Rear Brake Problem (94+ rears)

[Robby1870]

For those that don't follow my ramblings in the Whatever thread, I drove the STE a couple of weeks ago and noticed a "hot" smell when I would stop, coupled with the fact that the car would not "coast" like an automatic car should. When I got back I noticed a lot of heat from the left rear. I looked a front of the rotor and it looked okay, but the back side had a weird wear pattern to it. So I (a couple of hours ago) replaced the rotor and pads and greased it all up thinking a pad had just gotten wedged.

 

Well, I just took the car on a shakedown drive and it drives fine, but when I got back the problem side wheel (left rear) was hotter than the right rear. It was not too hot to touch, but definitely hotter than the other side. Preliminarily, it seems the problem is still there based on the little bit of wear that is visible. Which means the problem maybe the caliper. A new "loaded" caliper (caliper and bracket) from advance is only $100, so I may just do that. If I do that, I may do it very soon so I don't ruin this new rotor and set of pads.

 

What is happening, it appears, is that the bottom part of the pad (part closes to center of rotating assembly) is wearing normally, but the top is not. Here is a pic of the backside of the old rotor and pad. You can see the rust ring on the outer edge of the rotor:

 

 

I think there is a problem with the caliper, I did get both of these from a junkyard a couple of years ago. From the looks of that old rotor it had been doing this for a while, maybe even since I've had the 94+ rears on there (almost 3 years now). Any other thoughts??

 

[slick]

Yeah, looks like a bad caliper to me.

[Brian P]

the slider(s) on the caliper must be sticking, but there's also the possibility the retaining clips aren't aligning the pads right. More than likely the former. I can't remember how I greased them but I think the lower slider I had to swing the caliper off it, and clean it up. The upper one I grabbed with pliers once the caliper was off the bracket, and pulled out. It's been a while since I've done w-body brakes (never thought I'd say that!!)

[slick]

Really though, if you put the pads in the caliper, put it all together, and hit the brakes, shouldn't the pads align themselves properly anyways?

 

 

[Brian P]

I've seen some weird shit happen when a slider is even "kind of" sticky, such as that. I've actually seen OEM crappy GM rotors cause a condition like that, only you see the rotor surface kind of "delaminate" itself on the outer edge. It looks different than the OP pic but the end result is the same.

[Robby1870]

The sliders looked okay when I took it all apart and I made sure to grease them up well when putting the new pads in. Even after putting the new rotor on, just 20min of driving and I can see this same wear pattern starting on the new rotor. And the new pads fit in the sliders fine. As easily as the new pads went into the sliders I can't imagine they are what's causing this.

 

I think I may just buy a new caliper assembly, throw that on, and see how it goes.

[Brian P]

Yeah I can't say for sure what the deal is without looking at it. Is the caliper surface that touches the outer pad damaged or uneven in any way?

 

Also I remember my last brake job, I had to file down one of the outer caliper "ears" that sit in the bracket, since it kept getting hung up. It just had a burr, but it was enough to cause a problem. I guess just be sure where those ears sit, they're smooth, lubed up, and the anti rattle clips are clean and straight.

[5speedz34]

Get new calipers. Junkyard calipers for the loose.

[Robby1870]

Here are a couple more pics. The outer rotor surface just looks uniformly rusted and you can see the angle on the pad. Again, this is all on the inside pad. The outer pad wore just fine.

 

 

 

Now pics of the back of the pad, you can see where the piston touches the back of the pad:

 

 

 

And now the other side of the rotor and its pad

 

 

 

I don't know if any of that helps; I can't get much out of it, but maybe someone can.

 

 

[Crazy K]

if I am looking at it right.... the inside edge of the inner pad is wearing faster?

 

 

and what do you mean the outside looks universally rusted? as in no pad contact???????

[Robby1870]

if I am looking at it right.... the inside edge of the inner pad is wearing faster?

 

 

and what do you mean the outside looks universally rusted? as in no pad contact???????

 

yes and yes

[Crazy K]

WAIT!!! does your car have auxiliary helper springs????????

[Robby1870]

I don't even know what those are.

[Crazy K]

I don't even know what those are.

LOL

 

on the back side of the strut is a rubber helper spring that goes between the strut and the rear lateral link arm. some cars have them.

 

if in doubt take a picture!!!

 

and a picture of the front of the rotor too, please

[Robby1870]

I see nothing of the sort.

 

The last two pics in my post a couple of posts up are of the front of the rotor and its pad.

[5speedz34]

The auxilary spring looks like a big rubber 8. I would get new calipers because junkyard calipers suck.

[BXX]

Yes, that pad wear is due to slider issues

 

 

/thread

 

 

[Crazy K]

i've had some luck with j/y calipers.... but not always.

 

 

time for a new caliper... though i suspect the slides might be a significant culprit

[Robby1870]

Well I just went and bought new sliders. I'll put them on in the next couple of days.

 

If anyone is at Advance trying to find these, look under Brake Hardware - Rear Axle Kit. The name doesn't make a whole lot of sense, but that's where they are.

[Brian P]

Ken, GP's normally didn't get the aux springs, except some LE's.

 

For some reason I thought the outer pad caused the problems . Hows the piston look, and I think the piston needs to be rotated to a certain position for the pad to sit flush onto it? Basically that little, I guess it would be called a locator tab, needs to sit into that recess on the piston face. The recess IIRC was in the shape of a V, allowing some margin of error but not much.

[Robby1870]

Ken, GP's normally didn't get the aux springs, except some LE's.

 

For some reason I thought the outer pad caused the problems . Hows the piston look, and I think the piston needs to be rotated to a certain position for the pad to sit flush onto it? Basically that little, I guess it would be called a locator tab, needs to sit into that recess on the piston face. The recess IIRC was in the shape of a V, allowing some margin of error but not much.

 

Yeah, I know that little locator pin on the pad has to go into the "V" groove on the piston surface. The piston surface looked okay. I'll put the new sliders in and report back. $20 for 4 sliders.....

[Brian P]

ok cool I figured you knew, just putting it out on the table as a possibility

[Crazy K]

Ken, GP's normally didn't get the aux springs, except some LE's.

I've seen a few on GPs...

 

cars that have aux springs that i have seen are:

convertibles (maybe all of them?)

base model cars without a rear swaybar

sporty models with a rear swaybar.

many 3.4 cars... (including a 95 GTP)

 

in fact... everycar i own has them except both my 95s!

 

 

my 91 euro did not have them... so 8/11 Ws that I;ve had had aux springs...

 

granted... those aren't GPs...

[Robby1870]

Little update:

 

So I put new sliders on today, drove it around, still doing the same thing. I reached under there touching things and it definitely is something in the caliper/rotor/pads. I guess at this point all that's left to change is the caliper and bracket. Stupid car....

[White93z34]

I had a similar issue with my 94+ setup, in the end I replaced a caliper, seems to have solved the issue so far.