PCCB out braked the steels last night on 5th gear.

[JulierPass]

cayman-black said:

Funny all those saying they prefer steels, yet the GT cars without PCCB,s are cheaper and hang around longer, strange.

It is wierd. I specced my 991.1 RS with ceramics. I did a handful of UK days of circuit and 2 days at spa and 2 at the ring. I ended up speccing steels on my 991.2 GT3 and much prefer them. Unless ceramics on a car are standard and you can't spec steels, I would always go with steels. It's a bonus that they are cheaper as well.

[JulierPass]

MDL111 said:

isaldiri said:

MDL111 said:

My bad - but the cost argument might hold up then?
I’d obviously prefer steels for exactly that reason

Given the running costs of GT3 nevermind GTE, I rather doubt cost was the primary reason!

You might have a point there

If memory serves, I don't think there was any advantage to it, and (I think) wear rates were quite poor.

[ttdan]

If you’ve not got a bottomless pit of money then best rule of thumb is steels for track car and ceramics for a road car.

Ceramics are superfluous in both uses though. Excellent marketing by Porsche and you can bet the ROI on the options end of the sales results are pretty convincing to keep it going for a long while yet.

[FrankCayman]

£5K if you prefer yellow and don't like brake dust...that's it, really....

[ChrisW.]

isaldiri said:

But they have to given carbon ceramic has much less heat capacity per unit mass than iron... Porsche once upon a time had ceramics about the same size as the steels and that didn't end too well....

On a gt car where iirc the calipers are the same ie pad clamping force/area are equal, the difference in performance isn't going to be there. In any case even if tyre grip wasn't the limiting factor, one has a far greater choice of pads for iron brakes if one really wanted to try to add more braking capability.

Sorry Isaldiri, but you are confusing your science.
1. Carbon / ceramic discs have less thermal mass than steels, so they heat up faster and cool down faster for a given cooling capacity.
2. Carbon brakes can get much hotter than steel without fade and it's the greater temperature difference that massively accelerates the energy transfer out of the disc into the environment. I believe heat transfer is proportional to the fourth power of the temperature difference ... I'm sure somebody will confirm the actual value.
3. The PCCB's are fundamentally flawed because they are a laminate and the glue restricts heat soak from the surface layers which at a certain temperature, burns off.
4. Steel discs of the size of carbon would be a nightmare in terms of their gyroscopic and inertial effects on suspension and steering .. mass .. slow to heat and slow to cool .. cars would be coming into the pits with brake pad material in flames.
5. The Surface Transform discs that i have fitted are long fibre solid carbon which is a little heavier than the laminated discs but in terms of conductivity, behave a little like metal. So they wick heat away from the surface into the hub carrier and wheels but in the heavy braking heat up very quickly so that far more heat is ventilated.
6. A side by side test with a CR on steels at Oulton. I was lapping in '58's and the CR was lapping in 02's ... with two cooling down laps I came in with the front discs at 140C and the rears at 70C. The CR came in with the fronts at over 200C and the rears at I believe 225C. Kevin may be able to remember the numbers better.
7. With PCCB's my brake pads to half worn used to last three track days. With the AP's they last a full season of around 15 track days. The PCCB pads had the consistency of sugar loaf when removed, the ST pads looked ready to go another season. They are the same Pagid pads.

David is right on the button of the fifth gear findings so this is not a reason to berate him.

But I do recall his saying that the tyres limited maximum braking effort and so there was no advantage to carbon brakes.

Look now at the cost of replacement GT steel discs and pads.

ST's for a serious trackday driver are a no brainer ... mine are now half paid for in pad cost and I welcome any inspection of the disc condition. The PCCB's are boxed up, almost new ... only two sets of pads used !

Added to this, if you stick them in the kitty litter they can be skimmed .. better than steel, and hard as ... carbon.

Edited by ChrisW. on Friday 15th November 20:34

[ChrisW.]

FrankCayman said:

£5K if you prefer yellow and don't like brake dust...that's it, really....

You are right, if you can't feel the difference in the steering and agility of the car, you don't need them.

What percentage of press cars are supplied with PCCB"s ?

[ChrisW.]

ttdan said:

If you’ve not got a bottomless pit of money then best rule of thumb is steels for track car and ceramics for a road car.

Ceramics are superfluous in both uses though. Excellent marketing by Porsche and you can bet the ROI on the options end of the sales results are pretty convincing to keep it going for a long while yet.

Wrong. If you want to use the car as PGT's are intended, the ST discs are much cheaper over a four or five year cycle and you still have most of the value of the ST discs.
But .. with the latest GT cars you can now fit ST's to a steel disced car ... now that's thought !

[ttdan]

ChrisW. said:

ttdan said:

If you’ve not got a bottomless pit of money then best rule of thumb is steels for track car and ceramics for a road car.

