Uneven brake pad wear

[Weeberone]

Anyone see brake pad wear like this? Is this normal, or just a result of a fun track day on decidedly street pads?

https://uploads.tapatalk-cdn.com/20190125/33b1d237a2908d1940ae3f08f1999b41.jpg

https://uploads.tapatalk-cdn.com/20190125/9150f07877c15bc21dbde3e0a05196e7.jpg


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[Weeberone]

The top pic is passenger side and bottom pic is driver side. On both calipers the leading end of pad is more worn. I've done some reading and apparently this can happen in multi piston calipers when the pistons are the same size front to back.

the pistons moved freely back in the caliper, so I know they're not stuck. None the less they are getting new seals and lines and fluid. I'm sure there were other factors involved like old fliud etc.

These pads endured a gruelling track day that left little piles of pad debris on the wheel rim after each session and were getting eaten up quickly, no doubt amplifying any weakness in the system.

[Weeberone]

These are what is going in next.

https://uploads.tapatalk-cdn.com/20190125/3dd70729762eb265165060b6b243a8cf.jpg

Some EBC Yellow stuff pads and new EBC rotors. And stainless braided lines, of course.


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[RussMcB]

On both calipers the leading end of pad is more worn. I've done some reading and apparently this can happen in multi piston calipers when the pistons are the same size front to back.Yes, I have seen this many times.

[Weeberone]

Yes, I have seen this many times.

From just "normal" use?

[Dynomite]

From just "normal" use?
:happy1:


Great Question :cheers:
I have never seen this before on my Zs, trucks or other cars.
But then again my Zs, trucks, or other cars have not seen a grueling track day :p

The Leading End of Pad is the part of the Pad that grips the Rotor first (toward the Rear of the Car) unless you are in Reverse :p

Since both left and right Calipers suffer the same issue (I cannot find this issue in a google search), the normal analysis of the Calipers issues is not applicable simply because the odds of both suffering the same issue at the same time is remote. That indicates it is a driver or driving (grueling track day) issue which is very interesting and would prove that taking stock calipers and rotors on grueling track days is not recommended :D

One other possibility does exist......both left and right Calipers and pads were installed the same incorrect way :p

Post 233 - Installation of Wilwood Rotors and C4 to C5-Z06 Conversion (https://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-12.html#post1590759175)

[Weeberone]

From your description it appears that the "following end of the pad" and NOT the leading end of pad is more worn?

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Leading in respect to rotor rotation.

[Weeberone]

https://www.quora.com/What-causes-a-brake-pad-to-wear-unevenly

https://www.quora.com/Why-do-BMW-brake-calipers-have-multiple-pistons-that-are-different-sizes-in-the-same-caliper

[Dynomite]

https://www.quora.com/What-causes-a-brake-pad-to-wear-unevenly

https://www.quora.com/Why-do-BMW-brake-calipers-have-multiple-pistons-that-are-different-sizes-in-the-same-caliper

Thanks for Posting this Thread......Learn something New Every Day :thumbsup:

Nice find ……….makes sense but still not explained why that is not an issue before now as far as I can tell for "normal driving" except for the "grueling track day" which would suggest that Stock Calipers and pads are not good enough for a grueling track day :cheers:

It appears to me the front piston on your Calipers is larger in diameter.
Which would be the GM Design Correction for that Moment Issue as your BMW Link suggests.

My analysis would be that on a "grueling track day" as the rotor heats up (much hotter than during normal driving) the frictional forces increase such that the compensatory larger Cylinder pressure does not compensate for the increased Moment on the brake pad which causes greater pressure on the rotor on the Leading End of the Brake Pads. Different material Pads or Calipers built with greater compensation would be required.

You are NOT changing Calipers??

Seems to be a Caliper/Brake Pad Temperature Issue related to your driving conditions "grueling track day".

So....Why is the GM Design Correction not working....seems it is because of "grueling track day" probably associated with Pad Material Selection related to the much greater Rotor Temperatures.


