Derailer/Chainring Compatability
 

Putting together a new commuter/around town bike with some miscellaneous parts I've got lying around. Have a Deore XT front derailer and was wondering if I'm gonna have problems with the 52/42 tooth rings I have on hand. I've read that there can be some problems because of the xt derailer being designed for smaller chain rings.

Thanks,
Paul

Yeah sometimes you do run into problems.
Front derailleurs are usually rated to handle up to a specific range, and largest ring,
MTB derailleurs are rated lower than road derailleurs, so the cage might rub on the rings, or you will not be able to set it low enough for adequate shifting.
I use an XTR with a 34/48, but that's pushing it.

From what i've gleaned in the past few days, 48t seems to be the limit for 'MTB' style front derailleurs.

Since you have it there already, however, you might want to try it and see. I suspect (but this is just idle speculation) that if you are using indexed front shifting, it might not work, but if you are using bar-end shifters or some other friction-ish option, there might be a chance.

I've noticed that NOS road front derailleurs are pretty cheap on eBay. I got a brand new Ultegra triple for about $25 shipped, and the only reason i went for a brand new Ultegra model (instead of a used 105 unit or something) is because i'm vain and insecure and live vicariously through the envious looks my bike gets :p