Carbon Brakes - walk away or worth it?

[Steve Rance]

Porsche911R said:

And I bet 2 up with a 15 stone passenger and a trick brake set up you cannot lock the wheels at 140mph :-)

If stopping from 140mph on a dead straight at what speed do you think you need to threshold brake to stop a lock up or ABS cutting in ?

PS can I have a drive :-)

I think you are one of the best posters on PH the info is always real and backed up , it's very refreshing.

The 997 gen 1 cup that we does not have abs only an adjustable brake bias. Its interesting form the perspective of this thread because a locked wheel indicates the point where braking force is overcoming the pysical grip of the tyre.

Basically it is very easy to lock a wheel at any speed. To be quick in a 911 without abs you need your brake bias as far forward as you can get it (in the dry) so generally it's the fronts that will lock first. When the brakes are warm, and your bias is set correctly if you grab the brakes it is realtively easy to lock a front. which one will depend on the attitude of the car and the loads acting upon it during the application. if the driver is very clumbsy, its relativey easy to lock both fronts. If the bias is too far rearward, you will lock a rear - or both. Either way, without ABS its very easy to lock up at 140mph in a cup car at initial application, which by inference means that on a car with abs, it would be triggering a lot more that you would think. That would be different if the car was generating huge levels of downforce, perhaps with the benefit of ground effect but i've yet to drive a propper GT racing car that generated that level of down force.

[Neverbeen-too-fast]

user "Darude" from M5post.com

said this:

"
Sorry, the dealer didn't take any pictures of the rear rotors, I will post some once I've taken delivery this weekend. The front disc is 1 cm larger than the steel discs, the rears are the same, or so BMW have told me, I also spoke with an M specialist at the Geneva motor show 2 weeks ago where they had the CCB on the new M6 gran coupe and he also confirmed they were 1cm larger on the front. Interestingly, he said that the actual braking performance wasn't significantly better with the CCB, but resisted fade much better for aggressive driving, with no brake dust. He mentioned the unsprung weight had a big difference on the driving characteristics and pointed out that the actual discs have been designed to last the lifetime of the car! They have been running an M5 in house continuously, which has over 400,000km with the same discs. This should help recoup some of the £7600..."

[Kawasicki]

Neverbeen-too-fast said:

user "Darude" from M5post.com

said this:

"
Sorry, the dealer didn't take any pictures of the rear rotors, I will post some once I've taken delivery this weekend. The front disc is 1 cm larger than the steel discs, the rears are the same, or so BMW have told me, I also spoke with an M specialist at the Geneva motor show 2 weeks ago where they had the CCB on the new M6 gran coupe and he also confirmed they were 1cm larger on the front. Interestingly, he said that the actual braking performance wasn't significantly better with the CCB, but resisted fade much better for aggressive driving, with no brake dust. He mentioned the unsprung weight had a big difference on the driving characteristics and pointed out that the actual discs have been designed to last the lifetime of the car! They have been running an M5 in house continuously, which has over 400,000km with the same discs. This should help recoup some of the £7600..."

I worked on CCB brake development, carrying out ESP and ABS calibration. In 2 years using one car I wore though maybe 50 to 100 sets of brake pads, but I never needed to change the original discs. They were given a VERY hard time too, fitted to a powerful/heavy car and basically the only car that was taken was when fitting wheels.

I have no reason to doubt the experiences of others regarding wear, just that the discs I used were incredibly hard wearing/reliable.

[Dr S]

Slippydiff said:

Dr S said:

Just focus on what I wrote instead of making things up. Engineers tend to design braking systems fit for purpose. Please tell me in which world does a track exist where you could experience the type of braking scenario (including lack of cooling) that you suggest. I have not found one in my world but judging from the aggressiveness of your posts you must be certain to have found it in yours...

You' appear to have completely missed the point of the "brake dyno scenario" I suggested, hence the "where's the whoosh parrot" question. Early PCCB's wore out prematurely, not because the owners of the cars "didn't do a couple of cooling down laps after a track session", but because they overheated them whilst driving the cars, this in turn caused oxidization of the discs faces, which then wore out prematurely due to mechanical wear, this was then rapidly followed by de-lamination.

As for the "aggressiveness" of my posts ? Well I found out the hard way that the early PCCB's weren't up to the job. So despite doing my due diligence and having my prospective purchase inspected by Reading (who told me the PCCB's on the car were serviceable). They looked like this after the 170 mile drive home from picking the car up :



Sorting the issues cost me a lot of time and heartache :

https://www.pistonheads.com/gassing/topic.asp?h=0&...

But in sorting the GT2 brakes and chassis out, I garnered a huge amount of information about PCCB,s and carbon ceramic discs, along with the manufacturing process/s, but also the workings of the GT2/3 chassis In doing so I also "discovered" Surface Transforms and Center Gravity.

[Polite mode on] So when I read comments such as yours about PCCB's NOT being made of chocolate and requiring a couple of cool down laps to ensure they're longevity, I get a nasty nervous tick that brings out my "aggressive" side......[Polite mode off]

Modern PCCB's are now much better engineered to enable improved heat management, firstly by their size/mass, but also by their internal venting and cold air ducting on the chassis itself. Could you overheat them by abusing them ? probably, but why would you ? They've been engineered to do the job and no doubt have a decent safety factor built into their design, something that couldn't be said of the early iterations.

That explains a lot and I fully understand your frustration. The "quality" - or not - of the first iterations of PCCBs was a joke and Porsche definiveily lost a lot of credibility in the process.

I only started buying them from the 7.2 onwards. If I were doing proper track work with my road cars I'd surely stick with steels and a pad upgrade to contain cost.