Warped discs on a GT3 - braking technique?
Discussion
Workshop tells me my Mk2's discs are very slightly warped as a result of my last track day, and apparently they can solve the problem of grumbling pads and maintain braking performance by cutting a "V" into the pads. Sounds an unusual solution, but they assure me there's no need to change discs - I am no expert and they're not charging me for new discs, so no complaints.
Just a quick question: I have seen plenty of discussion on brake performance on the Mk1 but have not heard of warped discs on the Mk2 due to excessive heat. Am I doing something wrong?
By the end of the last track day I was stamping on the brakes, heel and toeing, and immediately coming off before turning in, so my time on the brake pedal was short but violent. Was this the wrong technique?
I suspect some of the problems on the Mk1 were as a result of braking over a longer period of time before turning in, so I thought my technique was the correct one for the track.
Just a quick question: I have seen plenty of discussion on brake performance on the Mk1 but have not heard of warped discs on the Mk2 due to excessive heat. Am I doing something wrong?
By the end of the last track day I was stamping on the brakes, heel and toeing, and immediately coming off before turning in, so my time on the brake pedal was short but violent. Was this the wrong technique?
I suspect some of the problems on the Mk1 were as a result of braking over a longer period of time before turning in, so I thought my technique was the correct one for the track.
I'm on my 2nd set of discs and pads for my MKII now as the last ones had cracks from all of the holes, this in itself is not unusual on GT3 brakes but should be monitored so that when they get too bad, they must be changed.
The main cause for the cracking is the lack of cooling down time spent on lap getting air to them to cool down rather than coming back in and letting the fry in there own heat !!
I have done over a dozen trackdays in it now, and have never warped the discs, and most of those days were hot summer days too.
From what you say read, your technique sounds about right as the shorter the time you spend on the brakes the better.
Are you tracking it in the emirates, as the much higher temeratures could well be the cause in that case ??
The main cause for the cracking is the lack of cooling down time spent on lap getting air to them to cool down rather than coming back in and letting the fry in there own heat !!
I have done over a dozen trackdays in it now, and have never warped the discs, and most of those days were hot summer days too.
From what you say read, your technique sounds about right as the shorter the time you spend on the brakes the better.
Are you tracking it in the emirates, as the much higher temeratures could well be the cause in that case ??
Last year I warped my discs a little.
An meister told me (I was at the Ring) that I had clearly got the brakes hot and then stopped with my foot on the brake pedal (as in holding the car at a standstill with the foot brake rather than the handbrake). I didn't actually remember doing that, but, whatever.
He told me to (I was at the Nurburgring) do a very hot lap - braking really heavily, getting the brakes really hot - and then after 3/4 of a lap (6 minutes) complete the lap without touching the brakes at all.
It worked - the discs were unwarped.
This was with standard (964RS) disks and Pagid Yellow pads.
I'm now even more especially careful to never hold the car stationary with the foot brake - even on normal road driving.
An meister told me (I was at the Ring) that I had clearly got the brakes hot and then stopped with my foot on the brake pedal (as in holding the car at a standstill with the foot brake rather than the handbrake). I didn't actually remember doing that, but, whatever.
He told me to (I was at the Nurburgring) do a very hot lap - braking really heavily, getting the brakes really hot - and then after 3/4 of a lap (6 minutes) complete the lap without touching the brakes at all.
It worked - the discs were unwarped.
This was with standard (964RS) disks and Pagid Yellow pads.
I'm now even more especially careful to never hold the car stationary with the foot brake - even on normal road driving.
Joe911 said:
I'm now even more especially careful to never hold the car stationary with the foot brake - even on normal road driving.
This is good advice, after I warped by brakes on track last year I spoke at length to a bloke from Performance Friction when sourcing replacements. He told me that he has seen warping happen a few times on the public road when people come down a motorway slipramp at 80-100mph + and brake long and firm to a stop - this generates a lot of heat in the pad - and they then stop at the junction at the bottom of the slipramp with their foot on the brake pedal - this is enough to warp the (apparently) fragile discs we put on our porkers.
