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?






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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.



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


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[RussMcB]

Originally Posted by Weeberone

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]

Originally Posted by RussMcB

Yes, I have seen this many times.

From just "normal" use?

[Dynomite]

Originally Posted by Weeberone

From just "normal" use?

Great Question
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

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

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

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

Post 233 - Installation of Wilwood Rotors and C4 to C5-Z06 Conversion

[Weeberone]

Originally Posted by Dynomite

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-...-wear-unevenly

https://www.quora.com/Why-do-BMW-bra...e-same-caliper

[Dynomite]

Originally Posted by Weeberone

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

https://www.quora.com/Why-do-BMW-bra...e-same-caliper

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

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

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.

Originally Posted by Weeberone

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)

Originally Posted by Weeberone

Leading in respect to rotor rotation.

Got it...... Or.....That part of the Pad that the Rotor sees first (Unless you are in Reverse)

[Weeberone]

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





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.





Here’s what drained out of the Caliper upon removal. No wonder the fluid didn’t take heat well.

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.



One down. Three to go!




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