Ceramic Brakes (450)

Is this option really worth the 8K?

no

I have the standard brakes and it stops very well.

They are very much worth the money, and it's a mistake not to get them (IMO). The big differences in performance are 1) initial bite in the first half second, and 2) they are more durable under extreme heat conditions. The extra maintenance they demand requires you to cool them down carefully after tracking them. For track use use the P50 (green pad out of the GT3 Cup Car) but remember these have terrible performance when cold, and on the street use the P90.

How much do replacement rotors cost and how often do you need to replace them?

Colm, do you know where to get a set of the green pads for the GT2? I would like to try these with the cast iron rotors. Kerry, The Pccb rotors are around $4K each! P90 pads are around $300-350.

driver, If you plan on tracking your p-car alot, you should get them cause they are much better than the normal brakes. If you are like most of us, who mostly use the car on the car and may occasionally track the car, the normal brakes are more than adequate (hell they are some of the best brakes on the market), and the cost of maintaining the ceramics is PRICEY...

Oak, The pads can only be obtained from Porsche Motorsports North America (PMNA), I haven't had time to google for the number yet. I will be following up on this, and if I'm not successful there, I will identify a source in Germany, I'll be back there in 2 weeks.

Colm: I also have a GT3 with PCCB and have yet to take the car on the track. I am interested in your comment about special care in cooling the brakes after being on the track. What procedure do you follow? One or two cool down laps at the end of each track session? Is this cooling required even after you have switched to the green pads? In general, there does not seem to be much reliable information out there regarding PCCB on the new GT3. I guess that we will be the guinea pigs!!!

I don't want to represent myself as a track expert (I'm far from it), but here is what I do; use the cool down lap as a cool down lap, driving w/o using the brakes (or very lightly if must me) and concentrating on the "perfect" line (at least as perfect as I can make it, and it's easier at slower speeds) going all the way into the pits if possible without touching the brakes much, if they're really hot I'll take slow wide berths, meandering around the available area to let them cool even more. When I get to my parking spot, again I brake lightly and put the car in gear leaving the handbrake off.

Thanks Colm, Let me know if you find a easy and painless source.

This is hardly my experience. I agree with the "initial bite" comment (at least when the pads are new) but durability under heat is one of the biggest problems with the system. Query, are you speaking about the P50 pad from first-hand experience? I have none. But what I have heard is that cold performance isn't the issue, noise is. I've noticed little difference in cold performace between te P40 and P90 pad. Both work fine. I'll bet that the P50 on ceramics does too (though obviously follow factory recommendations to avoid liability issues). As for the cool-down lap ... ceramics are quite different to cast iron. They just don't absorb and conduct heat the way that cast iron does. That's one of the problems. Try touching it right after you have stopped. It isn't going to feel hot. With cast iron, the cool-down lap is to allow the stored heat ro dissapate out of the rotors so that it doesn't cook everything. What is the point of this with ceramics? Stephen

FixedWing, I have had no problems with the Ceramics, but I asked Roland Kussmaul, the Chief Engineer about the supposed problem (I was concerned about some posts here, and wanted to determine how big a problem it really was. The P90s are too soft for the track, but green pads are not good in the cold, he used an example where the stopping distance could be as great as 40 meters (two truck lengths) when the brakes are cold. I am inclined to give him the benefit of the doubt, and believe him over anyone else. After all he puts his life on the line everyday using ceramics at speeds that we can only dream about. You confuse me with your statement, you have heat related problems, but then you seem to advance the argument that it's not necessary to cool down the ceramics? Either they're hot or they are not. And if they're hot you have to get the heat out of them. In fact as I understand it the ceramics are capable of being heated to much higher temperatures than the steel without being subject to deformation. From my high school physics I seem to remember that there are only three ways of transferring heat:- conduction, convection and radiation. Therefore conduction doesn't begin to provide the whole story or explanation. I'm not a physicist and make no pretense about understanding all these matters. Maybe someone well versed in the laws of thermodynamics can weigh in with a knowledgeable opinion. The laws of physics haven't changed on earth (in a while), but maybe they behave a little differently on Jupiter! Is that the problem?

Colm, On the P50 pads, I too will defer to Mr. Kussmaul. The ceramic material conducts heat much more slowly than does cast iron. Cast iron will heat up relatively evenly. The ceramics will tend to heat unevenly. The surface of the ceramic material will become very hot but the heat is not conducted inwards to the rest of the rotor. On cast iron rotors, it is. This exacerbates the problem. The heating is localised and tends to be conducted more easily through the pads and callipers. Cast iron will absorb more heat and conduct it elsewhere. Since the ceramics don't absorb much heat, there isn't much heat to dissipate on a cool-down lap. On the cast iron rotors, they absorb a lot of heat so it is more important to dissipate that heat. The fact that ceramics don�t absorb much heat is the reason that you can touch them soon after use. Have you ever seen the demonstration where someone takes a blow torch and applies it to the Space Shuttle tiles? The tiles quickly glow red from the heat. But then they take the blow torch away and almost immediately it is possible to touch the tiles. Same idea. Jupiter is a cool place. Come visit sometime. Stephen

Aren't the pads and callipers hot, (or in your example even hotter). I think there is more to it. As an aside, I wonder if he meant the P40 (translation?) because I haven't seen any other references to the P50. But time will tell. I'll play safe and cool them down, nervous nellie that I am. It's a good habit to practice. By the way I can't find Jupiter on my navigation system.... Porsche gave me the wrong disc.

