Chriz06

Car is a 07z with 46k miles, and from the looks of the brake calipers it was driven aggressively at some point in its life.


I had replaced all 4 corners with new oem rotors and powerstop z26 pads. I drove around after bedding the brakes and didn’t pay much attention to them after that as the car would brake as it should. Within a few months I had some judder in the steering wheel. I noticed there was significant uneven wear. By this time it was late fall so why not a winter project, I decided to take everything apart and try to figure things out.

what I found was the rear passenger caliper had one piston that was starting to grind down, so I rebuilt all 4 calipers (precautionary) with new pistons/seals. I also found that the rotors had started to warp from glazing.

I just replaced the pads and rotors again after the rebuild, did a full pressure bleed of the entire system with fresh fluid, and the fluid coming out of the rear caliper was black until the fresh stuff came through. Then once all the old fluid was out I flushed the system again, and replaced with motul fluid.

Right now the car is braking better than ever in the 2 years I’ve had it, but I’ve only got about 200 miles on the new pads after bedding them. I have not used the brakes above 80mph yet. What I am concerned about is that it still doesn’t look like the pads are wearing evenly…. Again.

Anyways, I’ve attached the front and rear passenger side rotors to show the significant difference.

The only thing short of replacing the caliper that I can think of is replacing the rubber brake lines with upgraded ss lines since they are original lines (assuming) and since the piston was ground down and the fluid was black I am guessing they used to get hot quite a bit and it’s taken its toll on the oem brake lines.

I can’t imagine what I’m missing here, hopefully somebody has some insight for me to figure this out. Hell, maybe I’m overthinking it, but I’d rather be safe than sorry.

Chris



Front passenger pad wear

Rear passenger pad wear

gsflyer2011

It is your pads that are junk. Replace them with carbotech 1521 monoblocks. Expensive but cheaper in the long run.

AzDave47

I found taper wear typical (single pads and padlets) both from the hub out and also from the rotating direction of the pad with the OEM calipers.I did quite a few track days and pad/rotor wear was only part of the problem, the prime problem was too much heat to the front brakes. By the time I figured that out, the calipers needed both mechanical and cosmetic rebuild. I sold them on the forum and replaced them with Wilwood Aero 6s.

Chriz06

yeah I was looking at the wilwood aero6 fronts and super lite 4s as replacements if I needed to go that route. Did you have any problem with oem rotors or did you upgrade to the 2 piece rotors as well?

this is probably a dumb question, but since it’s not leaking, is there any way to rule out the rubber brake lines as the issue?

Hib Halverson

The pictures you attached are not calipers. They are brake discs and they show the pad material is transferring to the surface of the disc.

I'd switch to a quality brake pad...on cars with iron brake I use Porterfield R4S pads which are a great performance street pad.

Then you need to abrade the brake disc surfaces with some abrasive pads on an air grinder to remove the deposits of pad material. If you're desperate, you could take the brake discs to a brake service shop and have the discs machined just enough to take off that pad material.

Chriz06

thank you for pointing that out, I definitely said I attached pictures of the caliper and meant to say rotors as my concern is the uneven pad wear.

AzDave47

With my stock C6Z brakes I did about 16 track days and consumed lots of pads, rotors and eventually the calipers, excess wear you would never see on the street (1200*F+ rotor temps, 600* caliper temps). Eventually I got enough cooling to the front brakes to make them live.

OEM rotors are fine for the street. I did go thru 2-piece light weight rotors, heavy duty 2-piece rotors, but that was due to the track days. For street use I did Carbotech 1521 pads, partly because the pad material was compatible with their full track pads. They were good street pads, had lower dust than OEM and lasted well on the street.

tommyc6z06

I use those those same Powerstop Z26 dust free pads on street, with the OE holed discs without problem. No pulling, 100% even wear. Quiet, dust free. I really like them. For street.
I swap over to slotted, 2 pc discs and race pads for track use...with plenty of cooling, using grill mounted ducts (thanks AzDave47), as well as ZR1/Z07 deflectors on the front LCAs

But your question is pertaining to street use as I understand it, and I suspect your discs have somehow been contaminated with uneven deposits at this point.
Thats hard to remove if its gone too far. Is the car braking straight now? any pedal pulsations? You can try sanding the discs with some 60 grit to remove the uneven transfer layer....assuming its still just discoloration at this point.
From time to time, even mild street pads need to be used a bit harder to properly clean off the rotor surface...then, of course, not stop right after, or with your foot on the brake pedal to allow them to cool without hot spots under the area that the pads are clamping.
Can't always be piddling around with very light, infrequent brake use...

But, taking a step back, I'm perhaps still not 100% clear in understanding what you are referring to as uneven wear at this point.
The rotors? The pads? Ie inner vs outer? or a specific padlet? Or pad taper? If so, then the rebuild may not be good and you may still have a sticky piston. Sometimes a bore can be rough and need light honing.

Also, after the initial caliper rebuild and bleeding, you should not have seen any dark fluid the 2nd time. Where was that old fluid trapped?. It indicates the brakes weren't bled properly, or fully bled. So that's another question as to why the subsequent bleeding purged so much black fluid...but this may be going off in another direction altogether.

Finally, this has nothing to do with the rubber lines. Either a line is leaking, or its not. The worst that can hypothetically happen is an incrementally softer pedal if/when the brake fluid is very hot...so not in you case.

Good luck and keep us posted

AzDave47

OP, just and FYI if you change the rubber lines. Chevy tightens the flair nut (rubber hose to the hard lines) way too tight at the factory. This makes sure they don't leak, but it also distorts the threads on the flair nuts. If you decide to change to SS lines, when you loosen each flair nut the first time, make sure to run it back in forth to help straighten the threads, Alternatively you could use a thread chaser on the flair nuts.

Many people have had problems with aftermarket SS lines because the flair nut threads did not go smoothly into the new line fitting. I have worked on brake lines a lot, including making new flair ends in hard lines. The C6Z was the first one I had trouble with. Two of the 4 lines mated up OK using a normal amount of effort to tighten the flair nut. The other two weep'd. I tightened both of the weepy ones quite a bit more. One still weep'd. The I tightened the last one far more than I have every tightened a flair nut and it stopped leaking and never leaked again.

I had to replace the front SS lines when I went to the Wilwood Aero6 calipers as those take a pipe fitting out at the caliper, not the banjo type OEM fitting and had no problems installing those two new SS lines.