Brake fluid everywhere, melted piston, zero pad left... only on one side?
 

Ok, so I'm at a bit of a loss here.

2017 BRZ track car. Stock Brembo brakes.

Brakes started to get real soft near the end of the last session on Sunday while my gf was driving (after running both Saturday and Sunday completely trouble-free). She pulled into the paddock thinking the fluid was getting hot and found that fluid was absolutely puking out of the caliper on the driver's side.

We figured the piston seals got toasted, so we got a rebuild kit and pulled the caliper. Found that there was absolutely NO pad left at all and the piston was actually melted to the backing plate of the pad. Rotor looks pretty shredded too. Extra weird because the pads on the passenger side looked totally fine with roughly half life left.

OK... so maybe the seal letting go caused that caliper to get really hot or something and disintegrated the pad. Let's rebuild the caliper.

Then we found the weird thing... the seals inside all look completely fine. Basically indistinguishable from the new seals except they feel a little less stiff if you squeeze them. Except for the front part of one of the pistons being melted... I can't find anything at all that looks or feels wrong with the caliper.

My only thought right now is that somehow the drivers side pads were sticking or wearing unevenly or SOMETHING, which caused the pads to wear out super fast on that side, which caused the backing plate to grind against the rotor and cause a TON of heat, which melted the piston, which caused it to push out beyond the seal and cause the fluid to start coming out everywhere.

But what could have caused that pad to wear so dramatically? Anyone experienced serious uneven pad wear on these brakes before?

Weird. All i can say is make sure the pads due not bind in the caliper. Also when you release the brake pedal the rotor turns freely (like the other side). Freshly machined in spec rotors will even ware and should prevent fluid loss with a pad failure.
Your final symptoms were from the pad failing.

Tracks that are biased one direction or another will often wear the front right or left noticeably more then the other side, more pounding = more heat = more wear, even on the brakes. Catastrophic failure however is surprising, 6 year old car, snow driven? might have just gotten unlucky with a stuck caliper.

or traction control got left on by accident?

Are you referring to ebfd? If so, that needs pedal dance to be turned off, but I would think something would have to go very wrong for it to have that effect.

I have had a caliper not back off after braking on another (commuter) car, but that led to some pretty nasty vibrations at ~75mph. Definitely wore down one side more than the other though. Could have been just one piston assuming the Brembos have more than one?

What direction (clockwise or counter-clockwise) was the track? Was stability control on?

Previous owner of my car had a similar thing happen with his first set of pads. Except it was the AP racing endurance kit, so there was still pad left and the caliper wasn't damaged. But the pads on one side were like half the thickness of the other side (which is like an entire normal pad's thickness difference). I don't think he ever got to the bottom of it.

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-Mike

Sounds like a sticking caliper.

It may not visually look or feel like it, but the evidence would say otherwise.

Do you have a datalog?

Thanks for the responses everyone.


No datalog unfortunately.

Think we just got unlucky? It's weird because, with the pistons out, if you look at the caliper you'd think they were in perfect shape (aside from being a bit of a different color than stock due to heat over the years :)


The track was a pretty small local one, lots more right hand corners than left. Could that really have an impact? I've run this track a lot before and never noticed any unusual wear.

Car is a full track car. It saw a bit of DD duty early in its life, but hasn't seen the street in years. Only about 30k miles but definitely sees hard use on track. Right now it's stripped, caged, supercharged, and prepared for Gridlife's GLTC wheel-to-wheel race series. Traction control is always off via ECUtek. G-Loc r16 pads, DBA 2-piece rotors... even if it was wearing super unevenly... it's pretty weird that it would wear through half or more pad life in a weekend. These pads are usually good to go for quite awhile, especially on the BRZ which isn't typically too hard on pads.

Everything was off anyways.

The Brembos have 4 pistons per front caliper. Only one melted and it appears that one was also the one that had come out far enough to let fluid past the seals. The pad was fully gone though... nothing but the backing plate left.
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I would recommend rebuilding ALL calipers to be safe, and then carry on!

Have you considered any other pads that may have a different effect with heat, or that may give you more indication of overheating? Gloc responds by just disintegrating faster, rather than anything else, with no big feedback for the driver.

Interesting. I've had great luck with them and ran the same compound on my 450whp STi track car without any issues overheating, so never even really considered they'd overheat on this car with 200whp less. My GF has a loose sponsorship arrangement with them, so that does help too :)

If you've had experience with them disintegrating on overheating that is interesting though and might explain why the pad just disappeared.

It's weird to think that it was caused by a pad sticking though as she said she never noticed the car pulling at all. I'd think if it was stuck it would be pretty noticable, but maybe it was just barely dragging?

Can't argue with free pads, but sometimes lost seat time may not be worth free!

You wouldn't feel the sticking pad with Glocs; the loss of friction at very high temps wouldn't manifest as EBD will take care of the rest.