Bull

iTrader: (5)

Yeah...so although I like this hobby, I am not very good at it, and usually have to learn how to do things by first failing at them. Like a rear brake job on my PBR brakes.

All I am trying to do is replace the rotors and pads, since they are worn. After way too much time and frustration, I am giving up until I get some e-help. No matter what I do, I can't get the pads to slip over the rotor...there just isn't enough clearance.

I have opened the bleeder screw and used a C-clamp to compress the piston as far as it will go.

I have a service manual, but it just isn't helping me overcome this.

There are two ways that I can see doing this. Here is the first one, that seems to be what the manual calls for:


The pads are installed in their position in the bracket, at which point you swing the empty caliper assembly into position over them. Doesn't work, too tight.

Here is the other option I can see:


Pads are installed in the caliper, and then swung up into position over the rotor and into the bracket. Hasn't worked, too tight. You can see in the pad facing you that it is getting gouged by the process.

Trying to force them into position has resulted in the metal backing plate for one of the pads to be loosened...obviously a sign that something is wrong:



So, not only do I feel like an incompetent, but I have to take the bus to work until I can get this fixed.

I'd greatly appreciate any help that you can offer.

Dave

Darkshot

iTrader: (4)

You sure you got the right parts?

BADMAN

iTrader: (13)

Have your part house check the part numbers. Also, maybe the old pads had a tapered edge to ease installation. Or, that style pad with the rear metal backing plate could be a little thick, maybe try another brand?

ryan91rs

iTrader: (1)

return them and get new ones. Those must be wrong. also don't get the type that is riveted on. get the ones that have the little spikes that hold it on. it's a special backing plate so it won't separate like that. good luck!

ebmiller88

iTrader: (7)

Have confidence, man, you're doing just fine and you have the right parts. The correct pads you have and need have a 413 in the number and by looking at them I assure you they are correct.

Now, I do NOT see what the issue is. If you used a clamp and pushed the piston in, the rotor should slide right in there especially on the PBR calipers. Are the guide pins sliding easily?

Ed

Bull

iTrader: (5)

Thanks for the input, Ed...I know you are a brake genius.

I don't get it either...it's the kind of job that I assumed would give me now trouble!

What guide pins are you referring to?

Here is a pic of the piston, after I compressed it as far as I could with the c-clamp. Can you tell anything from this pic?



Someone mentioned that if I need the extra bit of clearance, I can removge the metal backing plates from the pads, and just coat them withy anti-seize. Seems that I shouldn't have to do that, but I might try it?

JamesC

iTrader: (5)

The rubber boots protect the pin (looks like you've removed one already). Both probably should be removed and relubed.

JamesC

dr1

Ive never tried to swing one into place like that, ive always removed both pins before doing it, so i dont know, but perhaps thats what giving you the issue?

Z28 MeTaL HeAd

Agreed, same here. I do it like that as well.


Try and unbolt the bottom caliper bolt as well and see if you can 'wiggle' the caliper on with the pads, thats how i normally do it and its worked every single time.

Bull

iTrader: (5)

Can I get some additional clarification about these guide pins...can someone maybe circle them for me in the pic above? The only rubber boot I removed was the one on the bleeder screw...I do not see or know the function of any "guide pins."

The method I am using is what the factory service manual seems to call for, but I'll try anything at this point. However, the bottom caliper bolt seems inaccessible without removing some of what appears to be e-brake hardware/bracketry...is this accurate?

JamesC

iTrader: (5)

You can see the boots, which protect the guides, in the following pic. They're black pieces placed between the red carrier and the alum caliper:

https://www.thirdgen.org/forums/atta...s-89-lline.jpg

As I understand it, the pins allow the caliper to float/move a bit.

JamesC

Bull

iTrader: (5)

Thank you, James.

Now that I know what they are, I can say that I have not removed any of them....

JamesC

iTrader: (5)

In your last pic, one appears to have been removed. Oops, wrong.

JamesC

Mongoose

iTrader: (2)

I ran into this same type of problem when I installed my drilled and slotted rotors. Check to see that you have the pads in their correct position. What I mean by this is that mine had small "locator nubs" on one end of the metal backing on one of the pads that allowed them to fit on only one side (which I think was the outside opposite the piston). Once I got this figured out they just slid right on.

Bull

iTrader: (5)

Woohoo, progress has been made!

I tried to compress the pistons further by again opening the bleeder screw and using the old brake pad in between my c-clamp and the piston. Could not compress it anymore.