Ceramics are superfluous in both uses though. Excellent marketing by Porsche and you can bet the ROI on the options end of the sales results are pretty convincing to keep it going for a long while yet.

Wrong. If you want to use the car as PGT's are intended, the ST discs are much cheaper over a four or five year cycle and you still have most of the value of the ST discs.
But .. with the latest GT cars you can now fit ST's to a steel disced car ... now that's thought !

Not sure what ST means and not sure what that makes what I said wrong?

[ab8]

ChrisW. said:

But .. with the latest GT cars you can now fit ST's to a steel disced car ... now that's thought !

How does that work - do they push the calliper out with a bracket to fit them?

Edit: I've looked, and yes that appears to be the answer. Not bad.

Edited by ab8 on Friday 15th November 21:18

[MDL111]

ChrisW. said:

ttdan said:

If you’ve not got a bottomless pit of money then best rule of thumb is steels for track car and ceramics for a road car.

Ceramics are superfluous in both uses though. Excellent marketing by Porsche and you can bet the ROI on the options end of the sales results are pretty convincing to keep it going for a long while yet.

Wrong. If you want to use the car as PGT's are intended, the ST discs are much cheaper over a four or five year cycle and you still have most of the value of the ST discs.
But .. with the latest GT cars you can now fit ST's to a steel disced car ... now that's thought !

Always follow your posts on the STs with interest as once my discs are toast, I will probably get those (and give up my warranty) - it sounds like you are very happy with them

[isaldiri]

ChrisW. said:

Sorry Isaldiri, but you are confusing your science.

I beg to differ

ChrisW. said:

1. Carbon / ceramic discs have less thermal mass than steels, so they heat up faster and cool down faster for a given cooling capacity.
2. Carbon brakes can get much hotter than steel without fade and it's the greater temperature difference that massively accelerates the energy transfer out of the disc into the environment. I believe heat transfer is proportional to the fourth power of the temperature difference ... I'm sure somebody will confirm the actual value.
3. The PCCB's are fundamentally flawed because they are a laminate and the glue restricts heat soak from the surface layers which at a certain temperature, burns off.
4. Steel discs of the size of carbon would be a nightmare in terms of their gyroscopic and inertial effects on suspension and steering .. mass .. slow to heat and slow to cool .. cars would be coming into the pits with brake pad material in flames.
5. The Surface Transform discs that i have fitted are long fibre solid carbon which is a little heavier than the laminated discs but in terms of conductivity, behave a little like metal. So they wick heat away from the surface into the hub carrier and wheels but in the heavy braking heat up very quickly so that far more heat is ventilated.
6. A side by side test with a CR on steels at Oulton. I was lapping in '58's and the CR was lapping in 02's ... with two cooling down laps I came in with the front discs at 140C and the rears at 70C. The CR came in with the fronts at over 200C and the rears at I believe 225C. Kevin may be able to remember the numbers better.
7. With PCCB's my brake pads to half worn used to last three track days. With the AP's they last a full season of around 15 track days. The PCCB pads had the consistency of sugar loaf when removed, the ST pads looked ready to go another season. They are the same Pagid pads.

1) Well we agree carbon ceramic has less thermal mass. Ultimately that means a 380mm steel rotor is going to be able to absorb a lot more heat than the carbon ceramic one whether 410mm or 390mm as it weighs a hell of a lot more. braking is basically shifting kinetic energy into heat in the end. Iron has more thermal capacity.
2) Well yes the ceramic rotors does get hotter and while you are transferring more radiant energy out due to the higher temperature, it'd be preferable to keep the temperature lower in the first place surely....
3) Carbon starts oxidizing above a certain temperature, it's not just an issue of the glue.
4) well the only times I've ever seen cars coming into the pits with brake pads on fire were on ceramic shod cars. As earlier, iron rotors can run them at lower temps.
6) the cayman r probably doesn't have the same braking cooling available as a gt4.

ChrisW. said:

David is right on the button of the fifth gear findings so this is not a reason to berate him.

But I do recall his saying that the tyres limited maximum braking effort and so there was no advantage to carbon brakes.

Re the latter, he used to say that when he had his gt4 on steels before he had the ceramic brake gt3. And now he is proclaiming this 5th gear 'test' as definitive proof of the superiority of ceramics while conveniently ignoring the earlier evo and motortrend (or car and driver I don't recall) doing similar tests showing that there was little to no difference in braking performance.