These pads left little piles of pad debris on the wheel rim after each session and were getting eaten up quickly.

You now got me checking ALL my Brake Pads (including Wilwood C5 Z06 Calipers)
The C5 Z06 Calipers have the larger piston on the Following end (Toward Front of Car) of Caliper.
This be a Drivers Side C5 Z06 Caliper (Note the larger diameter Cylinder and Piston on right side in first photo) :cheers:

https://cimg4.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/600x450-1/80-8c08e4b2_83a5_4ff1_ae3c_f9413d345d0e_2329_00000366 15e90410_zpse864dc35_1__4b80b6b5a054aaee8eed7e9b9c e795f90f8a627e.jpghttps://cimg6.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/400x450-1/80-2f8f7c4e_edcf_4651_944d_affb7f12e766_1__b2f4b5bbc1 3976a4bee934af3cdd34f9254984c8.jpg

Leading in respect to rotor rotation.
Got it......:) Or.....That part of the Pad that the Rotor sees first (Unless you are in Reverse)

:thumbsup:

[Weeberone]

Ok. I rebuilt the passenger Caliper. Here’s a before and after.

https://uploads.tapatalk-cdn.com/20190128/4f118a8e727b73af7bb9b986709f0f54.jpg

https://uploads.tapatalk-cdn.com/20190128/440f8179d6a53729f565a8022ff1366a.jpg

The pistons looked good with no damage. They came out of the bores easily with compressed air. Note that both pistons are the same size.

https://uploads.tapatalk-cdn.com/20190128/b0873621746001ad11ee8880c4a6d472.jpg

https://uploads.tapatalk-cdn.com/20190128/b0fc345d4df8613eaf93ac98ce2b807d.jpg

Here’s what drained out of the Caliper upon removal. No wonder the fluid didn’t take heat well. https://uploads.tapatalk-cdn.com/20190128/7601876771b9dc1fe341811ac5e9d9cb.jpg

Fresh new fluid to replace this brown stuff. I’m using Motul RBF 600. The old is gross. Interesting to note that I flushed the system only a few months ago and the fluid was clear and changed to this colour after my track day.

https://uploads.tapatalk-cdn.com/20190128/a765e0118556e30fc244b7d48a9c6b25.jpg

One down. Three to go!

https://uploads.tapatalk-cdn.com/20190128/df44cdf027f013bb5cdde20f4357f50c.jpg


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[Weeberone]

I started the back brakes. Interesting that these pads show a taper too, even though the rear is single piston. It’s just barely visible.

https://uploads.tapatalk-cdn.com/20190128/c7909eac45b48f9554efb139a5bf672b.jpg

The top in this picture is the leading edge.

These pads look just destroyed. Anyone thinking about buying Raybestes pads. I suggest don’t.

https://uploads.tapatalk-cdn.com/20190128/59b67f10b2851c21de08d706e7210af2.jpg


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[Weeberone]

Here’s a shot of my front wheel the day after.

https://uploads.tapatalk-cdn.com/20190128/7380a2f7c16104beccf9bc732bda3d4d.jpg


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[Dynomite]

https://uploads.tapatalk-cdn.com/20190128/4f118a8e727b73af7bb9b986709f0f54.jpg

Note that both pistons are the same size.


Nice Photos and thanks for Posting :thumbsup:

That is MOST Interesting that both Pistons In the Stock Dual Piston Front Capliper are the Same Size :icon_scra

That would then explain the issue as you found in the BMW link related to the Moment requiring a larger Following Piston as a Remedy. I checked my C5 Z06 Calipers and the Following Piston is Larger Diameter :handshak:

https://cimg4.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/800x500-1/80-s_l1600_1__bca4e2923fd57d337e25ccecf6d00f6fd681cfa a.jpg

WOW :thumbsup:
Another Reason to Convert to C5 Z06 Calipers.

Post 233 - Installation of Wilwood Rotors and C4 to C5-Z06 Conversion (https://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-12.html#post1590759175)