I just built a mountain bike with Avid BB7 brakes and Shimano V-brake levers. I used the exact same configuration on another bike, and it worked beautifully. But on this one, the brakes are just weak as hell. I know that disk brakes are supposed to have a short break-in period, but I'm way beyond that now, and still no change. What's going on and how can I fix it?
Avid recommends breaking those discs and pads in with about 30 or 40 deliberately hard stops in order to build up a good foundation. If you've gone through that process a couple of times and still no dice, there could be brake fluid on the discs or pads. Some water or isopropyl alcohol should take care of that.