I'm frustrated here after doing a brake job on my 85, maybe you guys have an idea I haven't thought of yet.

New rear rotors (EBC)
New rear pads (Hawk blue, track compound)
New rear hoses (Russell SS)
Reman rear calipers (Centric) with new pins and pistons.
Adjusted parking brake
Also new front pads, cleaned pistons, new bleeders, fluid flush of course.


The pads were not dragging before this. I did all this simply because the rear rotors were worn past the minimum thickness, and the calipers were corroded and about frozen on one side, I think causing the pedal to feel sticky when really pushing on it.


The rotors came fully painted, but I figured I'd let the pads burn it off.

I'm getting a ton of dust on the left rear wheel, audible noise while driving from that corner at least, and the rotor is wearing, yet the inner part of the swept area hasn't even burned the paint off! That was my first sign.

I pulled the pads off that side and they're already tapered as if it's a spread caliper out of the box. I measured though, and it seems flat. The taper is very visible but only measures a few hundredths. The previous pads had taper also, even on the front wilwoods, but I figured it was just from hard braking at the track. Also the Hawk inner pad is thinner than the outer, although they weren't even out of the box, which I think is bizzare. Seems to be a lot of wear considering I've only driven it about 6 times since doing the work, albeit trying to do hard braking where I can. I didn't even attempt to bed the pads yet because of the odd initial wear.

Engaging the parking brake slightly more doesn't change the noise, so I doubt that's it.

There were no issues during install with anything fitting. That particular caliper was an 84 application btw, but it's the exact same caliper as 85 according to GM's parts book, it just came with a different bracket. (They didn't have the bare LR 85 caliper in stock)

I guess I can keep driving it until it finally starts contacting the inner surface of the rotor and see how bad the taper is.

Even if nothing lined up, it shouldn't drag. The pads are also very aggressive, but they didn't drag before. What prevents the from dragging normally? Do the pistons retract a little when you release the pedal?

During bleeding I had to be careful not to get squirts from the reservoir, but that tells me the port is open fine.


I honestly don't remember if both reservoirs squirted though. (85 has separate front/rear reservoirs) I suppose it's possible for the front port to open, but not the rear? I did not adjust anything there, maybe something moved during bleeding, I could feel in the pedal the valve being exercised when bleeding the brakes, Such as when you bleed the rear while the front is done. I don't remember how that's supposed to feel, but it was a little sticky at the end of travel.

Or does spring steel corrode in brake fluid? I used a different bias spring years ago and haven't checked it since, maybe the whole combination valve is corroded to hell. Are the DRM springs different material or something? I figured all the springs had to be pretty similar in metallurgy, I believe stainless for example is too weak to use for springs. I didn't use the DRM because it was too weak to correct my bias with the large front brakes.

Maybe I overfilled the reservoir during refill and the cap is exerting some tiny pressure on the fluid?



I have more time to ponder stuff than I do to wrench apparently. I just figured it'd be an easy job. I know there are 93 things that can go wrong, but damn it worked pretty good before I touched it. WWCGD?

Disc brakes do not retract like drum brakes. There is always a slight amount of drag on the rotors, where drum shoes get pulled away by springs. The magic word here is slight.

Are you sure the park brake is not too tight?
Was there a good stream of fluid from each line/fitting when bleeding?


Joel

I had this problem on my my car and found that I had not put the clips on that hold the pads in there should be 2 spring clips on each pad I only had 1 on each . might not be your problem but thought to share what mine was .

I have no spring clips. Where would these go? The pads have a spring attached to the outer edge that helps keep it floating away from the caliper, actually kinda jamming it into the bracket. There's also an H shaped piece that goes into the caliper middle, that this spring can slide on easily.

I've used various rear pads a few times before without issue. This is the first time I've used the H shaped pieces.

I've had a pair of pads hang up a little when I used an aftermarket (but good quality) set. No matter what I did, they rubbed a little bit. I eventually gave up and figured they'd wear in. I assumed the pads were just slightly thicker than stock measurements.

Well I'm pretty sure I fixed it. Ill drive it more tomorrow and keep an ir gun handy to be sure before I count my chickens.

A combination of things, but something that could affect anyone with floating calipers potentially.

the rears float, so if the pins are out of whack or are dirty... yea, all bets are off!

Check the grooves they ride in

Pins are new and lubed, brackets is reman on one side, original on the other. The pin slop feels fine. Hydraulics all checked out.


Here's what was happening:

I added those H clips when I installed the calipers. Plus the caliper on the driver side is powdercoated. I guess they powdercoat their loaded calipers as an upgrade. I spray painted the bare caliper I bought to match it. The H clip goes in the middle of the caliper where the pad springs push against. Those springs are to keep the pad pushed against the bracket. Problem is, when you powdercoat the caliper there, then add the thickness of the H clip, it compresses those pad springs even more, jamming them hard into the bracket. This force tries to pull the caliper away from the axle, taking up whatever slop the pins offer. All this proceeds to misalign and bind up the caliper. On top of that, the bracket wears where the pad backing plate pushes on it. This wears divots, further hindering free movement. AND, the H clip is very smooth, so the back end of the pad slips around quite freely. All this means the ID of the outer pad never gets pulled into the rotor face. Both pads were wearing at an angle. You can see this effect when you loosen the caliper bolts, and the pads try to push it all away from the rotor.

I removed the H clip to relieve some of the spring force, and also filed the bracket contact surface smooth. This side I used an original bracket, and had painted it, so the paint piled on probably made that surface even worse.

Now if you're thinking the hydraulic pressure will overcome all that and square it up, well it did somewhat, but the full pad still never touched the rotor until I fixed this.

And, when you release the pedal, the caliper floats and tweaks back away from the rotor, and that outer edge of the pad then starts dragging on the rotor. The race pad compounds are probably really aggressive and just with that light drag were able to wear the outer edge of the the rotor surface.