Track Day with PCCB: No Problem, But ?
03-28-2005, 12:07 AM
#16
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Originally Posted by C4S Surgeon
RJ, are you getting a black on black GT3? My brother(DJ996) in H town has a friend who jut ordered such a car, he's extremely jealous!
03-28-2005, 12:12 AM
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Originally Posted by Bob Rouleau
A few observations:
Gen 1 PCCB become unusable due to excess heat and or a lack of cooling,
ABS may contribute to overheating but there is no evidence of this that I know of.
Porsche changed the Yellow "Sport" pads last year. The new compostion is a different color although still called "Yellow". I think I heard that thaey are black and white (striped) but I am not sure.
PCCB will last longer if you try and cool them after each session.
PCCB will last longer if you replace pads before they are 50 percent used. Thicker pads absorb more heat and help prevent overheating the rotors.
Gen 1 PCCB will last a long time if you replace them with steel rotors like I did.
Rgds,
Gen 1 PCCB become unusable due to excess heat and or a lack of cooling,
ABS may contribute to overheating but there is no evidence of this that I know of.
Porsche changed the Yellow "Sport" pads last year. The new compostion is a different color although still called "Yellow". I think I heard that thaey are black and white (striped) but I am not sure.
PCCB will last longer if you try and cool them after each session.
PCCB will last longer if you replace pads before they are 50 percent used. Thicker pads absorb more heat and help prevent overheating the rotors.
Gen 1 PCCB will last a long time if you replace them with steel rotors like I did.
Rgds,
According to an informed mechanic at my dealer, he says the biggest reliability issue is with ABS pounding the unloaded wheel while trail-braking into a corner.
He doesn't think the heat is an issue by itself.
I did notice that by softening the front bar and stiffening the rear bar one could reduce the unloading of the front wheels, however this setup will
cause more oversteer (at a very simple estimation) without a spring rate change.
Having said that, as soon as the rear calipers arrive my car is
going back to metal discs as well.
Even if I can make these ceramics last 20K miles, the replacement cost is prohibitive over the long term.
And if Porsche ever comes out with $1K/disc replacements, then
I would be happy to put the discs back on.
Last edited by bora; 03-28-2005 at 03:34 AM.
03-28-2005, 12:41 AM
#19
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Originally Posted by Jack
As an aside, according to the F-car tech, it's the number of heat cycles (not external wear) that determines when the 360 CS carbon rotors are due for replacement -- the CS computer measures this factor.
03-28-2005, 01:03 AM
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Jack,
While allowing for the possibility of error on my part as well, I know that the conventional wisdom on this site maintains that the ceramic failure is an "over-heating" issue and while this is possible it is more likely to be a "force" issue.
Remember what happens to a ceramic disc if you hit it with the wheel when changing it (chips or shatters), well it appears the ABS can inflict the same damage.
If it were purely a overheating issue then Porsche would, more likely, have caught it with their test drivers when testing. However, if it were an ABS issue, then since their drivers were less likely to bo using ABS heavily (based upon my PDE and Leipzig experiences) then it is possible that this went unnoticed.
Most likely the composition of the new disc has a better structural rigidity, based on shorter fibers, and with any new braking system they will always improve the air flow when they can.
Now what would be interesting to really understand would be the effect of a similar impact on a hot and cold disc..less or more damage?
While allowing for the possibility of error on my part as well, I know that the conventional wisdom on this site maintains that the ceramic failure is an "over-heating" issue and while this is possible it is more likely to be a "force" issue.
Remember what happens to a ceramic disc if you hit it with the wheel when changing it (chips or shatters), well it appears the ABS can inflict the same damage.
If it were purely a overheating issue then Porsche would, more likely, have caught it with their test drivers when testing. However, if it were an ABS issue, then since their drivers were less likely to bo using ABS heavily (based upon my PDE and Leipzig experiences) then it is possible that this went unnoticed.
