A fixed-gear bicycle (fixed wheel bicycle fixie) cannot coast — the pedals are always in motion when the bicycle is moving. The sprocket is screwed directly on to the hub and there is no freewheel mechanism. 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.Track cycling in a velodrome has always used fixed-gear track bikes, but fixed-gear bicycles are now used on the road.- a trend generally seen as been led by bicycle messengers.
Most fixed gear bicycles have just one gear ratio.(In the UK, "fixed-wheel" is the normal term for the subject of this article -
meaning the opposite of freewheel, and "fixed-gear" refers to a single-speed bicycle).
(from Wikipedia)
