997 GT2 PCCB Failure (brakes melt)
05-26-2009, 07:15 PM
#46
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Appears you are heat treating with phase change the calipers/pads and potentially rotors. Witness the paint colour change, and friability of the pads.
I'd guess temps approaching 1000F...which for a street pad would suggest constant friction between pad and rotor.
My concern would be catastrophic failure at the worst possible moment....
Getting a GT2 brake system expert - Porsche Motorsports NA? - to diagnose the system would be my first port of call.
I'd guess temps approaching 1000F...which for a street pad would suggest constant friction between pad and rotor.
My concern would be catastrophic failure at the worst possible moment....
Getting a GT2 brake system expert - Porsche Motorsports NA? - to diagnose the system would be my first port of call.
05-26-2009, 07:20 PM
#47
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Thread Starter
Bob, My 997 RS has over 50 track days. Front rotors replaced early this season. Rears are still original. Traction Control and a heavy right foot are the usual reason for premature rear pad/rotor problems.
In our local region the are a dozen 997Gt3s (most white!) and since turning off TC no issues. Same with a 997GT2, owner wore our rear PCCB in less than 3,000 miles. TC and his brutal driving style were the culprit. He was shown how to accelerate progressively and his rotor wear has gone back to normal.
The brake bias on the 997 is far superior to the 996 which had the fronts doing ALL the work. We used to use RS 19 in front and RS 14 in back to help balance the braking. It worked on the 996 GT3.
Neros must have a problem - sticking master cylinder maybe? FWIW, and youoprobably know better than I, a couple of locals have swapped their expensive PCCB rotors for iron ones from the Cup Car - a direct bolt on and far cheaper to replace than PCCB.
Best,
In our local region the are a dozen 997Gt3s (most white!) and since turning off TC no issues. Same with a 997GT2, owner wore our rear PCCB in less than 3,000 miles. TC and his brutal driving style were the culprit. He was shown how to accelerate progressively and his rotor wear has gone back to normal.
The brake bias on the 997 is far superior to the 996 which had the fronts doing ALL the work. We used to use RS 19 in front and RS 14 in back to help balance the braking. It worked on the 996 GT3.
Neros must have a problem - sticking master cylinder maybe? FWIW, and youoprobably know better than I, a couple of locals have swapped their expensive PCCB rotors for iron ones from the Cup Car - a direct bolt on and far cheaper to replace than PCCB.
Best,
05-26-2009, 08:29 PM
#48
Drifting
Nero, another thought would be to get an infrared temp gauge and to compare temps with you driving the car and with a local fast driver. I noticed very high rear temps on my GT3 when it was new and I was using the TC on a local, tight, twisty and bumpy track. The car was constantly into TC even though the light was not on and the car didn't feel restricted. I went through half a set of rear pads in one day. Once I turned TC off, no more excessive rear pad wear.
I agree with you that the car should be drivable in any fashion you want, given that it's a GT2 and you're using the factory components, but we have to be reasonable in our expectations given that it is being used on a racetrack and under severe stress. Rather than fight the systems, try running with TC and SC off and then report back if you're still getting the same problems.
I agree with you that the car should be drivable in any fashion you want, given that it's a GT2 and you're using the factory components, but we have to be reasonable in our expectations given that it is being used on a racetrack and under severe stress. Rather than fight the systems, try running with TC and SC off and then report back if you're still getting the same problems.
05-26-2009, 08:42 PM
#49
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I see a new problem, which is a consequence of the first one.
With PCCB (applies to cast iron rotors as well, but they don't fall apart in chunks), running brake pads beyond 50% of life left creates this second problem. The brake pad starts to fall apart in chunks, and it becomes really abrasive on the rotors, it also reduces its ability to dissipate heat. You can feel how abrasive the pads are when they reach this stage just by rubbing your hands on them.
The chunks on the rotors seem to be related to the rear brake pads coming to an end, and most likely the rear rotors and calipers were running hotter than usual due to the thin pads, hence the paint dis-coloration and melted rubber boots in the caliper. Back in 2002, a few GT2 owners got to destroy their PCCB rotors by running the stock pads beyond usable life.