Most likely the composition of the new disc has a better structural rigidity, based on shorter fibers, and with any new braking system they will always improve the air flow when they can.
Now what would be interesting to really understand would be the effect of a similar impact on a hot and cold disc..less or more damage?
03-28-2005, 04:31 AM
#21
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Originally Posted by DonneyJ
After you've finished tracking have a short slow drive trying not to use the brakes to cool em down and then park up in gear without the handbrake on. (source Porsche PDE instructor)
03-28-2005, 07:53 AM
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Originally Posted by 03-turbo911
That is excellent advice. I couldn't belive how many people just come back from a session without a proper cool-down lap and just engage their parking brakes!
03-28-2005, 11:17 AM
#23
Originally Posted by bora
According to an informed mechanic at my dealer, he says the biggest reliability issue is with ABS pounding the unloaded wheel while trail-braking into a corner.
He doesn't think the heat is an issue by itself.
He doesn't think the heat is an issue by itself.
As this has been posted multiple times, PCCB failures may vary with the kind of pad used (green pads are especially hard on rotors), how hard on brakes the track / driver is, and how long the car is driven without cooling.
Usually, the pad separates from the backing plate. I had no problem with mine at Laguna until I ran non-stop for an hour, at which point one pad almost lost all of its material.
That did not destroy the rotors. Just the pad and my trust toward this system at the track.
Arnaud
03-28-2005, 11:56 AM
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Arnaud,
As far as I know, you can see this on TV with F1 and other forms of racing all the time.
While trying to use the brakes and turn at the same time, one
side of the car is lighter and the wheel is slightly off the ground,
thereby rotating at a different speed or not at all (extreme case)
and ABS computer interprets this as lock-up and engages.
In F1, this shows up as tell-tale smoke from the unloaded wheel.
As far as I know, you can see this on TV with F1 and other forms of racing all the time.
While trying to use the brakes and turn at the same time, one
side of the car is lighter and the wheel is slightly off the ground,
thereby rotating at a different speed or not at all (extreme case)
and ABS computer interprets this as lock-up and engages.
In F1, this shows up as tell-tale smoke from the unloaded wheel.
Originally Posted by AW
This does not make sense to me. At least the trailbraking part. Trailbraking is a smooth transition from full braking to progressively turning while releasing the brake. With what he describes, the car needs to be sufficiently turning such as one front wheel is unloaded, yet braking is hard enough to trigger ABS. Maybe I'm missing something but I really cannot see how it could happen, unless the driver releases the brakes too slowly, which will cause the car to spin anyhow. Am I missing something?
As this has been posted multiple times, PCCB failures may vary with the kind of pad used (green pads are especially hard on rotors), how hard on brakes the track / driver is, and how long the car is driven without cooling.
Usually, the pad separates from the backing plate. I had no problem with mine at Laguna until I ran non-stop for an hour, at which point one pad almost lost all of its material.
That did not destroy the rotors. Just the pad and my trust toward this system at the track.
Arnaud
As this has been posted multiple times, PCCB failures may vary with the kind of pad used (green pads are especially hard on rotors), how hard on brakes the track / driver is, and how long the car is driven without cooling.
Usually, the pad separates from the backing plate. I had no problem with mine at Laguna until I ran non-stop for an hour, at which point one pad almost lost all of its material.
That did not destroy the rotors. Just the pad and my trust toward this system at the track.
Arnaud
03-28-2005, 01:47 PM
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Originally Posted by Jack
Also, it seems the "green" racing pads can really cause premature PCCB rotor damage (due to pad destruction and the resultant metal to ceramic contact) or so I've been told. Who knows the real story???
980 351 939 00 (front)
996 352 947 03 (rear)
The pads are black with no stripes that I can see. I'm on my 4th set after one year and about 25 track days. The front rotors are starting to show some "wear", rears look the same as when new.
I'm very careful about cool down and cleaning the cooling holes. However I have no unrealistic expecatations. The jury is still out for me -despite other experinces expressed here I will be my own judge. I contine to change pads when they are 50 to 60% worn which is probably the best advice I have had about the brakes.
