GT2 brakes (Ceramic) = useless
10-05-2003, 04:20 AM
#16
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Rocket,
Technically correct (though I'm not sure how much of an issue "green fade" is today -- I've not experienced) but I still don't think it is correct to call boiled fluid "fluid fade". What's fading??? The fluid is boiling, not fading.
But maybe others know better?
Stephen
Technically correct (though I'm not sure how much of an issue "green fade" is today -- I've not experienced) but I still don't think it is correct to call boiled fluid "fluid fade". What's fading??? The fluid is boiling, not fading.
But maybe others know better?
Stephen
10-05-2003, 04:09 PM
#17
gl911
I was advised that there are at least 4 comb of pads for the PCCB.
In fact, one's not even listed in the books.
My 03 came with the 'yellow 'pads and I have not experience any
concerns as yet.
Then, I don't run the S--it out of it like some do ... I have another Porsche for that.
I was advised that there are at least 4 comb of pads for the PCCB.
In fact, one's not even listed in the books.
My 03 came with the 'yellow 'pads and I have not experience any
concerns as yet.
Then, I don't run the S--it out of it like some do ... I have another Porsche for that.
10-05-2003, 05:48 PM
#18
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0396: There's 3 different sets of pads for PCCB brakes from Porsche. The "Street" and "Comfort" pads are standard dealer channel parts. The "Race" pads are only available from Porsche Motorsports (although some dealers have a clue enough to order them for you if you ask). That's more than 4 combinations if you mix and match but I don't think mixing and matching is a good idea in this case.
10-05-2003, 07:32 PM
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Watt:
Answer is yes, it should apply to a 2001 S class too, let us know. Should be the same for the US as it is here in Europe.
To all, I got the advice not to post the person's (engineer) email here. Nevertheless I have asked for a detailed write up of the encountered failures so far, including the ones that came up during "official" Porsche testing, to help those of you who might experience problems.
I also got a mail with a surprising attitude, and here is my answer:
This is not an anti-Porsche posting at all, as I love them and have had many of them including my new 996TT. I just started this post because I drove a GT2 and had the brakes (technically brake pedal) not responding after four laps, which I found quite amazing. And it was also prompted by talking to an engineer with whom we were trying to solve this issue, and he was the one who provided quite a bit of insight into the Porsche internal workings on this particular matter of PCCBs.
As stated before I will be glad to share my findings on this topic.
Answer is yes, it should apply to a 2001 S class too, let us know. Should be the same for the US as it is here in Europe.
To all, I got the advice not to post the person's (engineer) email here. Nevertheless I have asked for a detailed write up of the encountered failures so far, including the ones that came up during "official" Porsche testing, to help those of you who might experience problems.
I also got a mail with a surprising attitude, and here is my answer:
This is not an anti-Porsche posting at all, as I love them and have had many of them including my new 996TT. I just started this post because I drove a GT2 and had the brakes (technically brake pedal) not responding after four laps, which I found quite amazing. And it was also prompted by talking to an engineer with whom we were trying to solve this issue, and he was the one who provided quite a bit of insight into the Porsche internal workings on this particular matter of PCCBs.
As stated before I will be glad to share my findings on this topic.
10-05-2003, 08:09 PM
#20
Nordschleife Master
Originally posted by FixedWing
Rocket,
Technically correct (though I'm not sure how much of an issue "green fade" is today -- I've not experienced) but I still don't think it is correct to call boiled fluid "fluid fade". What's fading??? The fluid is boiling, not fading.
But maybe others know better?
Stephen
Rocket,
Technically correct (though I'm not sure how much of an issue "green fade" is today -- I've not experienced) but I still don't think it is correct to call boiled fluid "fluid fade". What's fading??? The fluid is boiling, not fading.
But maybe others know better?
Stephen
It might be a generalization including boiling fluid into the fade category, but won't you agree they have simliar results???
Pad fade, the friction coefficient decreases so that stopping ability is diminished.
Fluid boil, the bubbles that form compress under braking diminishing the pressure applied to the pads given the same foot pressure, hence diminished stopping ability. Just my common two cents...