If Porsche won't take the tab on the fix (I doubt they will), just get the calipers rebuilt (PCNA has the caliper rebuild kits). Put the 997 Gt3 Cup rotors, and run a harder pad on the front (RS-15) and RS29 in the back. This will change bias as a factor of more bite in the front.
Ultimately, it won't fix the problem with TC coming on even with the switch set to Off.
I insist there is something weird, because we have plenty of track miles with the 997 GT3/GT3 RS and haven't seen something like this. I know the GT2 is faster and it's braking from higher speeds, but I have run with slicks in the GT3 RS at a decent pace, and have yet to experience that kind of overheating. I ran my 997 GT3 RS with PCCB (old generation) and RS29 pads. It worked quite well.
With PCCB (applies to cast iron rotors as well, but they don't fall apart in chunks), running brake pads beyond 50% of life left creates this second problem. The brake pad starts to fall apart in chunks, and it becomes really abrasive on the rotors, it also reduces its ability to dissipate heat. You can feel how abrasive the pads are when they reach this stage just by rubbing your hands on them.
The chunks on the rotors seem to be related to the rear brake pads coming to an end, and most likely the rear rotors and calipers were running hotter than usual due to the thin pads, hence the paint dis-coloration and melted rubber boots in the caliper. Back in 2002, a few GT2 owners got to destroy their PCCB rotors by running the stock pads beyond usable life.
If Porsche won't take the tab on the fix (I doubt they will), just get the calipers rebuilt (PCNA has the caliper rebuild kits). Put the 997 Gt3 Cup rotors, and run a harder pad on the front (RS-15) and RS29 in the back. This will change bias as a factor of more bite in the front.
Ultimately, it won't fix the problem with TC coming on even with the switch set to Off.
I insist there is something weird, because we have plenty of track miles with the 997 GT3/GT3 RS and haven't seen something like this. I know the GT2 is faster and it's braking from higher speeds, but I have run with slicks in the GT3 RS at a decent pace, and have yet to experience that kind of overheating. I ran my 997 GT3 RS with PCCB (old generation) and RS29 pads. It worked quite well.
05-26-2009, 08:43 PM
#50
Three Wheelin'
Just to correct something, this is the Second time this has happened but the car will have the Third set of brakes in 2,500 miles...
I have yet to see any mention of CBC anywhere (in fact all manuals say the GT2 is one of the only cars where you have complete control after traction control is off) but the Porsche Shop Foreman confirmed that even though traction control is off, he was told by Porsche that it does still kick in if it feels the tires spinning
I have yet to see any mention of CBC anywhere (in fact all manuals say the GT2 is one of the only cars where you have complete control after traction control is off) but the Porsche Shop Foreman confirmed that even though traction control is off, he was told by Porsche that it does still kick in if it feels the tires spinning
05-26-2009, 08:53 PM
#51
Rennlist Member
I did. I had one track day on them and it ate through 50%. That day it ate through the remaining 50% and the calipers! I would have never expected the pads to last 2 track days only. I would love to just replace them with the GTR brakes from Brembo but there is a risk that this is a traction control issue where the rears will still be pulsed all the time and the new brakes might also overheat and then I have 2 brakes that don't work. I also don't want to completely disable traction control because I appreciate the help of ABS during braking.
In your case where you are obviously a competent track driver, to avoid toasting the brakes, you should be switching off both the SC and SC+TC buttons! Even when both are off ABS will work without a problem.
ABS is NOT a defeatable system and will always be there to assist even when both SC and TC are switched off (unless you were able to pull a fuse for it, that is). It will assist on braking but not acceleration which is obviously where this level of damage must be occuring...
If you are leaving the SC+TC button active (thinking it runs ABS) it would be pulsing your rears on acceleration and this would be slaughtering your brakes with 530hp at the other end.....
Switch of both aids and feed power progressively to avoid traction loss on acceleration....
ps. CBC assumming it exists would not be your problem as from the descriptions given, it alters braking on individual wheels whilst you are braking to control spin! It is NOT doing additional braking when you are off the pedal.... If this were the problem, it would indicate you are overdoing the braking....
