Sabtu, 09 April 2011

Fixed-gear bicycle


fixed-gear bicycle (or fixed-wheel bicycle, sometimes known in the USA as a fixie) is a bicycle that has no freewheel, meaning it cannot coast — the pedals are always in motion when the bicycle is moving.
The sprocket is screwed or bolted directly onto a fixed hub. When the rear wheel turns, the pedals turn in the same direction. This allows a cyclist to stop without using a brake, by resisting the rotation of the cranks, and also to ride in reverse.
The track bicycle is a form of fixed-gear bicycle used for track cycling in a velodrome. But since a "fixed-gear bicycle" is just a bicycle without a freewheel, a fixed-gear bicycle can be almost any type of bicycle.
Traditionally, some road racing, club cyclists used a fixed-gear bicycle for training during the winter months, generally using a relatively low gear ratio, believed to help develop a good pedalling style. In the UK until the 1950s it was common for riders to use fixed-gear bicycles for time trials. The fixed-gear was also commonly used, and continues to be used in the end of season hill climb races in the autumn. A typical club men's fixed-gear machine would have been a "road/path" or "road/track" cycle. In the era when most riders only had one cycle, the same bike when stripped down and fitted with racing wheels was used for road time trials and track racing, and when fitted with mudguards (fenders) and a bag, it was used for club runs, touring and winter training.By the 1960s, multi-gear derailleurs had become the norm and riding fixed-gear on the road declined over the next few decades.Recent years have seen renewed interest and increased popularity of fixed-gear cycling.
In urban North America fixed-gear bicycles have achieved tremendous popularity, with the rise of discernible regional aesthetic preferences for finish and design details.
Dedicated fixed-gear road bicycles are being produced in greater numbers by established bicycle manufacturers. They are generally low in price and characterized by relaxed road geometry, as opposed to the steep geometry of track bicycles.
Fixed-gear bicycles are also used in cycle ball, bike polo and artistic cycling.
A fixed-gear bicycle is particularly well suited for track stands, a manoeuvre in which the bicycle can be held stationary, balanced upright with the rider's feet on the pedals.
In slippery conditions some riders prefer to ride fixed because they believe the transmission provides increased feedback on back tire grip.
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.
Riding fixed is considered by some to encourage a more effective pedaling style, which is claimed translates into greater efficiency and power when used on a bicycle fitted with a freewheel.
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 for the novice rider, as the pedals can strike the road, resulting in possible loss of control.
A fixed gear bicycle has fewer moving parts than a multi-gear bicycle and requires less maintenance
ome 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.
Other riders dismiss riding on roads without brakes as an affectation, based on image rather than practicality. Riding brakeless can be dangerous, is prohibited by law in many jurisdictions, and may jeopardize the chances of a successful claim in the event of an accident
















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