10-06-2003, 10:03 AM
#21
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Two things about PCCB with the yellow "Sport Pads". First, it takes a long time to break them in. Using the usual technique (www.stoptech.com) didn't work. Green pads do not brake at all well and will boil the fluid, toast the pads and generally spoil your fun.
Secondly, the pad material fills the holes in the rotors. When that happens braking efficiency goes down by half. By breaking in the pads for 3 x as long as normal race pads and keeping the holes clean I have had no problems in the track with mine.
Secondly, the pad material fills the holes in the rotors. When that happens braking efficiency goes down by half. By breaking in the pads for 3 x as long as normal race pads and keeping the holes clean I have had no problems in the track with mine.
10-06-2003, 01:02 PM
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Something is out of whack here!
The GT2 comes standard with the yellow pads, and they're OK for DE.
For track use you want the green pads (PS50), they're no good when cold and best when warm, very hard and short braking required.
I got this info directly from the Chief Design engineer, and had it verified when at the Frankfurt auto show by other engineers.
Bedding the brakes...well that's a technique.
I leave open the possibility I misinterpreted something..but it'll take good evidence to convince me.
The GT2 comes standard with the yellow pads, and they're OK for DE.
For track use you want the green pads (PS50), they're no good when cold and best when warm, very hard and short braking required.
I got this info directly from the Chief Design engineer, and had it verified when at the Frankfurt auto show by other engineers.
Bedding the brakes...well that's a technique.
I leave open the possibility I misinterpreted something..but it'll take good evidence to convince me.
10-08-2003, 01:45 AM
#23
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AW,
You mentioned you saw a GT2 on race tires at Laguna? Was the owner Greg Scott, curlyish hair, mustache, parked next to a couple of Datsun and Nissan Zs?
If so, he was running hoosiers, and he is experienced and fast. Were you running green flag btw? I was going to attend that, but work came up and I decided to schedule for the Jim Russell 3 day Techniques of Racing school instead.....
You mentioned you saw a GT2 on race tires at Laguna? Was the owner Greg Scott, curlyish hair, mustache, parked next to a couple of Datsun and Nissan Zs?
If so, he was running hoosiers, and he is experienced and fast. Were you running green flag btw? I was going to attend that, but work came up and I decided to schedule for the Jim Russell 3 day Techniques of Racing school instead.....
10-08-2003, 02:23 AM
#24
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Originally posted by cjv
We ran a GT2 in the 1/4 mile at Infineon. We beat his trap speed by over 20 mph. We were able to brake and make the first turn out, he was not able to slow down fast enough to make the same exit. When he got back he was complaining about his ceramic brakes not being able to slow him down fast enough.
We ran a GT2 in the 1/4 mile at Infineon. We beat his trap speed by over 20 mph. We were able to brake and make the first turn out, he was not able to slow down fast enough to make the same exit. When he got back he was complaining about his ceramic brakes not being able to slow him down fast enough.
10-08-2003, 12:51 PM
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i think we are looking at different issues here - IMHO
1. Brake Fluid boiling
2. Driving styles
3. the disc/pad break in
4. heat retention /disapation in the rotor and hub
5. heat differencial in the rotor/pad interface - as they will cool off at different rates
6. heat transfer from Pad to caliper - which could be spot boiling the fluid
and a few other issues
F1 has been using the Carbon/carbon and Carbon/ceramic brake system for a while now and they are extreemly robust for the race - however they are replaced after every race.
I think porsche did a good job with this system it's just that this is not a Racing system - i.e. no teams are using a carbon/ceramic system in endurance racing that i know of (at least on porsche's). well not yet anyway.
I think that we would need to have to test they system to find out which one of these points is causing the issue. This is expensive however and for DE just not worth it.
In the mean time i would sugest the following to fix the problem.
1. additional ducting to the Hub & rotor- this will help carry heat away from the rotor and the disc
2. a break fluid recirculating system to help bring the fluid down in temp - there are several systems out there which can be addapted to work with the 996
3. Castrol 600 degree fluid
4. changing to an Racing brake system (keep you PCCB however)
all in all - i believe that this system will las the life of the car if used on the street and of course considerably less when used on the track.
All IMHO....
