Determining Carbon Ceramic Brake Disc Wear

[911boost]

If you want pictures of the like news one I can take one out of the crate and snap a few.

[masraum]

Originally Posted by Gus Berges

More info for future reference sake:

GiroDisc does not offer an option to replace the discs if the truck has the 1LX and 2EH options (410mm fronts and I believe 370mm rears) PCCB brakes.

Brembo too does not offer a direct replacement for the ceramic discs with the aforementioned options, but TPC Racing will in fact configure a kit consisting of hub adapters, Brembo GT calipers, discs, and pads for a total investment of ±$10.5K (plus shipping and labor).

Again, my hope is that this information proves to be useful in the future for someone considering the purchase of a CTT with PCCBs on it.

If you could sell the left over PCCB brakes to someone else to offset the cost of the TPC brakes, great other than the swap being a PITA. Otherwise, PCCBs on a Cayenne seem like a horrible idea unless you've got ridiculous amounts of disposable cash.

[masraum]

Originally Posted by Gus Berges

IOne thing is replacing PCCBs on a 958.1 Cayenne, another entirely different matter is replacing them on a Carrera GT.

Exactly. And if you can afford a CGT, I would think/hope you can or should be able to afford the maintenance on one.

I can also see someone looking at a vehicle and either 1 not thinking about the brakes or 2 thinking "cool, I'll have those cool PCCB," without considering the possible downsides.

I find it interesting that the correct method to determine the wear is by weight rather than the old fashioned method of measuring the thickness between the two brake surfaces.

Do these brakes lose mass without getting thinner? I'd love to have a better understanding of weight vs thickness as a measure of wear on these rotors.

My guess is that a lot of folks that say that the rotors are lifetime or last forever may be doing a "visual inspection". "Hey, those look a lot better than iron rotors usually look, so they must be fine." But if the correct method is to weigh them, then how they look is invalid. I suppose if there are also visual wear indicators, they may be looking at those, but a lot of folks think they know what's going on and talk like they do when they don't.

Fortunately, you've put in a lot of time researching and learning, and sharing your knowledge with us. Thank you

[Gus Berges]

Yeah, that board is not what it used to be, but the same can be said of many other boards (at least automotive ones). Maybe it's the new generation coming in and though I'll be 51 in a couple of weeks, I don't see myself as one of those "get off my lawn" type of people. Just for posterity sake, I'm adding this last bit of info here for future reference:


Just got back from the dealership where they gave me the figures for the % of wear (solely based on disc thickness) on each disc. They are as follows: FL: 23%, FR: 34%, RL: 15%, RR: 15%. Due to the difference between FL and FR (an extra 50%..) they decided to purchase a new measuring device as they could not believe the difference, but the new measuring device yielded the same results as their old unit. The initial maximum thickness was obtained by measuring the outside border of the disc as they claim there is a very slight "lip" on them. For each disc, they took the measurements at the wear indicators (3 per disc). Tech found it very odd that the rears have been used much less than the fronts as their experience (with iron rotors) is that the rears wear out much faster than the fronts. His concern also stems from the fact that there is more tire wear on the rears than the fronts and there is some issue with the PTV+ (implying it's been driven well). They have no explanation for the difference in wear between the two front discs. They did admit that it was a big learning lesson for them figuring all of this out and having to dig through tech manuals and documentation I provided them with.

Their measurements contradict what ReDisc states (solely based on picture sent of wear indicators). ReDisc claims that they are "at least" 50% worn and should be weighed to determine actual wear. Oddly enough, the pics I sent ReDisc are of the rear discs which show the least amount of wear as per the local dealer who claimed that he had to remove one of the rear discs as he could not find the wear indicator on the outside braking surface of the disc even with a loupe, but I could see it clearly, hence me having some doubts regarding the validity of their measurements....

[masraum]

Originally Posted by Gus Berges

Just got back from the dealership where they gave me the figures for the % of wear (solely based on disc thickness) on each disc. They are as follows: FL: 23%, FR: 34%, RL: 15%, RR: 15%. Due to the difference between FL and FR (an extra 50%..) they decided to purchase a new measuring device as they could not believe the difference, but the new measuring device yielded the same results as their old unit. The initial maximum thickness was obtained by measuring the outside border of the disc as they claim there is a very slight "lip" on them. For each disc, they took the measurements at the wear indicators (3 per disc). Tech found it very odd that the rears have been used much less than the fronts as their experience (with iron rotors) is that the rears wear out much faster than the fronts. His concern also stems from the fact that there is more tire wear on the rears than the fronts and there is some issue with the PTV+ (implying it's been driven well). They have no explanation for the difference in wear between the two front discs. They did admit that it was a big learning lesson for them figuring all of this out and having to dig through tech manuals and documentation I provided them with.

