Hi there looking for advice on the rear piston on my caliper, changed front disc n pads no problem but rear piston in caliper does not seen want to screw back into housing, rear pads pretty worn and disc also so piston got to go fair way back into housing removed hand brake cable and taken lid off reservoir ,not got "special" tool but using circlip pliers turning clockwise can get piston to rotate but does not want to screw back into housing? any tips or tricks I'm missing out on ? got to use car in am so put old gear back on but would like to sort? any help n adnice appriciated. Houch.