FAQ: Brake Rotors and Pads

Our pistons do NOT rotate as they extend. That tab is there to prevent the piston from rotating. The e-brake uses a mechanical screw, which is why you have to 'wind' them back in when you replace the pad. The grooves in the piston need to be lined up to go around that tab when you put it back together.

deekster_caddy wrote:

Our pistons do NOT rotate as they extend. That tab is there to prevent the piston from rotating. The e-brake uses a mechanical screw, which is why you have to 'wind' them back in when you replace the pad. The grooves in the piston need to be lined up to go around that tab when you put it back together.

Good to know. So do all rear pads for our cars have this tab?
And if i hit the E brake it will cause the piston to rotate out, but not during normal operation?

Matthew

The piston never rotates during normal use, e-brake or not. The tab/slot keeps it from rotating. The e-brake turns a screw on the inside which forces the piston out. That's also the 'adjustment' and the screw prevents the piston from retracting too far back. So when you go to replace pads, you need to screw the piston back in - that's the only time the piston ever turns.

Every rear-disc GM I've seen since the mid-90's have been the identical way. My '94 Regal was like this. The rear-disc conversion kit I had for my '86 Suburban used this too, but the calipers were from a '78 Eldorado.... I never needed to replace the pads but based on the e-brake setup I think it was the same design. With the exception that the '78 Eldo calipers leaked brake fluid...