Rear brakes
12-10-2007, 12:35 AM
#1
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Rear brakes
I had the RS at VIR this weekend (great weather and great event) and I checked the temps on the rotors after each session. The rears were always 115 to 165 degrees hotter than the fronts. I have the PCCB's but I put on steel rotors (AP fronts and 997 cup rears) with PAGID RS19 pads. The rear pads were obviously wearing faster than the fronts too.
Keep in mind I had TC turned OFF, so it couldn't have been that causing the rear temps to be higher.
They have obviously tuned the brakes to have much more rear bias. Is this true with the factory steels too? Anyone else have this experience?
Can the bias be adjusted? Is it worth trying?
Besides the brake concern, I have to say that I really enjoyed the RS on the track this time.
It is obviously much softer than the Cup, but it was very fun nonetheless. I ran Hoosier R6's.
The car felt very well balanced. I had the following setup:
-2.8 degrees in front and -2.6 in the rear
0 toe in front and 2mm in the rear.
The car weight was as follows:
With stock wheels, PCCB rotors, 996 GT3 seats, DasSport Bar and about 1/4 tank fuel (I think) it was 3142lbs.
With the steel rotors and 18" Fikse Profil 5S wheels/Hoosier R6's and 2/3 tank fuel it was 3178lbs.
The steel rotors added 34lbs (21.5 each compared to 13 for the PCCB). I have not weighed the wheels/tires to compare, but the 18" Fikse's with R6's are obviously lighter.
Keep in mind I had TC turned OFF, so it couldn't have been that causing the rear temps to be higher.
They have obviously tuned the brakes to have much more rear bias. Is this true with the factory steels too? Anyone else have this experience?
Can the bias be adjusted? Is it worth trying?
Besides the brake concern, I have to say that I really enjoyed the RS on the track this time.
It is obviously much softer than the Cup, but it was very fun nonetheless. I ran Hoosier R6's.
The car felt very well balanced. I had the following setup:
-2.8 degrees in front and -2.6 in the rear
0 toe in front and 2mm in the rear.
The car weight was as follows:
With stock wheels, PCCB rotors, 996 GT3 seats, DasSport Bar and about 1/4 tank fuel (I think) it was 3142lbs.
With the steel rotors and 18" Fikse Profil 5S wheels/Hoosier R6's and 2/3 tank fuel it was 3178lbs.
The steel rotors added 34lbs (21.5 each compared to 13 for the PCCB). I have not weighed the wheels/tires to compare, but the 18" Fikse's with R6's are obviously lighter.
12-10-2007, 01:33 AM
#2
GT3 player par excellence
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i have iron rotors.
the rear and front wear at virtually the same rate where as 996gt3, the front wears 2x faster than front.
i drive with TC off and RS29's
the rear and front wear at virtually the same rate where as 996gt3, the front wears 2x faster than front.
i drive with TC off and RS29's
12-10-2007, 06:28 AM
#3
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Good timing!
I was about to post a comment on rear brake bias. I've just replaced rear pads. It appears they are wearing at twice the rate of the fronts.
To quote Porsche on the subject...
"The distribution of brake power between the front and rear axle has been reconfigured on the new 911 GT3. The rear axle receives a higher level of brake power. This redistribution is based on experience from motor racing and results in additional usage of the brake power on the rear axle at the beginning of braking. A relatively high load applies on the rear axle at this point in time on account of the rear-mounted engine. This is exploited to transfer even greater braking force to the road and to further reduce the braking distance."
I read this to mean that the car has a variable brake bias - bias to the rear at the start of braking then shifting forward progressively.
I was about to post a comment on rear brake bias. I've just replaced rear pads. It appears they are wearing at twice the rate of the fronts.
To quote Porsche on the subject...
"The distribution of brake power between the front and rear axle has been reconfigured on the new 911 GT3. The rear axle receives a higher level of brake power. This redistribution is based on experience from motor racing and results in additional usage of the brake power on the rear axle at the beginning of braking. A relatively high load applies on the rear axle at this point in time on account of the rear-mounted engine. This is exploited to transfer even greater braking force to the road and to further reduce the braking distance."
I read this to mean that the car has a variable brake bias - bias to the rear at the start of braking then shifting forward progressively.
12-10-2007, 11:25 AM
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Just to add that I've heard talk of a caliper problem on the rear too.
Caliper is binding when hot causing the pads to remain in contact with the disc, hence the premature wear.
One successful warranty claim so far here in the UK. The customer drove the car hard and immediately returned to the dealer who put it on a ramp to find the rear wheels were binding.
