Follow these steps in this order... 1. Give the brake a fresh bleed, preferably a bath/bucket bleed (check out the wiki if unsure) 2. What frame are you using? Even with a built in booster some can flex a lot, so check for that and if so get yourself an appropriate booster. 3. Get some TNNs as said earlier and whack em on a fresh grind (check out the wiki if unsure) itis easy to do and if you don't have a grinder theres surely your aunts, cousins, friend bob's, dogs, vet's son who will have one? Or you can pick one up for just over a tenner. That is what I would do if my brake was spongey