Single-speed bicycle

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Single-speed mountain bike

A single-speed bicycle is a type of bicycle with a single gear ratio. These bicycles are without derailleur gears, hub gearing or other methods for varying the gear ratio of the bicycle.

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.

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[edit] Advantages and disadvantages versus multi-speed bicycles

[edit] 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.[citation needed]

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 by virtue of the wider base in the triangle formed by the hub, spokes and rim.[citation needed]

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

[edit] Disadvantages

As the single-speed bicycle lacks alternative gearing ratios, it is inherently less versatile, as it cannot be pedaled efficiently outside of its single gearing range. Without lower gearing options, the single speed bicycle is generally more difficult to pedal up extremely steep terrain. Conversely, its dedicated gear ratio also limits top speed, and is slower than a multi-geared bicycle on flat or descending terrain once bicycle speed exceeds the rider's ability to maintain continuing increases in cadence (pedaling revolutions per minute), typically 85-110 rpm.

[edit] Types of single speed bicycles

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While Track 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. This typically requires the rider to be more fit or skilled than the average rider in order to traverse the same terrain. 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.[citation needed] Depending on the situation, a messenger may prefer a mountain bike based single-speed, which can roll over many obstacles, or a fast and light road bike-based single-speed.

Statements by cycling industry representatives and journalists[who?] fueled the perception[citation needed] 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 either constructed without suspension (fully rigid) or with front suspension forks. "Full-suspension" single speeds offer increased weight and complexity in contrast to the "light and simple" qualities of un-suspended single speeds. Because one of the goals of a single speed mountain bike is simplicity, it is extremely uncommon to run across a full-suspension single speed bicycle.

[edit] 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 bracket[1] or in the rear hub.[2] 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 Singlelator[3] , can be used to take up chain slack. As well, finetuning the combination of chainring, cog, and chain length may suffice until the chain develops significant wear.

Throughout the years bicycle designers have produced belt-driven bicycle.[citation needed] 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. Also replacement of the one-piece belt requires traditional diamond bicycle frames to have a special split chainstay.

[edit] References

  1. ^ "Bottom Bracket Eccentrics & Shells". http://www.philwood.com/Eccentric%20Shell.htm. Retrieved on 2007-10-19. 
  2. ^ "The White Industries ENO Single Speed Fixed/Free Hubs". http://www.sheldonbrown.com/harris/white-hubs.html. Retrieved on 2007-10-19. 
  3. ^ "Singlelator". http://www.surlybikes.com/parts/singleator_pop.html. Retrieved on 2007-10-19. 

[edit] See also

[edit] External links

Retrieved from "http://en.wikipedia.org/wiki/Single-speed_bicycle"
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