Their measurements contradict what ReDisc states (solely based on picture sent of wear indicators). ReDisc claims that they are "at least" 50% worn and should be weighed to determine actual wear. Oddly enough, the pics I sent ReDisc are of the rear discs which show the least amount of wear as per the local dealer who claimed that he had to remove one of the rear discs as he could not find the wear indicator on the outside braking surface of the disc even with a loupe, but I could see it clearly, hence me having some doubts regarding the validity of their measurements....

Very interesting.

Where in the photo that you posted in the visual wear indicator?

Not a great sign that the dealership seemed (and still does) pretty clueless. Granted, I'm sure they don't run into these on a daily basis, but you'd think they'd have at least one guy on staff that was really knowledgeable. But then that would probably eat into their profits too much.

[Gus Berges]

Hola Steve,

Post #1 on this thread gives you a summary on how to properly measure wear on ceramic discs, not just Porsche branded. The pre-2014 discs (or any other that don't have the Proceq markings) are the ones that require a visual inspection, followed by a thickness inspection, then followed by weight inspection. The truck I was looking has the older type of discs, hence unable to use the Proceq tool to accurately measure wear on the discs. Ceramics do lose weight (hence minimum weight stamped on the hub) as well as thickness (also stamped on the hub). Some claim that the thinner they get, the faster they lose mass. You are correct in the fact that there are a lot of people with incorrect information. I've taken the time to deeply investigate on the matter and share with the rest in order to help them a potential financial disaster.

If you take a look at post #52 you will be able to see the wear indicator on the disc near the outside border in front of the second "dimple" of the heat shield. Once you know what you are looking for, it will be clearly visible. The dealership has been somewhat open in admitting they are not subject matter experts, but based on all of the information I've read (factory tech manuals), I am going to trust my own observations and that of people whose business solely depends on dealing with ceramic discs.

I'm enclosing a 100% crop of the same image on post #52 so anyone can see what a wear indicator looks like up close (picture taken by me with my iPhone without zooming a few feet away from the vehicle).

[911boost]

So based on their measurements they claim there is lots of life left on the rotors. Is this a right hand drive Cayenne? Could that explain the wear on the right side front? More weight over there? I guess I have never determined if the drivers side wears more on anything as I always replace both fronts or rears (with iron) on normal cars at the same time.

The rear tires being worn more would be normal I would think. The rear gets a greeter % of the power, correct?

[Gus Berges]

This is a left hand drive Cayenne (just like in USA). No clue as to why it has wore off more on one side than the other at the front, but not at the rear. When I've replaced discs, I always have done both sides of the axle at once and in more than a couple of times, I've replaced all 4 corners even if a pair did not need it right away.

More rear tire wear is normal as these are heavily rear traction biased (62% rear, 38% front is what has been stated many times), so no issues there, but by the same design, the rear brake pads also (normally) wear out quicker as it's what Cayennes use to control tire spin/partial traction control. In this specific case, the rear discs show almost half as much wear as the fronts, something that they also don't have an explanation for (thus me having doubts about their measurements overall...).

There is a local owner that has a 958 Cayenne Turbo with iron rotors and he goes through rear pads every four months or so and new rear discs once a year. He also goes through rear tires twice as fast as the fronts. You'd think he drives a 930 instead!

[911boost]

Maybe the rears have already been replaced?

[Gus Berges]

Originally Posted by 911boost

Maybe the rears have already been replaced?

100000000000% sure this is not the case. All discs are original from new. This confirmed by the service record and furthermore by the date stamps on all of the discs (very similar to one another).

[911boost]

I would expect more wear on the fronts, but you were saying guys were replacing the backs due to the traction control etc....

What kills PCCB's is heat, hence track days being hard on them with repeated hard use. I wonder if the traction control etc is so infrequent it never heats them up, hence the less wear.

[masraum]

Originally Posted by 911boost

I would expect more wear on the fronts, but you were saying guys were replacing the backs due to the traction control etc....

What kills PCCB's is heat, hence track days being hard on them with repeated hard use. I wonder if the traction control etc is so infrequent it never heats them up, hence the less wear.

That was my thought, super relaxed driving by the lady that drives the car means no torque vectoring or traction control to increase rear brake wear. And possibly if all of the driving is super relaxed, that would also cause the fronts/rear bias difference in this vehicle.

[Gus Berges]

Never saw it that way and it is in fact a logical conclusion, to which I'd respond that the other owners definitely are not known to be "Driving Ms. Daisy" types...

I'm really torn as I really want this truck (due to purchase price, configuration and overall condition), but the PCCB potential issue really scares me off. If it were a $3K gamble, I'd take it, but a $30K gamble, well, it opens up a series of questions that makes me wonder...

[911boost]

Those have tons of life left, I say do it!!!

