Here simple video so you can see it.
http://bicycletutor.com/calculate-chain-length/
And by the way you shouldn't be cross chaining if you can help it.
Get off the lg chain ring and shift to a rear cog that works for you.
I might also add that I dont think the chain is the issue with your speed trouble....
Last edited by JTGraphics; 08-10-10 at 07:58 PM.