So, I decided to take the advice of a few people to just remove the metal backing plates from the two pads to gain that extra bit of clearance, and to smear anti-seize on the pad back to eliminate noise. It worked, as I gained just enough clearance to get the calipers back into position!

Now, I just need to bleed the brakes and see if they work...I ran out of time tonight, and don't want to rush it. Wondering if I should buy a brake bleeding tool i.e. Mityvac, or just do it with gravity...?

On another note, how much space is there supposed to be between the two new pads and the rotor? I see no visible space, and am wondering how the rotor spins freely? basic question, I know, but I honestly don't know the answer.

Thanks to all who have helped.

brandotron

iTrader: (2)

In my experience, there's always a tight fit between the pad and the rotor at first. I usually don't see any visible space either. Once you get everything back together, stomp the brakes a couple of times. It should get the pads, pistons, et al, back into alignment.

ebmiller88

iTrader: (7)

No visible space, you're golden. I usually skip the pad spacers like you did.

Ed

Bull

iTrader: (5)

Ah, such good news.

ebmiller88

iTrader: (7)

The guide pins are what the caliper bolts to. They fit inside the abutment bracket and NEED to have good seals and be lubed very well to allow the caliper to slide back and forth as the pads wear and take care of any runout issues with the rotor. I lube mine up with the same lube that Spohn sells, the white sticky stuff and it works very well. Keep the pins sliding good, once they freeze up you'll have pad wear issues.

PS..for anyone interested, the rotors Bull used are the ones that need to be used when you install these PBR rear brakes onto a drum axle rear. They have a larger ID and will give you no installation problems and keep you from having to have the axle flanges turned down.

Ed

Bull

iTrader: (5)

Thanks, Ed.

I guess the idea of "pins" confuses me, since the boot has a bolt that goes into it, which I removed the drop the calipers down. Is the bolt the pin in question?

Should I remove the bolts and get some lube in there, then?

Also, how the heck can you tell what rotors I used just from the pic, no part numbers? Impressive!

ebmiller88

iTrader: (7)

Yes, pull the bolts (IE pins) and lube them up good, make sure the seals have no cracks in them otherwise moisture can get in there and lock them up.

After doing this stuff for a while I can pretty much look at the casting and tell what you have. It's a gift...

Ed

Bull

iTrader: (5)

My wife wasn't around to be the "pedal pusher" so I went with gravity bleeding. Slow, but reliable.

I took the car out for a short test drive, and the brakes seem to be working well. I'll drive it on the highway to work tomorrow or Friday to do some aggressive braking and start to get the new parts broken in.

As a bonus, there used to be an annoying metallic squeak when making lower speed left turns. I always thought it was from the front of the car, but it is totally gone now...sweet.

I appreciate everyone's help here...I wonder how I ever got by without the net back in my younger days lol.

ws6transam

Thread up from the dead:

I had the very same problem today. Some of you know me, and you know that I've been at this for a very long time. So this came out of the blue, when I attempted to load my rear PBR's with some new Hawk HP+ pads. The driver-side went fine: I pushed in the piston and loaded the caliper, then swung it into position. There was about .080" of gap between the rotor and the piston once it was locked in.

Then I did the passenger side. I pushed the piston in as far as it would go, then attempted to load the caliper. When I went to close it, I realized I had a big problem, as there was .130" of interference between the new pads and the rotor. The piston literally wouldn't go in any further. I squeezed with the C-clamp but there was interference with the emergency brake yolk, which wouldn't go in any further. It was as if the caliper piston was fully seated!

..Then I took a break. Once I had my break I got out the laptop, found this thread, and read it. Then I figured I hadn't squeezed the caliper hard enough with the clamp. That didn't work, either. The piston face that touches the pad was frozen to the emergency brake yolk. Then I got out the big lead hammer and a brass bar, braced the back of the caliper, and beat on the piston face for all it was worth. Finally the yolk broke loose from the piston face, and I was able to push the piston in another .200" to yield the proper clearance.

So there you go: Additional information. If you cannot get the piston to go in far enough to clear the new pads, remember this:

The PBRs have TWO pistons: The outer piston, which is actuated by hydraulic fluid, and an inner piston, that floats inside the outer piston. The inner piston has a shoulder that rests on the emergency brake yoke, so that the E-brake can push the inner piston (via the yoke) outwards to actuate the brake pads. The inner piston therefore can be pushed outwards by either of two forces: A cable actuated lever, or by the hydraulic piston face that resides behind the inner piston.

Therefore, if you can't get that piston to go in far enough to clear the pads, give it a twist or a pull. If it is not free of the yoke, then it's frozen to the yoke and needs to be separated in order to get it to move properly.

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