1. Brake Fluid boiling
2. Driving styles
3. the disc/pad break in
4. heat retention /disapation in the rotor and hub
5. heat differencial in the rotor/pad interface - as they will cool off at different rates
6. heat transfer from Pad to caliper - which could be spot boiling the fluid
and a few other issues
F1 has been using the Carbon/carbon and Carbon/ceramic brake system for a while now and they are extreemly robust for the race - however they are replaced after every race.
I think porsche did a good job with this system it's just that this is not a Racing system - i.e. no teams are using a carbon/ceramic system in endurance racing that i know of (at least on porsche's). well not yet anyway.
I think that we would need to have to test they system to find out which one of these points is causing the issue. This is expensive however and for DE just not worth it.
In the mean time i would sugest the following to fix the problem.
1. additional ducting to the Hub & rotor- this will help carry heat away from the rotor and the disc
2. a break fluid recirculating system to help bring the fluid down in temp - there are several systems out there which can be addapted to work with the 996
3. Castrol 600 degree fluid
4. changing to an Racing brake system (keep you PCCB however)
all in all - i believe that this system will las the life of the car if used on the street and of course considerably less when used on the track.
All IMHO....
10-09-2003, 11:03 PM
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Ok, so here are some comments that I translated:
The first and most important one is that ceramic brakes are mostly a marketing plot. Why charge a lot of money for brakes that add a lot of problems while the std Porsche brakes have been known to be the best in the business? To make more money - as simple as that.
According to the engineer these brakes ( ceramic ) will not work the way they should/could because:
Ceramic is an excellent isolator but it does an extremely poor job at absorbing and dissipating heat. The heat generated during heavy braking is not being taken by the ceramic disc. In addition to this, the ventilation is very poor, because it is currently technically impossible to make really sophisticated and "filigrane" vanes with a large surface to dissapate heat quickly from the ceramic disc. This is due to the extremely complicated maufacturing process for ceramic discs.
Thus the heat stays there and goes through the pads to the specially-isolated pistons and into to the fluid. Brake pedal failure is the consequence, which is what I experienced at Spa.
Next, the reason why the ceramic discs are bigger ( 350 mm ) than the stock turbo 996 discs ( 330 mm ) is again only due to temperature. The same holds true for the bigger caliper ( 6-piston ) and the much bigger
pads ( 115 cm² instead of 75.5 cm² ).
The very first pads used with the ceramic disc ( same as the actual 996 turbo 75.5 cm² ) had to be extremely soft because of noise issues, thus the friction coefficient was far too low to achieve good deceleration / friction.
As a result of bigger disks and calipers, the gain in weight that was promised is smaller than anybody thought, also because of the
stainless steel ( v4a ) hats where the ceramic discs are bolted to, which are extremly heavy.
Thus the engineers kept running from one problem to the next, ending up with a system that has one advantage, that is if the discs don't brittle, and that is outlast the life span of the car - but who would drive a GT2 for over 300,000 miles?
If you have friction ( and this is what you want and as much as possible ) you create a lot of heat. The heat has to be dissipated to make it possible to create new heat again, at each stop. Thus, you need a material which is suitable to take and dissipate heat. Today, that is still cast iron.
Cast iron can be manufactured, machined, perfectly balanced and so on for a fraction of the cost of ceramic / silicium or carbon discs.
In addition cast iron allows for the use of aluminium hats vs the heavy hats used for ceramic brakes. Cast iron brakes stop, they last and they are much more quiet than carbon or ceramic compounds.
By the way the carbon discs are also only suitable for light race cars, never for heavy street cars. No friction under cold conditions, high wear under extremly hot conditions which is needed to make the carbon brakes work.
The little weight advantage ( who of us actually feels 2-3 kg ) is not worth the problems and trouble that the other solutions provide.
Finally, after reading this who actually still believes that the ceramic brakes were put in because they were so much better than a std. system? I don't, and after trying them and talking with someone who is on the inside of the braking industry, I certainly think that it is a clever way to disguise a partial engineering failure with a clever marketing positioning and a high price.
As soon as we have put on the new brake system (cast iron) on the GT2 we will make some runs around Spa and report.
Gerard
The first and most important one is that ceramic brakes are mostly a marketing plot. Why charge a lot of money for brakes that add a lot of problems while the std Porsche brakes have been known to be the best in the business? To make more money - as simple as that.
