery]
* [http://sheldonbrown.com/singlespeed.html Single-speed Bicycle Conversions]
* [http://www.mtbr.com/faq/ssfaq.shtml Single-Speed FAQ]
* [http://www.singlespeedoutlaw.com/ Single-Speed Outlaw]
* [http://www.singlespeed.nl/ Singlespeed.nl]
* [http://www.singlespeedgallery.com/ Singlespeedgallery.com]
* [http://www.singlespeed-belgique.be/ Singlespeed Belgique French]
* [http://www.cyclofiend.com/ssg Cyclofiend Singlespeed Gallery]
* [http://forums.mtbr.com/forumdisplay.php?f=46 MTBR Singlespeed Forum]
* [http://thegearjunkie.com/single-speed-bike-trend-kona-paddy-wagon-column The Gear Junkie] - In-depth review of a single-speed bike.