Determining Carbon Ceramic Brake Disc Wear

[Gus Berges]

I know most of this site is dedicated to older 911s so this may not apply to the vast majority of users, but the information found on a multitude of different subjects on this Off Topic forum never ceases to amaze me, so I've decided to share the following information I've put together:

Checking for wear on carbon ceramic brake (CCB) discs:

This will depend on whether or not the rotor hub/hats have Proceq markings (three of them) or not. If the hub of the brake disc does in fact have the Proceq markings on it, then it’s very simple procedure to determine brake disc wear, assuming that you have access to the Carboteq measuring tool from Proceq (known as the VAS6813 in the Porsche world). Since Proceq started to be commercially available in 2014, odds are that carbon ceramic discs manufactured before 2014 will not have the Proceq markings on the hubs. This video is self-explanatory on what the markings look like and how to take the measurements: https://youtu.be/asnGXOmQsYU

If you own a disc that does not have the Proceq markings on the rotor hubs, then determining carbon ceramic brake (CCB) disc wear follows a separate procedure on estimating what percentage of wear has taken place. The following steps yield a much more imprecise result, but it’s better than taking a leap of faith regarding purchasing a vehicle with used carbon ceramic discs. First you will need to understand the information stamped on the brake disc hub (assuming it’s different from the one shown in the video posted above):




Step 1- visually inspect the discs to find the three wear indicators (on each side of the disc). These round indicators (approximately 2 cm. or 3/4”) are spaced 120° from each other. When the discs have relatively little use, these can be at times hard to see unless you shine a bright light on them. If these wear indicators have a different color and can be easily seen, this means your disc is approximately 50% used. If these wear indicators can be seen, then you need to proceed to Step 2.




Step 2- measure thickness of the brake disc. You will need a very accurate micrometer / digital caliper for this. The minimum thickness will be stamped on the brake disc hub (each disc could have a different amount printed on its hub). If the obtained result equals minimum thickness plus 0.2mm measurement stamped on the hub, then you need to proceed to Step 3.



Step 3- weigh the brake disc. The original weight of the disc will be stamped on the brake disc (it could vary per disc on the same vehicle). The scale used to measure the disc must have the ability to measure ± 1 gram and the range that it needs to be able to weigh must be between 0 and 12 kilograms. Each manufacturer will have the maximum allowable weight loss for each disc indicated in their service manual.

Other miscellaneous information: it is normal to have what appear to be micro cracks/fractures all over the disc, even when new, even on the cooling duct cross-members. What is not normal is to have cracks from the hub to the braking surface of the disc (requires immediate replacement). Also not normal is that the braking surface presents multiple areas where the surface seems to have chipped off. It is also not normal, and requires immediate replacement, are chips on the edge border of the disc. To say that carbon discs are a “lifetime part” is simply not true. Based on use, the “lifetime” will vary greatly from one owner to another (assuming same vehicle). If to this we add that each vehicle will have different wear characteristics, then determining expected usage left becomes even more complicated, but by following the steps listed above, one can have a better guess. To say that discs have X more time left or Y more miles left in them is a completely absurd statement to make as there is no way to determine this as there are too many variables to consider.

I am not a mechanic nor pretend to be one. I am currently going through a purchase process for a 2011 Cayenne Turbo equipped with PCCB brakes and knowing that brake disc replacement can easily cost $28K, I wanted to dig deeper into this. All of the information provided above is the summary of days of research among various well known automotive related web boards such as this one, but truthfully said, if it were not for the clarifications and technical documentation (my source for images used) obtained from Maja Bašelj from ReDisc, I would have not been completely sure of what I’ve posted above. My hope is that this information will be of help to others in similar situation in the future and they can find a place where they can find all of the information they need to make an educated decision.

[GH85Carrera]

Not a problem I can ever imagine needing to worry about. It is cool trivia information however.

[bleucamaro]

If I were buying that car, I'd immediately swap the brakes to steel, box the PCCBs, and re-fit them when I sell it.

