tlaritz

Nice catch ajw45. Below is the text of the note to my guy at the Porsche dealer. In my note below, I am alluding to the dealer's previous note which had the PCCB measurements attached."Hi again. I am trying to make some sense of the PCCB measurements, comparing with values from others. Do you know if the PCCB measurements were taken with the rotors removed from my car?"

His response is below:

Hi Tom,
Porsche has a special tool that measures the density of the ceramic discs in three different spots on each rotor without having to remove them. Some manufactures want to have weight measurements recorded which would require removal of the discs, Porsche also has a minimum weight requirement in case an independent shop without the special tool is servicing the car. Below are a couple pictures of a ceramic disc on a car here in our showroom. You’ll notice the #1 and #2 markings with density indicators (new / minimum) and there is a minimum weight marking as well. These pictures are from a 2018 GT2 RS which might be a little different than the GT4. In the past there wasn’t a tool or even a weight measurement available so determining wear on a ceramic disc had to be visually determined. Thanks to newer technology there’s no more guessing. If you have questions please don’t hesitate to ask, we’re here to help.

Thank you,

I have not included in this post the pics contained in his email response.

His response implies that the baseline procedure is making the measurements with the rotors on the car.
ajw45: What led you to believe that making the measurements on the car will lead to erroneous results?

ajw45

Experience

https://rennlist.com/forums/gt4/1032...r-and-ptv.html

tlaritz

ajw45: I read your thread and thanks for verifying that the readings vary significantly with rotors on vs rotors off.

What I am about to say will **** you off, but I will say it anyway. With all due respect, you got 2 answers and you assumed the answer with less wear was correct. Why?

Given all of the voodoo behind the measurement process, I see a switch to well-understood iron rotors in my future. I believe that the wear of cast iron rotors can be measured with a caliper, which is something I understand. I want to be absolutely sure on the track that my brakes are going to function correctly.

Please feel free to yell.

ajw45

One of the options below is true, you can choose to believe what you like.

A.I assumed the second one is correct because I paid over $300 to have it done (the first check was free) so I assume the tech did a better job.

B. I watched the same tech take each rotor off the car, place each on the same work table, measure each with the same tool, on the same day, in a climate controlled service center.

C. I have video of B.

D. None of the above, trolls be trolling.

E. B & C

johnsopa

Measurements on the car are not repeatable nor reliable. Measurements off the car are. BTDT.

tlaritz

I promise this will be my last response. I'll let others have the last word.

ajw45: You claim that on-car measurements are erratic, yet, as far as I can tell, you are assuming the on car measurements for the front rotors are correct. Isn't this cherry picking your results? Might checking the rotor wear of the fronts with those rotors removed help better explain your situation?

ajw45

Fronts measured about the same off the car so I didn't repost numbers.

I claim you might be crazy because I assume you are legitimately asking for help and being rude about it at the same time. I am cherry picking based purely on your posts in this thread, I haven't researched to see if you are trolling or a real person in desperate need of manners. Might simply asking whether the front rotors were also checked off the car instead of making claims about assumptions you assume I made better present your query without revealing an oddly presumptive and condescending tone?

Where's that block button, I know it's around here somewhere.....

IPSA

I did this drill 3 years ago w Porsche.

Step 1 , measure on the car. If not a good result , step 2, take the rotors off and put them on a wooden bench or something non metallic and measure again. This is the most precise measurement. Mine were bad on the car and mediocre off the car. The metal behind the rotor while mounted can cause less than accurate readings.

This is Porsche's internal method. 3 years ago not many dealers knew the drill. All should be up to date by now.

Rears on Gt4's tend to wear quicker because of traction control and PTV. PTV can not be turned off.

Larry Cable

looks like you turned right about 2x the # of times you turned left!

modernyankee

johnsopa, could you make that PCCB wear chart available? I have a 2021 Spyder w/ PCCB's and would like to supply data so we can get facts out there about how these things wear. I did 13 track days last year and expect to double that this year. I keep a detailed log of tracks, mileage, tire temps, ambient and track temps, etc... for every track day. I also had the foresight to get my PCCB's measured with the Carboteque measuring tool when the car was new (to verify factory specs). 1 year and 8000 miles (roughly 1500 of which were track miles...I'll dig through paperwork to get exact track miles) after taking delivery, I'm about to bring my car back for a re-measure of the carbon content. Like many others, I need to know the REAL cost of tracking PCCB's. Send me that spreadsheet and I'll gladly post my info. I have RSS links and as much neg camber as factory set up will allow...-2.4 deg front (that's also changing this month). I drive in the northeast. Watkins Glen is without a doubt the hardest on my brakes (vs Lime Rock, Palmer, Tamworth, NYST, Thompson)...and I don't know many who use the brakes as hard as I do. You and I sound like we'd be good bookends...you having momentum car experience (light on brakes) and me going for everything the car can give me (yes, heavy on brakes...and I could stand to modify my technique to be easier on the equipment and probably faster...I run 2:08 at WGI). Let's do this. Too few facts out there on this subject.

