What ever you do, don't shift into the lowest(big cog) in the back if you are not sure 100% sure that you set the low limit screw correctly because the chain could go into your rear spokes, messing up the derailleur, derailleur hanger, wheel and maybe causing you to crash.
One way to check is to put the bike in your stand, shift the rear derailleur at the hardest(small cog) and then pedal the bike with your right hand while pushing the rear derailleur with your left hand as far as it can go (towards the spokes). If the chain falls off towards the spokes, then you need to screw the low limit screw in a bit until the chain stays in place on the low(big cog) when you push the rear derailleur all the way in.
Last edited by 531phile; 01-23-11 at 05:57 PM.