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]

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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[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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[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.



The top in this picture is the leading edge.

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




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[Weeberone]

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




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[Dynomite]

Originally Posted by Weeberone

Note that both pistons are the same size.

Nice Photos and thanks for Posting

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

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



WOW
Another Reason to Convert to C5 Z06 Calipers.

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

[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.

[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.