Bikes with chains may be becoming an endangered species. Belt-driven bikes, which were introduced by boutique bike makers a couple of years ago, are just starting to hit the mainstream. Trek has introduced two new urban bikes for 2009 with belt drives rather than chains, and they look pretty sweet. The benefit to a belt drive system over a chain and shifters system is that it won't stretch and break over time like a chain, weighs significantly less, stays clean (and keeps your cuffs clean) and is quiet. The downside? It's more expensive. The two bikes Trek has unveiled, the District and the Soho, will run you $930 and $990, respectively. But as with all new tech, the prices are always highest right when it starts hitting the mainstream. Look for bikes with belt drives to start coming from many more big bike companies for much less in the coming years.