05-26-2009, 08:57 PM
#52
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I was told that I needed to change my driving style as well to be smoother on the throttle to avoid the brakes pulsing the rears. My response was that if I want to push the car to the limits, I am being told I can't because the brakes will fail and it could be at any moment making the car extremely dangerous on the track. You simply never know when you will go to brake and there will be nothing there. Basically it means I can never drive the car on the track again since its a huge risk. How do I know what the limit is until I reach it? (and hopefully the car and me will be fine when I reach the limit again-knock on wood)
Have you ever considered hiring a pro driving coach?
Like: David Murry, Chris Hall, Andrew Davis, Cass Whitehead, Daniel Eastman
Could be an very enlightening experience.
In many cases "smoother" = faster!
Manhandling the car is not necessarily the best way to get to the cars limits.
Driving the car fast is also knowing how to preserve the car
Attend the Legends class offered by PSDS and get tutelage
from:
Hurley Haywood
Vic Elford
Brian Redman
Derek Bell
Patrick Long
05-26-2009, 09:01 PM
#53
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Thread Starter
Nero, another thought would be to get an infrared temp gauge and to compare temps with you driving the car and with a local fast driver. I noticed very high rear temps on my GT3 when it was new and I was using the TC on a local, tight, twisty and bumpy track. The car was constantly into TC even though the light was not on and the car didn't feel restricted. I went through half a set of rear pads in one day. Once I turned TC off, no more excessive rear pad wear.
I agree with you that the car should be drivable in any fashion you want, given that it's a GT2 and you're using the factory components, but we have to be reasonable in our expectations given that it is being used on a racetrack and under severe stress. Rather than fight the systems, try running with TC and SC off and then report back if you're still getting the same problems.
I agree with you that the car should be drivable in any fashion you want, given that it's a GT2 and you're using the factory components, but we have to be reasonable in our expectations given that it is being used on a racetrack and under severe stress. Rather than fight the systems, try running with TC and SC off and then report back if you're still getting the same problems.
05-26-2009, 09:04 PM
#54
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Thread Starter
Neros, you mentioned you do not want to completely disable TC because you appreciate the help of ABS during braking.... What exactly are you switching off????
In your case where you are obviously a competent track driver, to avoid toasting the brakes, you should be switching off both the SC and SC+TC buttons! Even when both are off ABS will work without a problem.
ABS is NOT a defeatable system and will always be there to assist even when both SC and TC are switched off (unless you were able to pull a fuse for it, that is). It will assist on braking but not acceleration which is obviously where this level of damage must be occuring...
If you are leaving the SC+TC button active (thinking it runs ABS) it would be pulsing your rears on acceleration and this would be slaughtering your brakes with 530hp at the other end.....
Switch of both aids and feed power progressively to avoid traction loss on acceleration....
ps. CBC assumming it exists would not be your problem as from the descriptions given, it alters braking on individual wheels whilst you are braking to control spin! It is NOT doing additional braking when you are off the pedal.... If this were the problem, it would indicate you are overdoing the braking....
In your case where you are obviously a competent track driver, to avoid toasting the brakes, you should be switching off both the SC and SC+TC buttons! Even when both are off ABS will work without a problem.
ABS is NOT a defeatable system and will always be there to assist even when both SC and TC are switched off (unless you were able to pull a fuse for it, that is). It will assist on braking but not acceleration which is obviously where this level of damage must be occuring...
If you are leaving the SC+TC button active (thinking it runs ABS) it would be pulsing your rears on acceleration and this would be slaughtering your brakes with 530hp at the other end.....
Switch of both aids and feed power progressively to avoid traction loss on acceleration....
ps. CBC assumming it exists would not be your problem as from the descriptions given, it alters braking on individual wheels whilst you are braking to control spin! It is NOT doing additional braking when you are off the pedal.... If this were the problem, it would indicate you are overdoing the braking....
05-26-2009, 09:10 PM
#56
Advanced
Thread Starter
Perhaps you do need to alter your driving style...
Have you ever considered hiring a pro driving coach?
Like: David Murry, Chris Hall, Andrew Davis, Cass Whitehead, Daniel Eastman
Could be an very enlightening experience.