I'll repeat myself earlier - brake material choice is really not as big a deal as it's sometimes made out here. Especially with good non OEM choices available, both with Surface transforms as you mention but also Alcon/AP/Girodisc 2 piece steel rotors. People get overly evangelical about their choice as the only/best choice. I don't particularly have a strong opinion but if racing cars can cope in endurance racing with 380mm steel rotors and slick tyres, I think as far as braking performance is concerned, they are let's just say probably sufficient. If the other aspects of ceramics appeal (lighter weight, lack of dust etc) appeal enough then great but if not it's really not the end of the world.

Edited by isaldiri on Friday 15th November 22:20

[Slippydiff]

isaldiri said:

ChrisW. said:

Sorry Isaldiri, but you are confusing your science.

I beg to differ

ChrisW. said:

1. Carbon / ceramic discs have less thermal mass than steels, so they heat up faster and cool down faster for a given cooling capacity.
2. Carbon brakes can get much hotter than steel without fade and it's the greater temperature difference that massively accelerates the energy transfer out of the disc into the environment. I believe heat transfer is proportional to the fourth power of the temperature difference ... I'm sure somebody will confirm the actual value.
3. The PCCB's are fundamentally flawed because they are a laminate and the glue restricts heat soak from the surface layers which at a certain temperature, burns off.
4. Steel discs of the size of carbon would be a nightmare in terms of their gyroscopic and inertial effects on suspension and steering .. mass .. slow to heat and slow to cool .. cars would be coming into the pits with brake pad material in flames.
5. The Surface Transform discs that i have fitted are long fibre solid carbon which is a little heavier than the laminated discs but in terms of conductivity, behave a little like metal. So they wick heat away from the surface into the hub carrier and wheels but in the heavy braking heat up very quickly so that far more heat is ventilated.
6. A side by side test with a CR on steels at Oulton. I was lapping in '58's and the CR was lapping in 02's ... with two cooling down laps I came in with the front discs at 140C and the rears at 70C. The CR came in with the fronts at over 200C and the rears at I believe 225C. Kevin may be able to remember the numbers better.
7. With PCCB's my brake pads to half worn used to last three track days. With the AP's they last a full season of around 15 track days. The PCCB pads had the consistency of sugar loaf when removed, the ST pads looked ready to go another season. They are the same Pagid pads.

1) Well we agree carbon ceramic has less thermal mass. Ultimately that means a 380mm steel rotor is going to be able to absorb a lot more heat than the carbon ceramic one whether 410mm or 390mm as it weighs a hell of a lot more. braking is basically shifting kinetic energy into heat in the end. Iron has more thermal capacity.
2) Well yes the ceramic rotors does get hotter and while you are transferring more radiant energy out due to the higher temperature, it'd be preferable to keep the temperature lower in the first place surely....
3) Carbon starts oxidizing above a certain temperature, it's not just an issue of the glue.
4) well the only times I've ever seen cars coming into the pits with brake pads on fire were on ceramic shod cars. As earlier, iron rotors can run them at lower temps.
6) the cayman r probably doesn't have the same braking cooling available as a gt4.

ChrisW. said:

David is right on the button of the fifth gear findings so this is not a reason to berate him.

But I do recall his saying that the tyres limited maximum braking effort and so there was no advantage to carbon brakes.

Re the latter, he used to say that when he had his gt4 on steels before he had the ceramic brake gt3. And now he is proclaiming this 5th gear 'test' as definitive proof of the superiority of ceramics while conveniently ignoring the earlier evo and motortrend (or car and driver I don't recall) doing similar tests showing that there was little to no difference in braking performance.

I'll repeat myself earlier - brake material choice is really not as big a deal as it's sometimes made out here. Especially with good non OEM choices available, both with Surface transforms as you mention but also Alcon/AP/Girodisc 2 piece steel rotors. People get overly evangelical about their choice as the only/best choice. I don't particularly have a strong opinion but if racing cars can cope in endurance racing with 380mm steel rotors and slick tyres, I think as far as braking performance is concerned, they are let's just say probably sufficient. If the other aspects of ceramics appeal (lighter weight, lack of dust etc) appeal enough then great but if not it's really not the end of the world

Good posts from both of you
Agree, the PCCB issues centre on the wear faces themselves (rather than the bonding agent used to affix them to the substrate)
More specifically, the issue in the early iterations was due to a lack of mass in the disc itself along with poor internal and external cooling.

The wear faces are incredibly resistant to wear IF they’re running within the manufacturers temperature window.
Once that temperature window is exceeded, oxidisation becomes the issue, and then wear does indeed take place, and regrettably more often than not at a grossly accelerated rate.

Once the wear face is thin, it rapidly delaminates from the substrate beneath.

Whilst a 400/410mm steel disc along the lines of a PCCB disc would indeed be incredibly heavy Chris, the average disc this size will have a far narrower annulus, and as a result the bell will remove huge amounts of weight that would otherwise be present. These large diameter discs will have large numbers of internal vanes, firstly to provide mass, but more importantly to ensure adequate internal airflow for cooling purposes.

