My road bike has a full Dura Ace 7900 drivetrain. The crankset has 53/39 rings. I will be participating in some heavy duty climbing in Colorado in a couple of months and have been considering temporarily replacing the crankset with a compact crankset while I am in the mountains.
My question is... if I swap out the current 7900 crankset for a 7950 (Dura Ace compact) will I need to replace the BB as well? If the answer is 'yes' then when I swap back to the 7900 crankset, should I replace the BB with the original one?