changing big chain ring
 

Hey, im planning on changing my big chain ring this weekend from a 48 t worn out one to a relatively new 52t I had laying around. I vaguely remember hearing that the front DR should be ~2mm above the ring, but is this the top of the DR or the bottom?

Take a look at your current setup and replicate it with your new chainring. Take a picture to help remind you. The 2mm you're referring to is the space between the very top of the tooth and the bottom of the cage.

Shift your front der to the large chainring then take a penny and stick it into the front of the derailleur between the bottom of the der cage and the chainring teeth. It should just fit and be pretty snug. Don't forget to check that you keep the derailleur cage parallel to the rings if you have to make any adjustments.