Edited by Slippydiff on Saturday 16th November 17:51

[ChrisW.]

The carbon discs heat up faster to a higher temperature but because they can cool so much faster (due to the larger temperature differential between the disc temperature and the ambient temperature), they dissipate the heat energy much faster.
Cooling down laps are still required ... so I accept that without this it is possible to come into the pits with cherry red discs that will cause trouble ... naturally solved on the cooling down lap.
Then add all the other advantages ...
Steel discs and pads from Porsche are now expensive ...
(Thanks Slippy )

Edited by ChrisW. on Saturday 16th November 17:48

[ChrisW.]

ttdan said:

Not sure what ST means and not sure what that makes what I said wrong?

Sorry ... ST stands for Surface Transform who manufacture a sold long fibre carbon disc which is expensive, but "cheaper" than Porsche replacements and I am very impressed with mine.

Aston Martin have used them for the Valkyrie ...

[Slippydiff]

ChrisW. said:

ttdan said:

Not sure what ST means and not sure what that makes what I said wrong?

Sorry ... ST stands for Surface Transform who manufacture a sold long fibre carbon disc which is expensive, but "cheaper" than Porsche replacements and I am very impressed with mine.

Aston Martin have used them for the Valkyrie ...

And the Konigsiegg (sic) ? many years prior to AML

You’re welcome BTW Chris I wish I’d kept my ST discs off the GT2, they would have worked perfectly on a Cayman R or similar ...

[isaldiri]

ChrisW. said:

The carbon discs heat up faster to a higher temperature but because they can cool so much faster (due to the larger temperature differential between the disc temperature and the ambient temperature), they dissipate the heat energy much faster.

But that's neither here nor there though. A brake rotor at higher temperature than another dissipating heat faster is expected due to the higher temps after all. That in itself is not a benefit (and I still think all things being equal one would prefer to have everything at a lower temperature if possible).

What will matter will be the capability of the braking system not to exceed the maximum advisable operating temperature (whatever that may be) given the amount of heat it is having to absorb due to the car slowing down over certain distance, say 10 laps or whatever number of laps one wants to do in a stint. in a current GT car (well maybe not a 2rs) - both ceramic and iron even OEM nevermind aftermarket are by and large able to do that in my experience.

[cayman-black]

isaldiri said:

that's mainly a UK thing only. in Germany where the gt cars are generally used on track a hell of a lot more, steel brakes are very much the norm there irrespective of the so called performance advantage claimed by some....

People can get overly hung up with their choice of brake material anyway imo. Both work and if you strongly prefer one good for you but there's no need to constantly trumpet it as the best thing ever (usually on their car which is also the best car ever....)

Yes I noticed this when looking in Germany that nearly all the RS,s were fitted with steels.
If you intend to track your GT car then i agree steels would be the better option, if used only for fast road driving then the PCCB,s would be a good choice.

As most on here seem to track there GT cars at some point i find it strange that the PCCB option is so sort after on the second-hand cars...

[MDL111]

cayman-black said:

isaldiri said:

that's mainly a UK thing only. in Germany where the gt cars are generally used on track a hell of a lot more, steel brakes are very much the norm there irrespective of the so called performance advantage claimed by some....

People can get overly hung up with their choice of brake material anyway imo. Both work and if you strongly prefer one good for you but there's no need to constantly trumpet it as the best thing ever (usually on their car which is also the best car ever....)

Yes I noticed this when looking in Germany that nearly all the RS,s were fitted with steels.
If you intend to track your GT car then i agree steels would be the better option, if used only for fast road driving then the PCCB,s would be a good choice.

As most on here seem to track there GT cars at some point i find it strange that the PCCB option is so sort after on the second-hand cars...

Must have item like a leather dash and deviated stitching
Just kidding (kinda..)

[Spyder75]

I asked Manthey about PCCB wear and they said they haven’t replaced a set of discs yet (since 2016) except a guy who ran the pads to the backing plates. Apex are expecting 30k ring kms on their gt2 rs.

They also use a different pad which helps disc wear. I don’t recall the exact conversation but I think the gist was the material doesn’t smear like OEM and as a result less heat builds up.

It was at this point I stopped worrying about PCCB wear and am enjoying them for what they are. Phenomenal stopping power and I’m sure a massive contributing factor on how the car drives especially on our terrible road surfaces.

[Dr S]

JulierPass said:

I haven't seen the article as I don't watch 5th gear. However, there is a reason why all of the factory built Porsche Cup Cars and R's have steel brakes. If the advantage was as pronounced as your post suggests then the race would come with ceramics from the factory.

There are plenty of race series where carbon brakes are not allowed