An eccentric wheel of a bicycle including a wheel body, a pair of tracks formed in parallel in the wheel body, one or more holes formed in each of the tracks, a block slidably engaged between the tracks for supporting a wheel axle of the bicyle, a pair of pins slidably engaged in the block and extendible...http://www.google.com/patents/US5249847?utm_source=gb-gplus-sharePatent US5249847 - Eccentric wheel of a bicycle