[aschen]

carbon ceramic brake wear, DIY Bugatti oil changes, and effectively styling my hair are three skills i shall never need in life unfortunately

[sc_rufctr]

Interesting info. Weighing worn disks seems a bit excessive (They'd have to be thoroughly cleaned of all foreign material/carbon/dust etc.).

You'd think accurately measuring their thickness would be close enough.

Originally Posted by bleucamaro

If I were buying that car, I'd immediately swap the brakes to steel, box the PCCBs, and re-fit them when I sell it.

Or give them to the new owner in their boxes.

[GH85Carrera]

Originally Posted by aschen

carbon ceramic brake wear, DIY Bugatti oil changes, and effectively styling my hair are three skills i shall never need in life unfortunately

I agree. Add to the list: sewing my own clothes.

[herr_oberst]

Originally Posted by aschen

carbon ceramic brake wear, DIY Bugatti oil changes, and effectively styling my hair are three skills i shall never need in life unfortunately

I'll add to that, diving off a high cliff with a large, fixed-blade knife in my teeth. Glen, I WISH I knew how to sew. That would be a very handy skill to have.

[Gus Berges]

All joking aside, maybe someday someone who is interested in knowing more about PCCB/ ceramic discs can find this post and may be of help to them and avoid making a very expensive mistake, or at least go into it knowing how to properly gauge the wear and tear on used ceramic rotors.

Regading the comment about weighing it, I agree and this is further clarified on the video I linked. When minute differences make a big difference, it's very concerning how anything can have a huge impact on the final results. I'm guessing that precisely because of this is why Proceq came up with that tool.

Switching to steel brakes is an additional expense that I'll never recoup when I sell it later on. Still on the fence as the ONLY thing preventing me from purchasing this specific vehicle is the fact that it has PCCBs on it (with yet to know % of wear on them that will be soon coming forth on the PPI results). Local market prices are weird in the sense that more expensive options (brakes, engines, models, etc.) usually end up selling for very similar prices to base models due to the fact that they are that much more expensive to run and maintain. Of course there are exceptions to this rule, but you'd be amazed as to how often it happens.

[911boost]

You can drive a loooooong time on PCCB’s when the wear indicators are showing. Unless you are going to track it and really heat them up.

What is more important is the condition of the rotor, cracking, flaking, etc.

There are an absolute ton of threads on this subject on Rennlist.

I have a set of like new rotors for my 911 boxed up in a crate in the basement. The ones on my car have seen track time and for street driving they are still fine.

Good post though.

[Gus Berges]

Yup tons of variables when it comes to these PCCBs. The 997 crowd often change them to iron rotors due to cost (mostly tracked cars). Others swear no use in 60K+ miles. Then others do say that on Cayennes, they are expecting to last 100K miles (not lifetime). Others have only gotten 75K miles. A lot has to do with how they are used and what vehicle is equipped with them.

Cayenne I'm considering has ±58K miles and the wear indicators are visible thus it potentially will need replacing at ±75K miles as other Cayenne users have reported (lots of hilly terrain and traffic being the norm, not cruising all day in a straight line like most US highways). In order to get a better idea if in fact I'll need to replace them at the ±75K mile mark, I decided to learn about the subject matter and decided to share with others as reference material. The information I provided will help others try and get a better idea of where they stand with regards to the wear on used CCBs.

[Bill Douglas]

Originally Posted by sc_rufctr

Or give them to the new owner in their boxes.

Or refit them to the car so you can advertise it as still having the original brakes in perfect condition.

[GH85Carrera]

Originally Posted by herr_oberst

I'll add to that, diving off a high cliff with a large, fixed-blade knife in my teeth. Glen, I WISH I knew how to sew. That would be a very handy skill to have.

My wife grew up sewing. She did not get a "store bought" dress until she went to the high school prom as a senior. She can sew like a pro. She still has a very nice sewing machine, and she uses it to mend things, but she is never going to make clothes again, except knitted sweaters or hats.

