c3 brake problem

[Tom Ferguson]

Hi everyone, I just replaced my brakes on the 1975 singray.
New o-ring calipers (from vbp of course) new rotors.
I used the speed bleeder in conjuction with the gravity method.
Brakes seem to work good but on every caliper one side of the pistons seem to be all the way in the bore not even touching the pads. On the right rear the caliper body is grinding away on the rotor. Is there a difference between the front and rear rotors? cause my new ones had no part #'s to speak of and the rotors look to be identical.

[Joe L.]

Re: c3 brake problem

Tom-----

There is a slight difference in the machining of the front and rear rotors; the castings, themselves, are usually the same. Some of the aftermarket rotor manufacturers machine the rotors so that one finished rotor services both front and rear applications. GM could have done it that way, too, but for some reason they didn't. Keep in mind, though, that the GM parts system NEVER supplied front rotors as a piece seperate from the hub; only a front hub/rotor assembly was ever offered. Delco now sells seperate rotors, but these are aftermarket-sourced pieces.

I doubt that your rotor/caliper contact problem is due to an incorrect rotor. However, check the parking brake drum inner surface. If it's a FINISH machined surface, the rotor is the correct one for the application. In those cases in which manufacturers do make a specific front and specific rear rotor, they usually don't FINISH machine the parking brake drum.

[Bill Wilkins]

Re: c3 brake problem

The brake calipers each have two bleed screws. If you missed the inner ones the pistons won't come out to play.