Something keeps nocking pretty loudly as i drive down a bumpy street so i took my wheel off to have a look and when i spin the disc backwards and forwards, the rear pad that the piston pushes moves with the disc and hits the caliper which is making the banging sound, is there meant to be any clips of anything there? or should i change my pads? they still have a lot of life left in them though. my car is the 1.4 mk5 by the way