In many cases "smoother" = faster!
Manhandling the car is not necessarily the best way to get to the cars limits.
Driving the car fast is also knowing how to preserve the car
Attend the Legends class offered by PSDS and get tutelage
from:
Hurley Haywood
Vic Elford
Brian Redman
Derek Bell
Patrick Long
Have you ever considered hiring a pro driving coach?
Like: David Murry, Chris Hall, Andrew Davis, Cass Whitehead, Daniel Eastman
Could be an very enlightening experience.
In many cases "smoother" = faster!
Manhandling the car is not necessarily the best way to get to the cars limits.
Driving the car fast is also knowing how to preserve the car
Attend the Legends class offered by PSDS and get tutelage
from:
Hurley Haywood
Vic Elford
Brian Redman
Derek Bell
Patrick Long
05-26-2009, 09:29 PM
#57
Drifting
05-26-2009, 10:50 PM
#58
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rear brake cooking issues have popped up a few times in the 997/tt/gt3/gt2 spectrum. I for one doubt that the TC (or whatever moniker Porsche gives it) can be fully disabled in any variant. I think that the cases that have seen massive failures - loss of braking, heat, crumbling, etc. are related to overdriving the car and the car is constantly applying the rears to re-stabilize. The GT2 and GT3 are not that heavy, and have pretty decent cooling for the brakes. There is no way it could cook the brakes unless they were always active.
05-27-2009, 12:33 AM
#59
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I have been following this thread for a while, and things are just not adding up.
This thread is almost useless, not because there is not good information or insight, but because without actual observation it is impossible to determine the root cause.
It is like calling a doctor and asking for a diagnosis over the phone, easy (for him) to make assumptions and arrive at the wrong conclusions.
Many will use your post to confirm a bias against PCCB; but it flies in the face of "observed" experience by very professional drivers (Pobst included).
There are apparent contradictions re your statements about switching traction control off, (and see above)... without being there and observing the happenings it is a fools errand to try and guess because there are so many variables.
It is understandable that you are upset but to put the blame on Porsche seems like a pretty big stretch at this point.
Again, if it is just me that is confused then I apologize.
This thread is almost useless, not because there is not good information or insight, but because without actual observation it is impossible to determine the root cause.
It is like calling a doctor and asking for a diagnosis over the phone, easy (for him) to make assumptions and arrive at the wrong conclusions.
Many will use your post to confirm a bias against PCCB; but it flies in the face of "observed" experience by very professional drivers (Pobst included).
There are apparent contradictions re your statements about switching traction control off, (and see above)... without being there and observing the happenings it is a fools errand to try and guess because there are so many variables.
It is understandable that you are upset but to put the blame on Porsche seems like a pretty big stretch at this point.
Again, if it is just me that is confused then I apologize.
05-27-2009, 01:54 AM
#60
Race Director
I have been following this thread for a while, and things are just not adding up.
This thread is almost useless, not because there is not good information or insight, but because without actual observation it is impossible to determine the root cause.
It is like calling a doctor and asking for a diagnosis over the phone, easy (for him) to make assumptions and arrive at the wrong conclusions.
Many will use your post to confirm a bias against PCCB; but it flies in the face of "observed" experience by very professional drivers (Pobst included).
There are apparent contradictions re your statements about switching traction control off, (and see above)... without being there and observing the happenings it is a fools errand to try and guess because there are so many variables.
It is understandable that you are upset but to put the blame on Porsche seems like a pretty big stretch at this point.
Again, if it is just me that is confused then I apologize.
This thread is almost useless, not because there is not good information or insight, but because without actual observation it is impossible to determine the root cause.
It is like calling a doctor and asking for a diagnosis over the phone, easy (for him) to make assumptions and arrive at the wrong conclusions.
Many will use your post to confirm a bias against PCCB; but it flies in the face of "observed" experience by very professional drivers (Pobst included).
There are apparent contradictions re your statements about switching traction control off, (and see above)... without being there and observing the happenings it is a fools errand to try and guess because there are so many variables.
It is understandable that you are upset but to put the blame on Porsche seems like a pretty big stretch at this point.
Again, if it is just me that is confused then I apologize.