Joe911 said:
Last year I warped my discs a little.
An meister told me (I was at the Ring) that I had clearly got the brakes hot and then stopped with my foot on the brake pedal (as in holding the car at a standstill with the foot brake rather than the handbrake). I didn't actually remember doing that, but, whatever.
He told me to (I was at the Nurburgring) do a very hot lap - braking really heavily, getting the brakes really hot - and then after 3/4 of a lap (6 minutes) complete the lap without touching the brakes at all.
It worked - the discs were unwarped.
This was with standard (964RS) disks and Pagid Yellow pads.
I'm now even more especially careful to never hold the car stationary with the foot brake - even on normal road driving.
Isn't this because the discs aren't actually "warped" at all? As I understand it it is due to an uneven deposit of brake pad material onto the disc - usually caused by leaving hot pads in contact with the disc.
And the method you've described above is exactly how I understood that problem to be alleviated.
Don said:
Isn't this because the discs aren't actually "warped" at all? As I understand it it is due to an uneven deposit of brake pad material onto the disc - usually caused by leaving hot pads in contact with the disc.
And the method you've described above is exactly how I understood that problem to be alleviated.
Yes, apparently almost impossible to actually warp the disc itself - good article here:
www.stoptech.com/whitepapers/warped_rotors_myth.htm
Don said:That's my understanding too; "warping" is a myth - see here
Last year I warped my discs a little.
An meister told me (I was at the Ring) that I had clearly got the brakes hot and then stopped with my foot on the brake pedal (as in holding the car at a standstill with the foot brake rather than the handbrake). I didn't actually remember doing that, but, whatever.
He told me to (I was at the Nurburgring) do a very hot lap - braking really heavily, getting the brakes really hot - and then after 3/4 of a lap (6 minutes) complete the lap without touching the brakes at all.
It worked - the discs were unwarped.
This was with standard (964RS) disks and Pagid Yellow pads.
I'm now even more especially careful to never hold the car stationary with the foot brake - even on normal road driving.
Isn't this because the discs aren't actually "warped" at all? As I understand it it is due to an uneven deposit of brake pad material onto the disc - usually caused by leaving hot pads in contact with the disc.
And the method you've described above is exactly how I understood that problem to be alleviated.
www.stoptech.com/whitepapers/warped_rotors_myth.htm
I have read about the so-called "warped discs myth" before. I agree that pad transfer onto the discs can cause juddering under braking and the way to cure this is to do some heavy sharp braking for a couple of laps and then cruise in on a cool down lap not using the brakes. This clears all the pad material off the discs and you should be fine. It has happened to me on track days loads of times.
However, I still think that disc warping can occur as well. I have heard plenty of people say that they have had their discs inspected and they have been found to be warped.
For what its worth, I don't think there is anything wrong with Harris' braking technique. It sounds correct to me. I would do a cool down lap and things should be fine.
However, I still think that disc warping can occur as well. I have heard plenty of people say that they have had their discs inspected and they have been found to be warped.
For what its worth, I don't think there is anything wrong with Harris' braking technique. It sounds correct to me. I would do a cool down lap and things should be fine.
Harris_I said:
I will be sure to do cooling down laps after each session without touching the brakes.
While cooling down laps are a good idea, I don't think you need to go quite that far - just be careful not to leave the disks and pads in contact for too long when very hot - especially when stationary. My description was for how to attempt to fix the "warped" (deposited) discs not for every session.
And I'm quite happy to belive that my discs were not in fact warped, as such, and just "deposited" as described above, but I guess that's just how non-meisters (like me) refer to them!
>> Edited by Joe911 on Tuesday 23 November 12:24
Apparently one of the aftermarket companies do a kit especially for this.
