my driver side rear brake pad is rubbing against the rotor slightly. I can hear it when i drive slowly with my head out the window. I replaced the pins and boots recently and also just installed new ceramic pads and slotted/drilled rotors from R1 concepts. the pins slide out fine when the brake is off the car. The pad spreaders are on the pads correctly and everything is greased up correctly. I also have ls400 brakes in the front. I bled all the lines. the piston does not seem to be seized, it moves in find with a c-clamp. I cant figure out why it is rubbing. any ideas?