I just installed a 92 z28 rear 3.42 posi in place of my old 2.73 drum rear. I bought new PBR calipers from Thirdgen ranch for the rear. my rotors were used rotors in good condition with a little rust. I believe I hooked them up correctly, they were a real tight fit going onto the caliper. Now it seems the rear rotor just slides onto the lug bolts without any other way of securing them???.... anyway I hear a slight scraping sounds, kinda like someone is sharping a knife from the inside of the car. I tried to listen on the outside while my buddy drove it and cannot hear it from the outside??

 

did you check the clearance between the caliber mounting bracket and the rotor? gm used shims under the axle flange to move the caliper brackets to correct this. The rotor does just slide on and the axle flange centric centers the rotor.

 

hmm, I did notice the mounting bolts were sticking thru a bit, didnt look like they would touch when I put them on, Im not the smartest guy in the world but im kinda not understand what your saying about shims, can you explain to me a bit. are the mounting bolts suppose to stick out a little?

 

did you replace the little metal spring looking pad retainers?

 

This is what it came with, the calipers, then I bought pads and put the pads inside the calipers, the only springs I seen were the 2 on the piston and then the ones on the bottom of the actual pads that hold the pads in the calipers.

 

What shims is tuneperformance talking about? like a spacer?

 

Maybe those PBR's are different then my 97 camaros, but it has little metal spring looking retainer things that seem to isolate the pads from the calipers, anyways mine makes scraping noises without them.

 

there are two ways to move the caliper mounting bracket, one with shims on the axle flange witch I like the best or two with washers between the caliper mounting bracket and anchor plate bracket.



http://andyz28.com/catalog.htm

 

You can see the shims (part #36 in the diagram above) in pic two of the following write-up:

https://www.thirdgen.org/forums/faq-...iscs-89-a.html

JamesC

 

Part #36 in his second picture. I'm not sure if these are still available though? And you have to pull the axle to change them out.- sorry beat me to it Andysz28 still has them


What is part #25 in the caliper break down? I don't remember this? Or is it the clip that goes on the side of the this metal frame to kind of hold that assemblage together?

 

25 was the clips used during the assembly line to retain rotor and drums. The shims are no longer available but I had included the link to andy's z28.com on post 8.

 

yall are still talking another language, are "shims" the spacer plates that are on the outside of the drums? I still have those...

 

this is only happening on my rear driver , and I can see where the brake caliper is rubbing on the rotor. Passanger side is fine no issues, I can hear ti scraping on right turns.

 

Look at the above post between the axle flange and caliper mounting bracket #36

 

Well I just took the whole weekend to re-due my ENTIRE suspension front and back to include a 3.42 gear swap and PBR's. Im too worn out to take the whole rear off take my axles out to put that spacer on, I just threw in some washers between the caliper and the mounting plate... works great no more grinding

 

so the bracket was rubbing on the rotor ?

 

Yea that was the problem you were spot on. those Shims are missing from both sides but for some weird reason the passenger side has good spacing without the shim or washer

 

Those were installed to compensate for axle flanges being inaccurate in offset.

 

Note that in the thread I linked you to, my rear only required one. Apparently, for the sake of information, the 9-bolt didn't require shims.

JamesC

 

Humm, so you didn't properly place them between the backing plate and axle flange--or am I misinterpreting?

JamesC

 

No, Not between the axle flange and the backing plate. I put them between the backingplate and the caliper, it seemed to do the same thing would it hurt anything?

 

It will do the same thing that way but you are putting more stress on the bracket and bolts.

 

roger that I will be putting them between the axle flange/backing plate,I have another question for you. are the pads OK to touch the rotor? I read in a post somewhere the rear should spin freely? is that without any pad rubbing?

 

you may feel slight resistance as long as the caliper isnt stuck applying the brake your goto go.

 

did you replace the proportioning valve ?

 

OK, I drove it on a 2 1/2hr drive today after finishing the above.. I thought I fixed it with them washers but I may have to space it more. If its rubbing ever so slightly could it mimmic the sound of a bad diff. like the sound of a spooling turbo?

 

I did replace the prop valve. I bought one from someone who c\said it was a disc/disc. but im afraid the rears arnt getting the pressure, is there anyway of checking a number on it or something?

 

https://www.thirdgen.org/forums/brak...e-upgrade.html

I have never experienced a brake pad or shoes drag ever cause nose excessive heat and burning smell yes. The recommended clearance is for metal expansion.

 

If I hold the brake and step on the gas the fronts will hold and the rears will spin. That tells me there not getting the pressure and also the Brake Light is ON

 

Perhaps the calipers require a rebuild--or the slider pins a thorough lubing at the very least. In response to your PM, there are no numbers to ID a combination valve.

Normally the light comes on and stays on when part of the system has failed.

Here's a bit more info from the manual:

"The pressure differential warning switch is designed to constantly compare front and rear brake pressure from the master cylinder and energize the warning light on the dash in the event of a front or rear system failure. The valve and switch are so designed that the switch will latch in the "warning" position once a failure has occurred. The only way the light can be turned off is to repair the failure and apply a pedal force to develop approximately 450 psi line pressure."

BTW, will the parking brake hold? Or do the rotors spin with it on?

JamesC

 

I think I fixed it or it fixed itself. I went out and got them springs for the Cheap Prop Valve Upgrade thread and installed... the brake was very very stiff while trying to bleed, I could not get anything to come out. I Put back in the stocker, bled the lines again.. the right driver side didnt have much pressure but I bled them the best I could. put everything back together started the car and the brake light was still on... drove a little and it seemed to no be fixed. Turned the car back on and the brake light was off and I dont feel that resistance I had before. Wierd

 

There is a small set screw that adjust the pad to make good contact when the e brake is applied as well. I had to adjust this when I installed mine as well, I was getting that same kinda sound as one side of the pad was gently staying in contact with the rotor at all times.

 

"Free Travel" is addressed in the link in post #9, should more info be required.

JamesC

 

I had a similar problem when I installed my PBR discs on a 86 rear end that I put in the car. Used washers to center the carrier on the rotor, and they've been on maintenance free for 8 years now. Pretty easy fix.

Will

 

Yea I ended up doing the exact same thing. It was only off on the driver side rear, my pass side had natural perfect spacing... BUT I started hearing that scraping on the pass side, But there is no friction on the rotor. If you know why that would be id like some of you knowledge.