<Li> An eccentric hub or bottom bracket allows the off center axle or bottom bracket spindle to pivot and change the chain tension . </Li> <Li> A ghost or floating chainring is an additional chainring in the drive train between the driving chainring and sprocket . The top of the chain moves it forward at the same speed that the bottom of the chain moves it backwards, giving the appearance that it is floating in the chain . </Li> <Li> A magic gear--the right math can calculate a gearing ratio to fit a taut chain between the rear dropout and bottom bracket . Also, using a chain half link and slightly filing the dropouts to increase the width of the slot increases the chances of finding a magic gear . It is worth noting that the magic gear setup is controversial, due to inevitable chain stretch and subsequent slippage that can lead to serious injury . </Li> <P> Separate chain tensioning devices, such as the type that attaches to the dropout (commonly used on single speed mountain bikes) cannot be used because they are damaged as soon as the lower part of the chain becomes tight . </P>

What is the point of a fixie bike