P50 is correct. It is the Pagid designation for them. The P40 is the softest pad. The Turbo with PCCB's comes with the P40 (and probably the C2 and C4S). Porsche will switch the GT2 to P40 pads if the customer complains about the noise. I first had P40 on my car and the last few sets have been P90. It is probably possible to see the P90 designation on the rear pads without pulling them. Probably it will say P90-II, the more recent version of the P90 pad. Jupiter is a big place but often missed. Alas, you will need to manually enter the coordinates. Stephen

Let me add my two cents. As a former engineer, this is how my calcified brain understands it: To make sense of what you guys are saying you have to distinquish between Heat and Temperature. Heat as used in this context is referring to energy not temperature. In addition to how conductive a material is (and related to it) is it's Heat Capacity. Metal has a high heat capacity, which means it takes a lot of energy to make it hot. Ceramics have a low heat capacity, so it takes relatively little energy to heat it up. That is why the space shuttle tile can be heated glowing red very quickly with a blow torch, but also cools off immediately. With a very low heat capacity it didn't absorb (and internally conduct) much energy, so there wasn't much energy to get rid of to cool down. Same with ceramic rotors - they cool down quickly because there wasn't much energy absorbed to begin with. The metal rotors on the other hand are excellent heat sinks and will absorb loads of energy and thus take a relatively long time to cool down. The puzzeling thing is this: the same weight car stopped in the same distance from the same speed, will have transferred the same amount of kinetic energy to the brakes whether metal or ceramic rotors are used. So where does that go with ceramic rotors? I'm guessing it partly goes more into the pads and calipers than with metal rotors. Hence the problem with the pads. I'm also guessing that the ceramic rotors just get much hotter than metal ones because to dissipate the same amount of energy from the stop, and with the lower heat capacity, they get must by definition get much hotter. (So what's the benefit of them being capable of working at higher temperatures then??? ) What this presumably means is the cool down isn't for the rotors, but for the pads and other components! Did I get it right? Did my remaining brain cells' pull it off? -Christian

Marx, Welcome. In my opinion, you got it exactly right. Yes, the heat is all going through the pads and the callipers. That's why these callipers have ceramic inserts in the pistons � to try to protect the fluid from boiling. And that is why it is essential to use Castrol SRF (or a good high temp DOT 4 fluid) if the brakes will see hard use. What's the solution? In my opinion, the brakes are good but need race car levels of air cooling similar to what is found on carbon/carbon systems. Because the system cannot easily absorb heat, it needs to be able to dissipate peak heat levels very quickly. Cast iron systems don't need this. They can even out their heat dissipation. The remaining question in my mind is how well these rotors conduct heat. I suspect not well at all. If I'm right, then the peak surface temperatures will be much higher than the average internal temperatures. And it also follows that the 30% greater internal airflow of the second generation rotors won�t make a lot of difference. Stephen

Christian, You have it correct. In fact, if you look a set of pads for the PCCB, they have a special backing plate in the pad to attempt to keep some of the heat emanating from the rotor from getting to the pistons, in addition to what Stephen noted in the calipers themselves. Porsche confirms what you have stated with the specification of the PCCB pads and calipers. To me the best indicator of the track worthiness of these pads is to see if any race teams are using them. Brakes are free in ALMS and Le Mans and I don't see any GT3 RS cars running PCCB. Instead they use very expensive floating hat steel rotors. The Super Cup, Grand Am Cup, and Carrera Cup cars all run the 6 pot calipers with steel rotors, same as the GT3 street car. If steel is good enough for them, it's good enough for me. Karl

I also agree. The coefficient of heat transfer of ceramic material is less than cast iron. So a ceramic rotor absorbs less kinetic energy of braking than a cast iron rotor does. Vents in a ceramic rotor are less effective because there is less heat inside the rotor to get rid of. The heat that isn't absorbed by a ceramic rotor goes into the other brake components or into the environment during braking, rather than being stored by a cast iron rotor to be released during the acceleration period after braking. So in one sense, a ceramic rotor of a certain physical size is equivalent to a cast iron rotor of smaller size. A smaller cast iron rotor has the same result under heating: it absorbs less and heats the other brake components more. So if you switch to a ceramic system but don't improve pad compounds and external cooling, you may be asking for trouble. You might as well switch to smaller cast iron rotors. Like ceramic, you will save weight. But unlike ceramic, you will save money. In a sense the weight savings of a ceramic system is not at much as you might think.