I am thinking about using two Sram RED BB30 cranksets. One with 50/38 and one with 50/34 for in the mountains.
I was wondering If you can use my SRAM Red 2011 model (compact BB30) and the new 2012 model (compact BB30) without changing or adjust the front derailleur, spacers BB30 ect. each time a swap cranksets.

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Specialized Tarmac S-works SL4
http://i891.photobucket.com/albums/ac11 ... 11af34.jpg

I believe you would have some chain rub on the 2011 Red Crankset when cross-chaining. From my understanding, the 2012 Sram Red crank has around 1.5mm more lateral spacing from small chainring to big chainring.

It also might mean small adjustments would need to be made to the FD when switching, but I'm not sure.

What size cassette are you running now? Maybe it would be easier to just run the 2012 Red crank and switch to an 11-28 when headed into the mountains.

if you really want to go between 50/38 and 50/34, just buy a 34 or 38 chainring, whichever you don't have now, and swap it on the current cranks

cheapest option, and no need to adjust the front mech