According to the engineer these brakes ( ceramic ) will not work the way they should/could because:
Ceramic is an excellent isolator but it does an extremely poor job at absorbing and dissipating heat. The heat generated during heavy braking is not being taken by the ceramic disc. In addition to this, the ventilation is very poor, because it is currently technically impossible to make really sophisticated and "filigrane" vanes with a large surface to dissapate heat quickly from the ceramic disc. This is due to the extremely complicated maufacturing process for ceramic discs.
Thus the heat stays there and goes through the pads to the specially-isolated pistons and into to the fluid. Brake pedal failure is the consequence, which is what I experienced at Spa.
Next, the reason why the ceramic discs are bigger ( 350 mm ) than the stock turbo 996 discs ( 330 mm ) is again only due to temperature. The same holds true for the bigger caliper ( 6-piston ) and the much bigger
pads ( 115 cm² instead of 75.5 cm² ).
The very first pads used with the ceramic disc ( same as the actual 996 turbo 75.5 cm² ) had to be extremely soft because of noise issues, thus the friction coefficient was far too low to achieve good deceleration / friction.
As a result of bigger disks and calipers, the gain in weight that was promised is smaller than anybody thought, also because of the
stainless steel ( v4a ) hats where the ceramic discs are bolted to, which are extremly heavy.
Thus the engineers kept running from one problem to the next, ending up with a system that has one advantage, that is if the discs don't brittle, and that is outlast the life span of the car - but who would drive a GT2 for over 300,000 miles?
If you have friction ( and this is what you want and as much as possible ) you create a lot of heat. The heat has to be dissipated to make it possible to create new heat again, at each stop. Thus, you need a material which is suitable to take and dissipate heat. Today, that is still cast iron.
Cast iron can be manufactured, machined, perfectly balanced and so on for a fraction of the cost of ceramic / silicium or carbon discs.
In addition cast iron allows for the use of aluminium hats vs the heavy hats used for ceramic brakes. Cast iron brakes stop, they last and they are much more quiet than carbon or ceramic compounds.
By the way the carbon discs are also only suitable for light race cars, never for heavy street cars. No friction under cold conditions, high wear under extremly hot conditions which is needed to make the carbon brakes work.
The little weight advantage ( who of us actually feels 2-3 kg ) is not worth the problems and trouble that the other solutions provide.
Finally, after reading this who actually still believes that the ceramic brakes were put in because they were so much better than a std. system? I don't, and after trying them and talking with someone who is on the inside of the braking industry, I certainly think that it is a clever way to disguise a partial engineering failure with a clever marketing positioning and a high price.
As soon as we have put on the new brake system (cast iron) on the GT2 we will make some runs around Spa and report.
Gerard
10-10-2003, 02:17 AM
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Gerard,
Was that engineer asleep during Physics class? What are his exact qualifications? Does he specialize in metals, hydraulics, compounds, thermodynamics or does he know it all?
Riddle me this one?
Porsche is developing the Carrera GT as a showpiece of technology, with no significant limits on spending. They have again chosen to use ceramics on the brakes (and the clutch).
The clutch to improve durability (over Carbon Fibre and to lower rotational mass)
If the decision was technically flawed to use ceramics on the GT2 etc, and all the smart buyers (and engineers) out there are sure to figure it out, why would they compound the error by implementing the technology on the Carrera GT where there are no practical budget constraints? Assume Porsche engineers are smart too and can figure out their mistakes.
They could have simply moved on to another technology and touted it as the latest revolution.
I'll put my trust in Porsche engineers any day...Come to think of it I do, everytime I drive. I think there's a whole more to this than a simplistic "marketing" answer.
For a while this whole issue worried me, but the more I read about it, the less convinced I am about the source of the problems. My own experience (with Ceramic brakes) and observation of others leads me to conclude that they are are not flawed in concept and theory.
Individual problems are not pervasive enough to draw conclusions, but some may have been manufacturing defects and more, most likely improper application. But without exact knowledge on a case by case basis it's impossibe to say.
Was that engineer asleep during Physics class? What are his exact qualifications? Does he specialize in metals, hydraulics, compounds, thermodynamics or does he know it all?