I myself have never been unfortunate to get any brake fade on mine or warped discs, so never seen need for getting this kit. The GT3 brakes IMHO are amazing.
The only problem i do get with them is if you don't do a cooling down lap or two. This causes cracks to form from the drilled holes in the disc, which are OK to start, but if they get too bad then they need to be replaced.
( i have done 3x trackdays on my latest set and they are cracked already !!, no loss of performance though)
G.
I myself have never been unfortunate to get any brake fade on mine or warped discs, so never seen need for getting this kit. The GT3 brakes IMHO are amazing.
The only problem i do get with them is if you don't do a cooling down lap or two. This causes cracks to form from the drilled holes in the disc, which are OK to start, but if they get too bad then they need to be replaced.
( i have done 3x trackdays on my latest set and they are cracked already !!, no loss of performance though)
G.
johnny senna said:
Can someone tell me why Porsche don't just use grooved discs with better brake cooling rather than having drilled discs that just crack?
Have had grooved discs on previous car, they were a nightmare, as when they got hot, they caused an unbearable amount of friction noise that resonated around the cabin, and was very off putting.
Grooves can tend to eat a lot more of the pad surface away aswell.
G.
>> Edited by Glenn McMenamin on Wednesday 24th November 15:03
On a slightly different note, I recently changed from pagid yellows to PFC pads on my car (GT3 mk2) for a track day at Oulton and was quite surprised at how much noisier they were. This wasn't just on squealing which i expected but whirring and a sort of grumbling under braking. Did others notice this when they swopped pads?
It is possible to modify your circuit driving styles to allow your GT3 and brakes to 'breath' a little. Instead of stamping on them at the very last possible moment, APPLY the brakes progressively, firmly and quickley and come off them in the same way.
One of the problems is that so many drivers have been brought up on ABS cars which doesn't encourage any sort of feel or appreciation of weight transfer etc. The car's pitching and squating in violent changes of attitude and weight transfer is of no help to quick laps.
If the brakes are given just a small chance not to record the very highest temperatures, they will live longer and warp less.
One of the problems is that so many drivers have been brought up on ABS cars which doesn't encourage any sort of feel or appreciation of weight transfer etc. The car's pitching and squating in violent changes of attitude and weight transfer is of no help to quick laps.
If the brakes are given just a small chance not to record the very highest temperatures, they will live longer and warp less.
Glenn McMenamin said:
Can someone tell me why Porsche don't just use grooved discs with better brake cooling rather than having drilled discs that just crack?
Have had grooved discs on previous car, they were a nightmare, as when they got hot, they caused an unbearable amount of friction noise that resonated around the cabin, and was very off putting.
Grooves can tend to eat a lot more of the pad surface away aswell.
G.
>> Edited by Glenn McMenamin on Wednesday 24th November 15:03
I see, Glen. But couldn't Porsche engineer out these problems? Perhaps fitting drilled discs is a scam to get us all buying more brake discs than we should really need to?
johnny senna said:
I see, Glen. But couldn't Porsche engineer out these problems? Perhaps fitting drilled discs is a scam to get us all buying more brake discs than we should really need to?
While I love a good conspiracy theory, I do not believe that Porsche fit naff equipment knowing that it'll be a good earner later. They have too much to lose to do this. Also, I think (for the car industry) they are 'honest' (come on, stop laughing) in terms of the cars they produce.
Porsche have always fitted proper brakes and suited to the performance of the car (unlike others - like TVR who used to be - with the Griff's for example - taking the piss - i.e. Ford Granada brakes - but then the car has to actually be running for the brakes to be of any use
Porsche fit brakes good enough for 99.5% of their customers, with BMW it's probably nearer 97%.
(I'm making those numbers up - but hopefully you see the point). If you want to run BMW's hard on track days you almost certainly want to upgrade the brakes - with a 911 you're less likely to need it.
I run standard calipers and disks - and just run better pads and fluid.
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