Last night I swapped my standard SRAM Rival crank for a compact, also SRAM Rival and now I am having difficulty shifting the rear derailleur to my biggest gear (50-12). Before the swap everything was working fine and right now all other gears shift perfectly (although I avoid big-big and small-small due to chain rub). I didn't touch the limit screws and, in fact, the derailleur doesn't quite appear to be reaching the high limit screw. I did shorten the chain to big-big+1 so something chain related seems the most likely culprit but I am reluctant to start messing with anything without having any idea what is wrong.
FYI the bike is a Ridley Excalibur with full SRAM Rival. 50-34, 12-25.
86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.
Often, when doing a change on one end of the drive train, you'll end up having to make a minor DER adjustment on the other end. NOT uncommon!
I changed my BB a couple months back and had to do so on the rear.