I have a 2011 hardrock sport disc. So far the first thing has been the brakes. I upgraded to hydraulic shimano SLX. Those are pretty high end and, being perfectly honest, probably a little overkill for what the bike is. But I found a great deal and they're awesome.
The stock avid BB5's are really not great. Hydro brakes have better modulation, more power, less need to readjust, etc. The BB5's I had to adjust constantly after rides. Not so with the hydros. Don't spring for low end hydros though.
For what it's worth, avid bb7's are good. probably the best mechanical discs you can buy, and not a whole lot more than bb5's, if you prefer to simply stay with mechanicals.
next thing I want is also a fork. honestly the fork is probably going to be the biggest upgrade for the whole bike, with brakes being a close second, IMO.
Last edited by ESW116; 01-31-12 at 06:58 PM.