P3D front pads uneven wear after track

[destructure00]

Trying to diagnose and fix spongy brake pedal after a track day and found this. This isn't normal, is it? What would cause this?

This is the front passenger side.

Outer pad on left, inner on right in photo below.

 

[beastmode13]

It is normal to have slightly more wear on the leading edge, where rotor enters the caliper. To counter this, some clipers have different sized pistons, with smaller piston in the leading side to apply lower pressure, while having larger piston in the back to apply more pressure.

 

[destructure00]

Driver side

 

[destructure00]

It is normal to have slightly more wear on the leading edge, where rotor enters the caliper. To counter this, some clipers have different sized pistons, with smaller piston in the leading side to apply lower pressure, while having larger piston in the back to apply more pressure.

That makes sense. Is this more than "slightly" though? Or maybe just exacerbated by soft stock pads?

 

[beastmode13]

I recall on my previous track car, I would rotate the pads on the caliper to help even out the wear after couple of track days. I think your prognosis of soft pad exacerbate the uneven wear is spot on.

 

[destructure00]

I swapped inside to outside and vice versa on both sides and put some caliper grease on the slide pins and return springs. Might not need it but they were dry and I figure it couldn't hurt.

Also bled the brakes again, got a couple small bubbles out on both front sides. Rears seemed fine. Brakes are still spongy, maybe marginally better but it could be in my head too. Only thing that's different now from before the track outing is the pad wear.

 

[alexGS]

I swapped inside to outside and vice versa on both sides and put some caliper grease on the slide pins and return springs. Might not need it but they were dry and I figure it couldn't hurt.

Also bled the brakes again, got a couple small bubbles out on both front sides. Rears seemed fine. Brakes are still spongy, maybe marginally better but it could be in my head too. Only thing that's different now from before the track outing is the pad wear.

I was wondering whether air in the caliper might reduce the force exerted by the upper piston (compared to the lower piston) but it does seem clutching at straws. I think you need harder pads. I remember years ago fitting Mintex race pads and being told “they won’t work on the street, won’t work until warmed up” but in my actual experience, they were absolutely fine.

-Alex

 

[beastmode13]

I swapped inside to outside and vice versa on both sides and put some caliper grease on the slide pins and return springs. Might not need it but they were dry and I figure it couldn't hurt.

Also bled the brakes again, got a couple small bubbles out on both front sides. Rears seemed fine. Brakes are still spongy, maybe marginally better but it could be in my head too. Only thing that's different now from before the track outing is the pad wear.

What is your method for bleeding, and how much do you bleed?

 

[beastmode13]

I was wondering whether air in the caliper might reduce the force exerted by the upper piston (compared to the lower piston) but it does seem clutching at straws. I think you need harder pads. I remember years ago fitting Mintex race pads and being told “they won’t work on the street, won’t work until warmed up” but in my actual experience, they were absolutely fine.

-Alex

Most likely not. All the piston chambers are linked so the pressure is equalized in all chambers of the caliper then the entire brake system.

 

[destructure00]

What is your method for bleeding, and how much do you bleed?

Order is right rear, left rear, right front outer, right front inner, left front outer, left front inner.

I'm using the Motive power bleeder, with fluid pressurized to 15 psi. When I swapped from stock fluid I ran 1L through, then waited a few days, engaged the ABS a few times, and ran a second liter through. When I bled this morning, I probably used half a liter. Cracked the valve and let it flow for 15-20 seconds and shut it. Went through about half a Motive catch bottle worth between all 4 corners.

Is there anything I should be doing differently?

 

[beastmode13]

Order is right rear, left rear, right front outer, right front inner, left front outer, left front inner.

I'm using the Motive power bleeder, with fluid pressurized to 15 psi. When I swapped from stock fluid I ran 1L through, then waited a few days, engaged the ABS a few times, and ran a second liter through. When I bled this morning, I probably used half a liter. Cracked the valve and let it flow for 15-20 seconds and shut it. Went through about half a Motive catch bottle worth between all 4 corners.

Is there anything I should be doing differently?

Your procedure and setup is just like mine. With the exception of volume.

When my brake is mushed. I would use an entire quart/liter of ATE Super Blue to purge out all the old fluids. Once brake fluid container is opened, it is exposed to moisture in the air, no point in storing them, so might as well use it when it is fresh. Then use the desired fluid (Motul or Castro) to purge out the ATE, again I would use up the entire container once it’s opened.

 

[destructure00]

I need to find some of the super blue and do that, wasn't sure when I had the stock fluid flushed. Thanks!

 

[Nocturnal]

Isn't this a crazy amount of wear for just one track day? I had 2 days on my stock pads and couldn't see much wear prior to replacing them. (I believe they were glazed, super squeaky and grindy)

 

[jyalpert]

Yeah a little unevenness is normal but that looks kinda excessive, especially with the cracked pad there. What brake pads are those?

I need to find some of the super blue and do that, wasn't sure when I had the stock fluid flushed. Thanks!

FYI, they don't sell Super Blue anymore. It was great; you used to be able to tell when the old fluid was out and the new fluid was in, because it would change from blue to gold. But apparently it's illegal for brake fluid to be blue, so they stopped making it.

Anyway that procedure sounds fine. If you think it's not working, you can do the ChrisFix "one man bleeder" method which you can find on YouTube.

 

[destructure00]

Yeah a little unevenness is normal but that looks kinda excessive, especially with the cracked pad there. What brake pads are those?


FYI, they don't sell Super Blue anymore. It was great; you used to be able to tell when the old fluid was out and the new fluid was in, because it would change from blue to gold. But apparently it's illegal for brake fluid to be blue, so they stopped making it.

Anyway that procedure sounds fine. If you think it's not working, you can do the ChrisFix "one man bleeder" method which you can find on YouTube.

Those are the stock performance front pads. I have RB XT910s on order to replace them.

Thanks for the info, I'll look up that video.

 

[mcbarnet007]

The sponge feeling is from the cracked pad. The pad is not solid anymore and will compress more. Don't do threshold breaking on the track with the stock pads because it cannot handle that amount of heat. The UPP sport brake pads did not crack and wore down more evenly than the stock.

 

[destructure00]

Pedal feel has come back a little bit. I sanded the glazing off the pads and swapped inside for outside on each caliper. I think they are wearing back into the rotors again and getting a bit better. Still going to replace them as soon as the RB pads arrive.

 

[destructure00]

Got back from vacation to a nice surprise from @EVTuning!

Rear pads are on the way too, only thing left is the rear rotors. I'll know what I'll be doing tomorrow morning

 

[destructure00]

Got the fronts done this morning. The hat on the RB rotor is about 3mm thicker than stock, so it hides the lip around the hub. May or may not be useful info for anyone dealing with wheel fitment issues.

Brake pedal feel is back to nice and firm with new pads on front. Curious to see what the rears look like when I swap them out too.

After bedding

 

[N54TT]

Got the fronts done this morning. The hat on the RB rotor is about 3mm thicker than stock, so it hides the lip around the hub. May or may not be useful info for anyone dealing with wheel fitment issues.

Brake pedal feel is back to nice and firm with new pads on front. Curious to see what the rears look like when I swap them out too.

View attachment 422059

View attachment 422058

After bedding
View attachment 422057

Nice!! It’s probably closer to 5mm thicker. Looks to be about 2mm further out than the 3mm lip that’s present with stock rotors.