on a
Burley tandem bicycle, held in place with two
set screws The term is also used to refer to the device often used on
tandem bicycles with timing chains,
single-speed bicycles with a rear
disc brake or an
internal-geared hub, or any bicycle with vertical
dropouts and no
derailleur, to allow slight repositioning, fore and aft, of a
bottom bracket to properly tension the chain. As a standard sized bottom bracket threads into the eccentric, an oversized bottom bracket shell is required to accommodate the eccentric. ==Gallery==