[Gus Berges]

One last bit of info to add. Here is an excerpt from the 2013 Porsche Cayenne brochure where it confirms there are in fact two PCCB sizes for Cayennes, but apparently the larger size is exclusive to the Turbo and GTS models. Maybe it could help someone in the future:

[Gus Berges]

Just for closure purposes, I passed on this Cayenne Turbo merely because of the uncertainty of the disc wear. As stated before, if it were a "gamble" regarding replacement cost equivalent to iron discs, or slightly more, I would have definitely purchased this vehicle, but due to the fact that the "gamble" entails a potential $30K bill (more than the purchase price of the vehicle), I've decided to look elsewhere and now potentially closing a deal on a 2013 Cayenne GTS with ±46K miles on it and iron rotors.

Hopefully the information I've provided will help others in the future.

[KNOKKi]

Newby here! From Amsterdam, The Netherlands. Hello everybody and thanks for having me.

This is a somewhat older thread, which gives a lot of info. However, there is one thing that I would like to solve and that concerns step 3 of the steps bu Gus: weighing the discs. Has anybody ever done that? I wasn't able to find anybody on the net who shared his or her experiences on that. The point is as follows:

My rear CCM discs may loose 70 grams each and the fronts 300 gram. This is clearly indicated on the discs which all have an individual weight to start with (also indicated). For instance, my fronts where 6634g and 6774g new and should be replaced at 6334g and 6474g the latest, respectively. Now I took off the disks after 95k kms and all the discs measured actually heavier than new. From a few grams to 20 grams (calibrated scale). We took the disc with the biggest increase and started to clean it intensively (there was some brake dust in the holes drilled into the surface for instance). After drying etc. this had no significant effect on the weight.

So that leaves the question what the relevance is of the minimum weight indicated on the CCM discs. Or the other way around, how do I weigh the discs ‘correctly’ cq what have I done wrong? The only thing I can think of is that the inner steel part of the discs will corrode to some extent during the years, and FeO is heavier than Fe. But then, this happens to all discs on every car and brings me again to the relevance of indicating a maximum weight loss. Who?

Best, Wieger

PS I am an avid anticipater, read non-braker. My fronts for instance are still 37,6mm (38mm when new). So my brakes are fine. Just trying to explain the relavance of the indicated weights.

[Gus Berges]

Hello Wieger and thanks for sharing your findings, odd as they may be. You measure that you have in fact worn the discs (37.6mm vs 38mm when new), yet you also mention "heavier than new" when weighed. Not sure if there is an error or not in either measurement (thickness or weight), but they seem to contradict each other. Perhaps use another scale or micrometer?

Weighing the discs is somewhat subjective in the sense that many variables come into play, among them, residual matter (dust) which could affect the final outcome, but it appears as if you have taken care to make sure this is not the case. You mention "after drying", so perhaps the discs were not as dry as you thought and they did in fact absorb water, thus the high weight reading? Just throwing out ideas.

[KNOKKi]

Hi Gus, thx for your reply. At least you read what I write. At Ferrari Chat they came up with all kinds of reactions which did not address my question, like 'measure thickness', 'buy a Carboteq', etc.

I don't understand why you use the word 'worn' in 'worn the discs', but that is maybe my English. The minimum thickness of the front discs is 36,3mm (38mm when new), so they may loose 1,7mm thickness. They are 37,6mm thick now, i.e., lost 0,4mm, so they are (0.4 / 1.7 =) 24% 'worn'. Can we agree on that? .

As with the weight, the fronts may loose 300 grams. Let's take one of the fronts which has an indicated weight when new of 6774 grams and (thus) a minimum weight of 6474 grams (also indicated on the disc). It actually weighs 6777 gram, while you would expect a loss of 0,24 x 300 grams = 70 grams and thus a weight of about 6700 grams. This is measured before any cleaning or so, but even then - looking at the disc - it is hard to see where to find 7 grams of dust, let alone the needed 70 grams.

As said, I have cleaned one of the discs (a rear disc) but that did not make any change, though quite honestly the rear discs may loose only 70 grams. The rears have lost 0,2mm width of a max of 0,5mm (32mm new, 31,5mm minimum), so they are (0,2 / 0,5 =) 40% worn - judged by their thickness - and thus should have lost around 28 grams, but as said they 'gained' weight. And again, I am willing to accept a few grams of hidden residual matter, but not the 50 grams that are needed here (i.e., the 28 grams wear and about 20 grams additional mass measured compared to new). There are no errors in measurements, everything done several times with calibrated scales and 2 persons present

So, the bottom line is 1) that I have 4 CCM discs which are between 20 and 40% worn and which all weigh more than when new and 2) that I haven't been able to find anyone else on the net who has been weighing used CCM discs (as opposed to measuring the thickness of used CCM discs), so I don't know whether my measurements are extraordinary. To be continued?