As I mentioned in my first reply, it is a cool bit of trivia to have seen.

One of my friends bought a 2021 911 Turbo S with the fancy brakes. His wife will not ride with him because the brakes sequel "worse that her old Pinto from high school days"

I told him I would trade 911s with him straight up as my brakes never squeal. He declined dang it.

[Gus Berges]

Yeah, PCCBs are known to squeal like a pig at a slaughterhouse.... The more I research about them (PCCBs, not pigs), the narrower the potential target market becomes (at least to me). Yes, there are quite a bit of advantages to them, but there are almost as many disadvantages to them, so in the grand scheme of things, not 100% sure what the big deal is all about.

Oddly enough, every time someone starts talking about converting ceramics to steel, a bunch of people jump on the subject like vultures saying they want the PCCBs. I think there are more people converting from PCCBs to steels than the other way around.

[aschen]

On the fence about carbon ceramics on a sports car, no thanks for me on a cayenne. To each his own but would be a deal breaker for me.

Heat tolerance above good cast iron brakes and massive weight savings are things that don't seem worth the effort on an SUV.


For some reason I was getting advertisements for an aftermarket PCCB rotor supplier a few months ago, seems like a good thing others can make these now. Don't know anything about pricing or quality however.


Also porsche has those funky carbide surfaced rotors as an in between these days, they are pretty expensive too

[911boost]

My experience is on a sports car, my GT3RS. I knew my brakes had track time and took that into consideration when making the purchase back in '18. I love them on my car, no brake dust, they do not make much noise at all, and massive weight savings which I cannot even feel on the street lol.

It seems to me you are worried about them, and that worry will always be there so I would pass and find one with steel brakes.

They are a huge plus when trying to sell a GT3, as I have never had a Cayenne I have no clue if they are in that world.

[Gus Berges]

Still waiting for the results of the PPI it had performed on Monday. Not sure what the delay is in getting me this information. If the measurements of the discs come back where there is little to no wear, then I'd consider getting the truck as I will essentially add ±30K miles and then sell it. If there is a chance that I'd be stuck with a $30K bill for brakes in that time (or right before selling), then I'll have to pass on this truck (a shame as it's otherwise perfect). Only other truck that I have seen in similar condition is a 2014 GTS, but because it has less than half the miles of this one and it's 3 years newer, the seller wants an additional $15K over this one (and goes back and forth whether he really wants to sell or not).

[911boost]

There are a lot of options cheaper than the Porsche PCCB’s if you need to replace them…. I got my spare set of Porsche CCB’s for all 4 corners less than just the front pair costs new.

[Gus Berges]

by all means, please enlighten me on what my options are when it comes to replace the PCCBs on a Cayenne Turbo! I know of ReDisc and that will be a ±$8500 solution and have the truck on jack stands for 45-60 days.

I need to research A LOT into what it would take to replace the ceramic pads/rotors for steel-based rotors & pads. No clue what it will cost to convert, or even if it's possible to do so, from PCCB (410mm fronts) on a Cayenne Turbo to steel. GiroDisc makes steel rotors this size, but apparently for the 997 market, unsure if for the 958 Cayenne. Not sure what else is required, nor the corresponding costs involved. If anyone knows of a definitive response to this, please let me know.

Front pair of PCCBs is still a ±$14K bill (assuming they could even split the order between fronts and rear as all I've found is the entire set with all 4 corners). In USA I can get them for $18K vs. the local $28K price, but then I'd void the CPO warranty on it.

[911boost]

I saw you found some of the threads on Rennlist Gus, there’s some good info there.

[Gus Berges]

Yeah, I posted over there too, but still have yet to find a definitive answer to changing from PCCB to steel on a Cayenne Turbo.

Posted over here my "summary" too as I thought it would be of interest to some and it took quite a bit of time and effort to condense that information to what seems to be simple enough.