TurboDog958.2

Rennlist friends,

I recently purchased a 2016 Cayenne Turbo S with PCCBs. I got a phenomenal deal on it, and she’s practically flawless except for some very annoying judder coming through the front brakes. It’s had a full PPI, brand new tires and fresh alignment performed by GMP Performance in Mooresville NC. The front suspension appears to be in excellent condition, with no signs of wear or cracking of bushings, etc. It just turned 100K miles.

I also just put brand new OE pads on the front, with new hardware clips, bolts, etc. While it was apart, I thoroughly cleaned the rotors; I cleaned every cooling hole and chemically cleaned the rotor surface with liberal amounts of Brakleen and gentle use a fine Scotch Brite pad. There were some visible deposits on the inboard rotor face which were removed. I also closely inspected all the hat-to-ring attachment hardware which looked fine. The rotors looked virtually perfect when I reinstalled them. I was excited when I first bedded the pads as it seemed to have corrected the judder issue, but to my dismay, over the next week it returned.

I don’t believe that PCCBs can “warp”. I have not had the opportunity to check for runout, but assuming the disc is flat and given the floating nature of the hat / ring attachment, I don’t think that runout could be the issue. (Correct me if I’m wrong). My theory was that there was/is an uneven transfer layer of friction on the rotor surface, which is what I attempted to correct with the aforementioned cleaning. FYI I’ve been in the brake business my entire career, having worked for Bendix, Centric / Stop Tech, PFC, and now I own my own commercial vehicle brake parts company. Not at all bragging, but just prefacing that I’m fairly knowledgeable on the topic of friction, brakes and braking technology. That said, I have very little experience working with PCCBs, so this is what I’m looking for help on.
So...the twelve-thousand-dollar question is...has anyone experienced this and successfully corrected it?

RAudi Driver

Customers and dealership personnel must be advised to NEVER ALLOW WHEEL CLEANER, TIRE CLEANER, or BRAKE CLEANER TO CONTACT THE ROTORS. Ceramic rotors will absorb any material that comes in contact with them. Only soap and water should be used to clean wheels and tires. Any product that is applied to the rotor surface will cause damage to the surface and is not covered under the warranty.

TurboDog958.2

Well, isn't that just great. So much for my vast knowledge of brakes. So now I wonder if there's a remedy to that as well, or if I only made matters worse and am one step closer to investing in new rotors. They look so damn good though...it seems crazy to need to replace them.

This was what I thought might be the culprit causing the judder; uneven deposits on the rotor face.

This is how pretty they looked when reinstalled. I wonder what damage, if at all, the Brakleen may have caused.

NKCowboy

What is judder? Just an annoying vibration or is there a safety issue?

I read that the Porsche top brass does 10 consecutive panic stops from 80% of maximum speed before they approve a model's brakes. If you can find a safe place to do it, maybe take that CTTS up to 145mph 10 times and slam on those babies. It just might work, perhaps by vaporising the Brakleen?

I love those PCCBs. The callipers are so big it makes the car look like it got a "Denver boot" every time its parked. They looks particularly good with a body painted blue.

TurboDog958.2

You have the general idea correct. It's that annoying pulsation that you can feel through your steering wheel when you apply the brakes. Interestingly, very light applications and / or very heavy brake applications don't seem to be too bad, it's the moderate (and most common) brake applications where it wants to shake the damn steering wheel out of my hands. (Not THAT bad but plenty annoying.)

I've heard of the remedy you described, and I've performed milder versions of it. Maybe I'm being too wimpy and really need to bring it up to hyperspeed and stomp on it harder. Worth a try, I guess.

RAudi Driver

Don't bed those brakes. I'm wondering if that white mark that you cleaned off, but can still see something in the rotor or missing from the rotor, is causing that.

TurboDog958.2

Curious why you recommend against the re-burnish? I've seen that recommended for PCCBs from multiple sources.

I'm reaching out to a brake guru I know from the industry tomorrow to see what he has to say. The pulsation is markedly less when the brakes are cold, which reinforces my theory that it's not runout, but I feel that at some point I need to get them on a lathe with a dial indicator to confirm that. I need to exhaust every possibility before I bend over and buy new rotors.

It's particularly frustrating since I recently bought my wife a 2018 Macan S and the brakes on that are absolutely smooth as silk. Grrr

RAudi Driver

I'm not an expert on PCCB's but I have a set and I take great car to make sure they last as I'm not into shelling out that type of money to get them replaced. Bed them if you wish but I'm not recommending that. If you ahve a shudder, a simple bedding will not work, especially if you're already cleaned off all the foreign material with brake cleaner.

When was the last time you did a brake flush? I would put that on the list also.

Also, did you double and triple check that you purchased PCCB pads?

Just brainstorming here with you.

Radi

Same here on 2014 CTT with PCCB, 110k.miles,
new pads from Porsche dealer don’t solve the problem. At speeds over 60 mph when touch the brake pedal I feel vibration on the steering wheel. Hard pressure stops perfectly. I chose to live with it.

TurboDog958.2

Yep, they were identical to the ones I took off, got them from Suncoast Porsche. I was surprised how little friction material came on the new pads; the ones I removed were almost the same thickness. Fluid was flushed about a year ago according to the service records. I've spoken with several tuners who prepare cars for the track, and they all say that the high-speed burnish is worth a shot, and it won't hurt anything. It's cost effective too (as long as I don't get busted, LOL).

As for now that may be my only choice, but I'm going to continue my quest to find a cure. :-)

Gus B.

Maybe these folks can lend a hand: https://www.redisc.si/en/

Here is a thread with some PCCB info that may help you in the future: https://rennlist.com/forums/cayenne-...-and-tear.html

zygomatic

If you're feeling it through the steering wheel, it's definitely worth checking the control arm bushings, just to make sure it's not wear-and-tear on there that's causing your problem. I know that at 100K miles they could very well be at or near end-of-life.

Whitegalaxie

I would go a step further and check all of the bushings and ball joints on the front end. Many are toast at 100k miles or less

TurboDog958.2

Yep, we checked that box - twice actually. The first was during the PPI and the most recent time was when it was in for alignment just a week ago. Everything looks to be in remarkably good condition. My experience has been that control arm bushing failure is more a function of age vs. miles. But, like I said, they appear to be good. I kind of wish they were bad, then I'd have a smoking gun...no such luck.

Similar to Radi's experience, the judder is almost non-existent during very light or hard braking, but "normal" moderate brake applications (80% of the time) are when it happens. Overall, the car stops fine, so there are no safety concerns, it just drives me nuts - especially being a brake guy.

I still need to do the rear brake job, but given that the feel comes through the steering wheel I don't have any expectations that it will solve the issue. But I have the parts, so I'm going to do them. This time I'll steer clear of using Brakleen on the rotors!

Whitegalaxie

The mounting face of the hats don't look great, I would clean them off and also the mating surface on the spindle. If that does not work, I would do several high speed stops and see what happens.