MaxLTV

I had PCCBs on my dailys for the last 6+ years through PNW winters, and I did not understand what people were talking about when they said PCCBs were difficult/dangerous in cold wet weather. At most, I got slightly reduced braking for the first 5ft-6ft of brake application after driving for a while in the rain/snow, and it was easy to compensate for with just pressing the pedal stronger.

Now, after driving the car through deep snow for 6 hours, my brakes are "cursed" - every time I drive in the wet, brakes barely slow down the car for the first 30ft or more, no matter how hard I press. To make it worse, sometimes one wheel dries up before others and the brakes grab suddenly, violently jerking the car to one side - not something anyone would want to experience when braking in the wet. I had to countersteer a couple of times already. I guess it's some kind of contaminant on the rotors or corrosion on the pads that's causing this. What's very odd is that I never had this before in so many years. I'll see if I can burn or clean this off.

But if your PCCB is acting like this in wet cold weather - the good news is that it's not normal. I had this very car for over two years now, and it just started doing it.

redmonkey928

Thanks for sharing, have the full PCCB on a Cayenne Turbo and they do exactly as you outlined. Squeal and not much stopping power when you back out (if wet/cold), or pull forward for a few feet. But quickly revert back to the normal behavior. Have never used them in consistent snow, so couldnt comment on if that has happened across other setups.

CanAutM3

Like track pads for iron rotors, PCCB rely mainly on transfer friction rather than abrasive friction. For transfer friction to be effective, a layer of transferred pad material needs to be evenly deposited on the rotor.

I am thinking that you might have lost that transfer layer. I suggest you do a pad bedding procedure to get back that transfer layer. Bedding procedures can be found with a simple google search.

PTS-BRG

I think this must be a normal characteristic because I too have had some reduced braking on my PCCB's in cold wet weather. You hit the brakes and the first 1-2 seconds it feels like the brakes aren't catching and then it does. I have also found that a harder press on the pedal gets the car to stop but it is a bit unnerving..

MaxLTV

My point is that I did not have it before, for years, across multiple cars. So this strong effect must be avoidable. Or rather that it was about 1/10 of what it became - from under 1/10 of a second of slightly reduced braking to close to a second of noticeably less braking. I will try to burn it off in the next few weeks, but now that the rain has stopped I'm busy trying to put break-in miles on the RS, which also has PCCBs and does not have this issue. It's definitely some kind of contamination of rotors or a corrosion layer formed on pads. I suspect the latter because it started after driving deep snow with lots of salt for an extended period of time (got caught in the arctic blast in the mountains).