Originally Posted by
TRaffic Jammer
Concentric BB's or hubs work too if you have too much money, but apply the KISS principle and you generally can't go wrong.
i believe the word you are looking for is eccentric. concentric is when two objects share an axis (a normal hub/bb) and eccentrics are not for people with too much money. they are for people that want safe and proper chain tension. there is a reason why tandems use eccentric bottom brackets. chainrings are not perfect and chains stretch...
if your just running a single speed get a chain tensioner. they are cheap, easy, care free, and let you change sprockets at will.