modernyankee

I'm not sure if this post will shed light on the PCCB wear/measurement issue but it'll sure spark some discussion. With the help of a willing Porsche Factory-Trained tech, his personal Carboteq measuring tool, a second (Porsche-owned) Carboteq tool and my money, we've recorded a pile of PCCB measurements. We have concluded that, in fact, the PCCB readings will be significantly lower (i.e. indicating MORE rotor wear) if the rotors are measured while still on the car (even with the rotors continually turned so that the measurement is taken as far away as possible from any metal). Additionally, you'll see in the chart below that we've recorded not only 'on vs off' measurements, but also the difference between two calibrated tools.
The only conclusions I can come to are these:
1) The rotors need to be measured while off the car and on a non-metal bench. My tech took all 'off the car' measurements with the rotor on a wood benchtop. Just look at the initial readings on the rear rotors (taken while on the car) when the car had only 2,175 street miles. The readings indicate the rotors are half way through their usable life! Measurements taken with the same tool by the same person on the same rotors (also measured while on the car) one year later (with nearly 1400 track miles and 6,000 more total miles) show that somehow I turned back time and ADDED carbon to my rotors while using them (LOL). Clearly, the conclusion is that measuring rotors while on the car results in readings which are grossly inaccurate.
2) To minimize inconsistency in the readings from one measurement session to another (to better gauge wear over time/usage), use the same technician using the same tool and the same procedures. Measuring with different tools (both calibrated), can result in different readings. And it's not as simple as one tool just reads consistently lower than the other...some of the measurements taken with Porsche's tool were higher than with the tech's tool and some were lower. No pattern.
3) PCCB's are expensive to run on the track. This is a whole other spreadsheet, but my PCCB wear rate indicates I would get roughly 8,000 track miles out of my front rotors and roughly 13,000 track miles out of my rear rotors. With a $27,000 PCCB rotor replacement cost (all 4 corners) and a set of stock pads every 1,400 track miles (I burned through pads at all 4 corners in under 1,400 track miles...9 track days), my PCCB's are costing me $470 per track day (assumes avg of 140 mi/day at track...fewer miles at smaller/slower tracks, more at bigger/faster tracks). A friend/instructor/GT4 driver and I were comparing actual life measured out of his Girodisk/Ferodo setup. We concluded that our cars were similar enough and while he probably wasn't as hard on brakes as I was, he also drove significantly more laps than I simply by being out there more often because of being an instructor. Using his wear rates, the Girodisk/Ferodo setup calculates to $59/day through a combination of lower cost components and significantly longer life for all of them. Less scientific, but I've also calculated costs based on manufacturer's predicted rotor life with Surface Transforms and Pagid pads, Rebrake with stock Porsche pads, Hinz discs w/ Ferodo pads. Based on MY usage (and making many assumptions on longevity of the products), ST & Rebrake should be roughly half the cost (of PCCB's w/ stock pads) per track day at $250/day. Hinz/Ferodo would be $80/day.
4) I'm tough on brakes and will work this year to adjust my driving stile to be easier on my my equipment...especially my brakes

I hope you find this data useful.

Buteo

Great post modernyankee!

Redisc

Hi guys, I am from the company Redisc from Slovenia, and we have bought the technology for refurbishment and repairs for CCB, www.redisc.si

As our references, we have already made 500 pcs (including for the company that is already well known in your forums for refurbishment, as we were his main supplier.. Now we have decided to start over, we have better and improved technology, new ownership and a very professional team.
We are also using Carboteq for extra quality.

If any one has any questions, you can contact us here on the forum.

artongdou

For who has asked dealer to measure PCCB? How much should I expect they charge for that? I am new Porsche owner so don’t yet have a good relationship with any dealer.

Redisc

Hi I have no idea, but this devide is very expensive.
What you can do is to put them off the car and weigh them. This will be a very good indication. Just check what is max and what is min. weight - is has to be written on the hat of the disc.