Anyone else come across this?
Caliper is binding when hot causing the pads to remain in contact with the disc, hence the premature wear.
One successful warranty claim so far here in the UK. The customer drove the car hard and immediately returned to the dealer who put it on a ramp to find the rear wheels were binding.
Anyone else come across this?
12-10-2007, 01:05 PM
#5
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I did about 50 laps of the nordschliefe when I collected my car from the factory back in June, and almost completely wore out a set of rear PCCB pads!
12-10-2007, 11:11 PM
#6
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Steels. My rears are wearing out twice as fast as the fronts. 8 track days and the rear pads are completely worn out. Front rotors are worn out and are going to be replaced before the next event. Using traction control.
12-10-2007, 11:35 PM
#7
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I recently ran my first event(with PCCB) and rear temps were indeed 115 or so higher than fronts. And I was using TC. I would like to change to iron rotors before too long. Would you mind posting the part numbers for the AP and cup rotors for us FNG's?TIA
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12-10-2007, 11:49 PM
#9
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I don't know the part numbers right off. But I got the front AP rotors from CDOC. They are the direct replacements for a 997 Cup. The rears are direct from a 997 Cup. I got those from Austin at TRG.
12-11-2007, 12:39 AM
#10
I have the same brake setup that you do...
Except I have GT2 brake cooling scoops on the front, yes, they do scape a bit because they are larger. The high perfomance guys at Napleton built some custom scoops on the brake cooling holes for the rear brakes and it does help.
Except I have GT2 brake cooling scoops on the front, yes, they do scape a bit because they are larger. The high perfomance guys at Napleton built some custom scoops on the brake cooling holes for the rear brakes and it does help.
12-11-2007, 01:17 AM
#11
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Any value to using different pad densities front/rear? It was suggested to me to do this. They also suggested it was part of the cause of my rear shimmy under hard braking.
Mario
Mario
12-11-2007, 09:30 AM
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I had the RS at VIR this weekend (great weather and great event) and I checked the temps on the rotors after each session. The rears were always 115 to 165 degrees hotter than the fronts. I have the PCCB's but I put on steel rotors (AP fronts and 997 cup rears) with PAGID RS19 pads. The rear pads were obviously wearing faster than the fronts too.
Keep in mind I had TC turned OFF, so it couldn't have been that causing the rear temps to be higher.
They have obviously tuned the brakes to have much more rear bias. Is this true with the factory steels too? Anyone else have this experience?
Can the bias be adjusted? Is it worth trying?
Besides the brake concern, I have to say that I really enjoyed the RS on the track this time.
It is obviously much softer than the Cup, but it was very fun nonetheless. I ran Hoosier R6's.
The car felt very well balanced. I had the following setup:
-2.8 degrees in front and -2.6 in the rear
0 toe in front and 2mm in the rear.
The car weight was as follows:
With stock wheels, PCCB rotors, 996 GT3 seats, DasSport Bar and about 1/4 tank fuel (I think) it was 3142lbs.
With the steel rotors and 18" Fikse Profil 5S wheels/Hoosier R6's and 2/3 tank fuel it was 3178lbs.
The steel rotors added 34lbs (21.5 each compared to 13 for the PCCB). I have not weighed the wheels/tires to compare, but the 18" Fikse's with R6's are obviously lighter.
Keep in mind I had TC turned OFF, so it couldn't have been that causing the rear temps to be higher.
They have obviously tuned the brakes to have much more rear bias. Is this true with the factory steels too? Anyone else have this experience?
Can the bias be adjusted? Is it worth trying?
Besides the brake concern, I have to say that I really enjoyed the RS on the track this time.
It is obviously much softer than the Cup, but it was very fun nonetheless. I ran Hoosier R6's.
The car felt very well balanced. I had the following setup:
-2.8 degrees in front and -2.6 in the rear
0 toe in front and 2mm in the rear.
The car weight was as follows:
With stock wheels, PCCB rotors, 996 GT3 seats, DasSport Bar and about 1/4 tank fuel (I think) it was 3142lbs.
With the steel rotors and 18" Fikse Profil 5S wheels/Hoosier R6's and 2/3 tank fuel it was 3178lbs.
The steel rotors added 34lbs (21.5 each compared to 13 for the PCCB). I have not weighed the wheels/tires to compare, but the 18" Fikse's with R6's are obviously lighter.
...chasing Matt in his RS at VIR http://www.youtube.com/watch?v=jY8VH9lJtTk
12-11-2007, 12:53 PM
#15
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I *DO NOT* recommend running on the track with TC engaged *unless* it is wet ...