I see in some threads bikes having the pistons drag from the not retracting completely. I used to run the caliper department of Rebco Racing Enterprises in the mid 90's. Whenever we had race car drivers complain that once the brakes heated up they would drag so the solution was to change out the square piston o-ring with a round one. The round ones retracted more than the square ones relieving this issue. I'm thinking it might work on these calipers also.