The GREEN pads are the Motorsport pad and Porsche has expressed to me in no uncertain terms that warrenty will NOT apply to the brakes or pads should those pads be used at anytime. I ha dto wonder why they offer them and on the TSB they even state that they are for "track use".
03-28-2005, 04:07 PM
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4Kurves - thanks for the clarification aboout the new version yellow pads which aren't yellow.
Bora - regarding trail braking - F1 cars have such tremendous down force that it is almost impossible to lock up a wheel braking at high speed. On the other hand the inside wheel is less loaded and it is not unusual to see a minor lock up and a puff of smoke since that wheel does not have as much weight on it. I also agree that F1 cars trail brake, many drivers complain of serious understeer and trail braking is a good technique to overcome that handling problem.
AW correctly points out that trail-braking is a very smooth transition off the brakes during and after turn-in. I defy anyone to make his 911 turn in properly while ABS is operating. When I have made this mistake, my cars (GT2, GT3) will NOT turn in and I end up going wide (and slow). I got caught by a sudden rain shower which wet one part of the track and not the rest. I was glad to have ABS but I blew the corner badly.
Some drivers will use ABS (in a straight line) initially followed by a fast reduction of pressure to get to threshold braking. I do not endorse the technique myself but some 911 drivers use it.
Colm (who is a very smart guy) has reasons to believe ABS shortens rotor life. He is probably right, although I can't say one way or the other since I avoid ABS as much as possible.
Note that there have been failures of PCCB on 996 Turbos as well. You cannot trail brake a 996TT since Yaw-Control (which cannot be disabled) prevents you from doing so - rather violently prevents you, I might add. On the other hand a lack of finesse can certainly invoke ABS under harsh braking.
Regards,
Bora - regarding trail braking - F1 cars have such tremendous down force that it is almost impossible to lock up a wheel braking at high speed. On the other hand the inside wheel is less loaded and it is not unusual to see a minor lock up and a puff of smoke since that wheel does not have as much weight on it. I also agree that F1 cars trail brake, many drivers complain of serious understeer and trail braking is a good technique to overcome that handling problem.
AW correctly points out that trail-braking is a very smooth transition off the brakes during and after turn-in. I defy anyone to make his 911 turn in properly while ABS is operating. When I have made this mistake, my cars (GT2, GT3) will NOT turn in and I end up going wide (and slow). I got caught by a sudden rain shower which wet one part of the track and not the rest. I was glad to have ABS but I blew the corner badly.
Some drivers will use ABS (in a straight line) initially followed by a fast reduction of pressure to get to threshold braking. I do not endorse the technique myself but some 911 drivers use it.
Colm (who is a very smart guy) has reasons to believe ABS shortens rotor life. He is probably right, although I can't say one way or the other since I avoid ABS as much as possible.
Note that there have been failures of PCCB on 996 Turbos as well. You cannot trail brake a 996TT since Yaw-Control (which cannot be disabled) prevents you from doing so - rather violently prevents you, I might add. On the other hand a lack of finesse can certainly invoke ABS under harsh braking.
Regards,
03-28-2005, 05:03 PM
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Bill C4S - Not sure I understand your question. I am pro threshold braking, how could I not be 
I prefer not to get find the threshold by invoking ABS and then backing off a bit. I am confident that I can brake in a shorter distance by not triggering ABS at all.
I also endorse trail-braking a 911 in slow corners because a well sorted car will understeer in slow corners so as to be neutral in fast ones.
I am probably a bit dense today so, please elaborate on your question.
Best,
I prefer not to get find the threshold by invoking ABS and then backing off a bit. I am confident that I can brake in a shorter distance by not triggering ABS at all. I also endorse trail-braking a 911 in slow corners because a well sorted car will understeer in slow corners so as to be neutral in fast ones.
I am probably a bit dense today so, please elaborate on your question.
Best,