Riddle me this one?
Porsche is developing the Carrera GT as a showpiece of technology, with no significant limits on spending. They have again chosen to use ceramics on the brakes (and the clutch).
The clutch to improve durability (over Carbon Fibre and to lower rotational mass)
If the decision was technically flawed to use ceramics on the GT2 etc, and all the smart buyers (and engineers) out there are sure to figure it out, why would they compound the error by implementing the technology on the Carrera GT where there are no practical budget constraints? Assume Porsche engineers are smart too and can figure out their mistakes.
They could have simply moved on to another technology and touted it as the latest revolution.
I'll put my trust in Porsche engineers any day...Come to think of it I do, everytime I drive. I think there's a whole more to this than a simplistic "marketing" answer.
For a while this whole issue worried me, but the more I read about it, the less convinced I am about the source of the problems. My own experience (with Ceramic brakes) and observation of others leads me to conclude that they are are not flawed in concept and theory.
Individual problems are not pervasive enough to draw conclusions, but some may have been manufacturing defects and more, most likely improper application. But without exact knowledge on a case by case basis it's impossibe to say.
10-10-2003, 02:46 AM
#29
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colm, i totally agree. i do not have a tremendously extensive background in metallurgy and thermodynamics but i assume this "engineer" does not either. I have personally given the PCCB brakes hell on the track with the stock pads none the less and had nothing but outstanding results. My limited knowledge of the technology makes sense to me.
Even if we assume for a second that porsche is screwing the consumer over, how do you account for ferrari using carbon discs on the enzo and challenge stradale? Are we to believe that two of the most outstanding car manufacturers in the world are fleecing consumers and touting poor engineering as breakthrough technology? What do they have to gain?
anyway, too many
and i'm rambling now....
-Steve
Even if we assume for a second that porsche is screwing the consumer over, how do you account for ferrari using carbon discs on the enzo and challenge stradale? Are we to believe that two of the most outstanding car manufacturers in the world are fleecing consumers and touting poor engineering as breakthrough technology? What do they have to gain?
anyway, too many
and i'm rambling now....-Steve
10-10-2003, 08:12 AM
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I did not intend to start a "situation" here 
I just was quite surprised by the brakes I tried on the GT2 in Spa, which prompted a call to the factory, who did not really answer anything that was of interest, as well as a call to two leading brake manufacturers including Brembo. The guy who I have been in touch with is the head of engineering for a competitor of Brembo and YES his company also has a ceramic disk compound (no particular bias), as well as carbon fiber brakes that they codevelop with Carbon Industries in France. I don't know if he was or wasn't asleep during physics class, fact is that in my humble opinion he has a fair knowledge of what he talks about and consults with leading teams as well as manufacturers.
Again I started this thread because of a certain uneaseaness with the product after trying it, and if some of you find the brakes to work - great - my only other point about this being marketing lead and I stand by my opinion is:
Was there a problem with the "normal" Porsche brakes to start with? And if yes (which I doubt) is the gap worth the price asked for PCCB? - this last question was the starting point of the disappointment.
And PLEASE I don't need private mails to be taught on this subject, if there is anything you want to say post it here.
Gerard
I just was quite surprised by the brakes I tried on the GT2 in Spa, which prompted a call to the factory, who did not really answer anything that was of interest, as well as a call to two leading brake manufacturers including Brembo. The guy who I have been in touch with is the head of engineering for a competitor of Brembo and YES his company also has a ceramic disk compound (no particular bias), as well as carbon fiber brakes that they codevelop with Carbon Industries in France. I don't know if he was or wasn't asleep during physics class, fact is that in my humble opinion he has a fair knowledge of what he talks about and consults with leading teams as well as manufacturers.
Again I started this thread because of a certain uneaseaness with the product after trying it, and if some of you find the brakes to work - great - my only other point about this being marketing lead and I stand by my opinion is:
Was there a problem with the "normal" Porsche brakes to start with? And if yes (which I doubt) is the gap worth the price asked for PCCB? - this last question was the starting point of the disappointment.
And PLEASE I don't need private mails to be taught on this subject, if there is anything you want to say post it here.
Gerard