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A fixed-gear bicycle (or fixed-wheel bicycle, commonly known in some places as a fixie) is a bicycle that has a drivetrain with no freewheel mechanism. The freewheel was developed early in the history of bicycle design but the fixed-gear bicycle remained the standard track racing design. More recently the "fixie" has become a popular alternative among mainly urban cyclists, offering the advantage of simplicity compared with the standard multi-geared bicycle.
Most bicycle hubs incorporate a freewheel to allow the pedals to remain stationary while the bicycle is in motion, so that the rider can coast, i.e., ride without pedalling using forward momentum. A fixed-gear drivetrain has the drive sprocket (or cog) threaded or bolted directly to the hub of the back wheel, so that the pedals are directly coupled to the wheel. During acceleration, the pedal crank drives the wheel, but in other situations, the rear wheel can drive the pedal cranks. This direct coupling allows a cyclist to apply a braking force with the legs and bodyweight, by resisting the rotation of the cranks. It also makes it possible to cycle backwards.
As a general rule, fixed-gear bicycles are single-speed. A derailleur for gear selection would introduce chain slack, which would interfere with braking. Gear selection can, however, be accomplished with the use of an internally geared hub. For example, a Sturmey-Archer fixed-gear three-speed hub is a fixed-gear multi-speed arrangement. Most fixed-gear bicycles only have a front brake, and some have no brakes at all.
Descending any significant gradient is more difficult as the rider must spin the cranks at high speed (sometimes at 170 rpm or more), or use the brakes to slow down. Some consider that the enforced fast spin when descending increases suppleness or flexibility, which is said to improve pedalling performance on any type of bicycle; however the performance boost is negligible compared to the benefits of riding a free wheel.
When first riding a fixed gear, a cyclist used to a freewheel may try to freewheel, or coast, particularly when approaching corners or obstacles. Since coasting is not possible this can lead to a "kick" to the trailing leg, and even to loss of control of the bicycle. Riding at high speed around corners can be difficult on a road bike converted into a fixed-gear bicycle, as the pedals can strike the road, resulting in loss of control. Proper track bikes have a higher bottom bracket to compensate for the constantly spinning cranks and largely mitigate this problem.
Many urban fixed-gear riders think brakes are not strictly necessary, and brakeless fixed riding has a cult status in some areas. Brakes and their cables are said to add extra bulk to the simple appearance of a fixed gear bicycle, and they prevent trick manoeuvres that involve spinning the front wheel in a full circle, unless equipped with special 360° freedom "detangler" system already used on BMX bicycles.
It is possible to slow down or stop a fixed-gear bike in two ways. The first, most efficient, and least stressful on the rider's body is by resisting the turning cranks as they come up and around, shedding speed with each pedal rotation. The second way, less efficient but more showy, is to bump or skid the rear wheel along the riding surface. Such a move is initiated by shifting the rider's weight slightly forward and pulling up on the pedals using clipless pedals or toe clips and straps. The rider then stops turning the cranks, thus stopping the drivetrain and rear wheel, while applying body weight in opposition to the rotation of the cranks. This causes the rear wheel to skid, and slow the bike. The skid can be held until the bicycle stops or until the rider desires to continue pedaling again at a slower speed. The technique requires practice and is generally considered dangerous when used during cornering.
For a variety of reasons, many cyclists choose to convert freewheel bicycles to fixed gear. Frames with horizontal dropouts are straightforward to convert, frames with vertical dropouts less so. One method is to simply replace the rear wheel with a wheel that has a track/fixed hub. Another is to use a hub designed for use with a threaded multi-speed freewheel. Such a hub only has the normal right-handed threads for the sprocket and not the reverse threads for the lockrings used on track/fixed hubs. The sprocket on a hub without a lockring may unscrew while back pedalling. Even if a bottom bracket lockring is threaded onto the hub, along with a track sprocket, because the bottom-bracket lockring is not reverse threaded, the possibility still exists that both the sprocket and locknut can unscrew. Therefore, it is recommended to have both front and rear brakes on a fixed-gear bicycle using a converted freewheel hub in case the sprocket unscrews while backpedaling. It is also advisable to use a thread sealer for the sprocket and bottom bracket locking. The rotafix (or "frame whipping") method may be helpful to securely install the sprocket.
Usually, the rear hub is the best component on which to perform chainline adjustments, especially on threaded hubs. If a track hub is used, it is better to operate on the bottom bracket or - for minor shifts - on the crankset. The same occurs if a flip-flop hub is used, because the chainline should be the same in both sides (freewheel and fixed gear).
Moreover, bike messengers and other urban riders may ride fixed gear bicycles in alleycat races, which are normally held in city streets, including New York City's famous fixed-gear-only race Monstertrack alleycat. Similarly, Wolfpack Hustle began in 2005 simply as ride bringing together fast-paced bicycle riders with the common love for riding and has expanded to an internationally known race series that takes place in Los Angeles, California. The group has managed to receive sponsorships from several well-known companies including Castelli, which is an over-130-year-old Italian cycling clothing brand, helping spread interest and knowledge about the group and the races they hold. In San Francisco, California, Red Bull holds Red Bull Ride + Style events, which bring together both track and freestyle fixed-gear riders from around the world for competitions.
It is imperative (for road riding, at least) that the chain is sufficiently tight that it is impossible for it to derail from either the chainring or sprocket. This generally equates to "no visible slack". A derailed chain can cause a variety of undesirable consequences, such as a locked rear wheel or, worst of all, destruction of the frame if the chain becomes caught around the pedal spindle and pulls the rear triangle forwards. On a fixed-gear bicycle without hand brakes, even a relatively benign derailment means a total loss of braking ability. Tensioning aside, a chain is significantly less likely to derail if the chainline is accurate and the chain is a traditional "full bushing" type with limited lateral flexibility. Because the difference between a tight and a slack chain equates to only very minor elongation of the links, chain tension should be visually checked at least weekly, especially if the bicycle is ridden in wet or dirty conditions.
Several factors contribute to the recent [needs update] rise in popularity of fixed-gear bicycle. A rider from Stockholm interviewed for an article about the phenomenon notes that riding a bike imparts a feeling of freedom to the rider. One is free to go wherever one wants, whenever one wants. A sense of belonging is also important; as the rider says, "all who cycle are my friends". Riders unknown to each other commonly greet each other when on bikes. As in many subcultures, this feeling of belonging is a key factor in recruiting and retaining participants.
A fixed gear bike is also used in the circus arts (artistic cycling). When the saddle and handlebars are at the same height, an acrobat can stand on the handlebars and saddle and perform acrobatic exercises, sometimes involving multiple people, while continuing to circle the circus ring. It can be found as a niche sport in many countries. In addition to better speed control, the use of a fixed gear bike allows the artist to ride the bike backwards and/or only on the back wheel.[further explanation needed]
The 2012 film Premium Rush uses a "fixie" as a running plot device. Wilee, the lead character played by Joseph Gordon-Levitt, works as a bike messenger in Manhattan, and his fellow riders rib him about his enthusiasm for his fixed-gear steel-frame bike with no brakes. He avoids one confrontation by pedaling the bicycle backward, and he successfully weaves through dangerous traffic, but he also gets into accidents because the fixed-gear style abets his avidity for speed. Wilee says, "I like to ride. Fixed gear. No brakes. Can't stop. Don't want to, either." 2b1af7f3a8