Ok here is the deal that drives me crazy
Got a 76 rebuild the hole rear end every thing is new
Here is the issue that’s making me mad.

Bleed the rear caliper got a rock sold pedal sounds good right.
drive it around rock solid than when I drive over 45 miles and a longer period of time the rear breaks starts to fade only the back brakes and there are no leakages.

Put is on the bridge open up the bleeders got air ****!!
bleed it again rock solid drive it for one hour and the brakes starts to get worse and so one.
Bleed it for at least 20 times minimum with no air
rebuild a lot of brakes for customers al fine but my night mare corvette
cant seam to get it right

So this is what I was thinking the corvette brakes have a spring behind the pistons .Is it possible that when de disc aren’t running straight the pistons are moving rapidly and suck up air while driving and not operating the brakes ( I know Porsche had this issue)
Ore will a little wheel baring play end up in this problem
O and yes replaced the master cylinder.
Hope some one knows a solution to this strange problem.

Thanks ,
Leon

brake expert needed

 

Check the run out on the rear rotors first.

 

if there's a run out how do I straight it out
thanks fore the reply

 

Have seen this before your rear brake calipers are sucking in air while driving. You may have to much runout in your rotors or your calipers are bad or both. Thanks Dave

 

www.brakealign.com/

 

So the rotor's are brand new never had a new rotor that wasn't straight
the spindels is the only part that I didnt replaced they looked brand new

I there a nother trick to line them up like whashers hmmm dont think that will be a good thing.!!

 

If the rotors have minimal run out and your using off the shelf rebuilds, I'd recommend going to O ring calipers.

 

When I rebuilt my system I left the piston springs out. The system works fine. I am not suggesting this as a solution, only that the system will operate without the springs.

 

That was the best 8 minutes I've spent, Brakealign would be the way to go. Thanks Gene

 

Hey Pete..you say that you replaced everything..ok does this mean bearings also..I assume so..did you get the end play down low..I assume so..that leaves the spindle and rotor runout may be a little out..I have said this on many brake posts before..but..find a Procut brakelathe and get the rotors cut on the car..I know the shim thing works but this will true the rotors to the hubs..I got one and love it..it wont take much so don't let them cut the planet off them..couple thou is all that's needed..also make sure they know about the u joint bind in the rear with the wheels off the ground..I did mine when I rebuilt the calipers and new bearings on mine..no problems at all..of course I am also assuming that you have a run out issue..

 

It's not the rotors that are not straight- it's the spindle. They weren't true from the factory, nor were the rotors. They were assembled, riveted and final machined to make them a matched set. You've tossed out half of the matched set so have to start over. Read up on rotor runout on this site.

 

Wonder how many times that question has been asked?