I put a 4-wheel disc brake kit on my Cutlass 2 years ago. The only thing that has not been replaced is the brake pedal.

If I remember correctly the rear brake calipers are from a late 70's Trans Am.

I've been having trouble with the brakes for a while now and part of the testing was to replace the master cylinder.

While bleeding the brakes, I noticed that the driver's side rear inner pad was not parallel to the rotor but on an angle. The inner pad has a little pin sticking out that sits in one of 6 notches in the surface of the piston. It was not sitting in a notch but on the main surface of the piston causing the angle.

It looks like the gap between the pad and rotor is just the right size that the pad can pull away from the rotor enough for the pin to come out of the notch.

But it also looks like when this happens the piston rotates a little so that the pin and notch no longer line up which causes the pad to no longer sit flat.

I know these are Pontiac parts but does anyone know if the piston should even be able to rotate? The passenger side has the same gaps but does not have this issue.

Previous issues I've had with the brakes are rear brakes dragging (not sure if one side or both), a metal on metal scratching/rubbing sound (not the wear indicator type of sound), varying brake pedal travel and the brakes not fully releasing when I take my foot off the pedal. The dragging seems to have been resolved earlier this year, but I still sometimes get the sound, but only in very specific conditions (I think just a specific right hand curve), the brakes not fully release after a full stop and the varying pedal travel.

The pedal does not go to the floor or activate the warning light.