today i fixed my coworkers hydro road discs. shimanos.
basically the lever went all the way to the bar, and he had very low power.
so i remove the caliper from the frame and pump the lever
once. pads now move out a bit further and stay there.
reassemble. same problem.
investigate further. seems one piston is moving much further than the other. pump them out very far and clean the pistons with brake clean. then i push the "faster" piston in to try to get the sluggish one to move out. this works, and when i have that one out far i spray it with brake clean.
then i try to cycle them in-out a few times. and spray them a few times more with brake clean. when they are moving freely i drip one drop of oil on each one making sure it wont get on the pads.
then i set the distance i want the pistons sticking out, and assemble again on the frame. pump the brakes a few times and make sure its not rubbing.
done. now the lever wont go all the way into the bar anymore and both pistons move at the same speed. this took me about 10 minutes.
its BS like this that made me ditch hydros. long live the bb7!