trackday brakes for C4?

[martin964]

Havig recently done an airfield trackday in my C4 (and loving it!), I was wondering what setup in terms of disks and pads are used by fellow 964 trackdayers??

My brakes were fine before, but the front discs (and probably the backs) are now very warped!

The front disks/pads were new in july last year by autofarm so only had about 7k miles on them.

on the day:-

I did do a warmdown lap at the end of each session, where I hardly used the brakes.
I did leave the car in gear with the handbrake off in the paddock
The brake pedal did not go soft at any point (and the stop at the end of the runway was 110-30 each lap)
I did about 7 sessions through the day with 15-20mins being the shortest period in the paddock (no session was longer than 25mins).
I did get squeal from the brakes on the last laps in the morning and whilst leaveing the circuit for lunch, but this was gone in the afternoon.
the fluid did get hot enough to come out of the overflow in the drivers sill on the day and that evening , but looks like it was slightly overfull(and it was only a small patch like a 10p each time in the paddock) and stopped the next day.

The car is currently getting the discs refaced at Northway, but I want to possibly do another trackday (or maybe lots more...) without buying new discs each time!

Is there anything in the above that I have done which would warp the discs no matter what? or do I just need better discs/pads/cooling for trckdays?

any advice gratefully recieved!

martin

 

[Steve Brookes]

How do you know the discs are warped? What are the symptoms? Many people come to the conclusion that they have warped the discs when they feel judder from the brakes. I have it on good authority that it is quite rare to warp the discs. A disc that feels warped is often actually the symptom of uneven pad deposition on the discs.

 

[tim_haskins]

I have big reds on the front and 993 rear calipers. The extra disc size and extra pad size on the front help to keep the brakes cooler. Problem is that they are ££££. Really pleased with mine although they are probably a bit overkill if I am honest. Have you tried different pads? I always felt the 964 brakes were good but I upgraded mainly due to the fact I wanted the look. (sad but true!)

tim

 

[martin964]

ORIGINAL: Steve Brookes

How do you know the discs are warped? What are the symptoms? Many people come to the conclusion that they have warped the discs when they feel judder from the brakes. I have it on good authority that it is quite rare to warp the discs. A disc that feels warped is often actually the symptom of uneven pad deposition on the discs.

Steve,
a fair point! I had forgotten about pad deposition and just assumed discs. I guess that refacing the discs ultimately either removes the pad material or trues up the discs, so either way I am ok (for now). Are there any particular signs of pad material unevenly deposited on the discs? if so then it is something I can look for next time no matter what discs/pads are on the car.

Ray has told me that the rears are fine, so thats also good news.

Tim,
I guess the big reds do the job, but as you say are £££. I want to keep the car near standard if poss, so I may look into diferent pads if there are any good recommendations.

cheers

martin

 

[Steve Brookes]

Martin, I think this subject of brakes and trackday stress is fascinating and well worth discussing once in a while. Like yourself I've experienced juddering brakes more than once on track and been through the process of solving the problem. Here's an article on the 'warped brake disc myth' that is well worth a read:

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

I agree with Tim on both counts: a] bigger brakes are the best way to get better cooling (and look ace!) and b] normal brakes are more than up to the task if looked after properly (the 964s in the club championship HAVE to use normal brakes and they work extremely well).

I've got normal brakes with OEM discs made by Sebro. The current discs are solid (i.e. not drilled) and have done at least a dozen track days. I use slightly higher boiling point brake fluid (castrol response super dot 4) and have braided hoses. I flush the fluid (1 litre does it) after every 3 trackdays and put Pagid RS15 grey pads in the day before and carry out the bedding procedure in the above article (I put the textar road pads back in between trackdays and again bed them in). With this set up, touch wood, I don't get judder.

I used to get a bit of judder early on in a trackday which then disappeared as the day wore on. I'm 99% certain this was because I hadn't bedded the pads correctly before the day and therefore it took a couple of sessions for them come right. If in your case you didn't get judder until later on, my bet would be that your pads were overheating and starting to crumble and put uneven deposits on the disc faces. So things I would try if I were you would be:

1. Change the fluid regularly
2. Use higher temp brake pads
3. Ensure you do proper cool down laps (a couple trying not to use the brakes)
4. Change the brake hoses if there is no record of them recently being changed (original Porsche rubber ones or Goodrich braided)
5. Regularly check that your wheel nuts are torqued correctly (130 nm).

p.s. by having a C4 you're one step ahead of me because of the 4 pot rear calipers - I used have the small 2 pots on the rear of my C2 which overheated very quickly. Having my pedal go to the floor when trying to brake for the melbourne hairpin at Donington used to really focus my senses! []

 

[Steve Brookes]

pps. If you fancy a proper trackday I'm going to Rockingham on Saturday 14th of August with a bunch of Porsche mates.We've got a group booking rate if you're interested []

 

[martin964]

ORIGINAL: Steve Brookes

Martin, I think this subject of brakes and trackday stress is fascinating and well worth discussing once in a while. Like yourself I've experienced juddering brakes more than once on track and been through the process of solving the problem. Here's an article on the 'warped brake disc myth' that is well worth a read:

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

I agree with Tim on both counts: a] bigger brakes are the best way to get better cooling (and look ace!) and b] normal brakes are more than up to the task if looked after properly (the 964s in the club championship HAVE to use normal brakes and they work extremely well).

I've got normal brakes with OEM discs made by Sebro. The current discs are solid (i.e. not drilled) and have done at least a dozen track days. I use slightly higher boiling point brake fluid (castrol response super dot 4) and have braided hoses. I flush the fluid (1 litre does it) after every 3 trackdays and put Pagid RS15 grey pads in the day before and carry out the bedding procedure in the above article (I put the textar road pads back in between trackdays and again bed them in). With this set up, touch wood, I don't get judder.

I used to get a bit of judder early on in a trackday which then disappeared as the day wore on. I'm 99% certain this was because I hadn't bedded the pads correctly before the day and therefore it took a couple of sessions for them come right. If in your case you didn't get judder until later on, my bet would be that your pads were overheating and starting to crumble and put uneven deposits on the disc faces. So things I would try if I were you would be:

1. Change the fluid regularly
2. Use higher temp brake pads
3. Ensure you do proper cool down laps (a couple trying not to use the brakes)
4. Change the brake hoses if there is no record of them recently being changed (original Porsche rubber ones or Goodrich braided)
5. Regularly check that your wheel nuts are torqued correctly (130 nm).

p.s. by having a C4 you're one step ahead of me because of the 4 pot rear calipers - I used have the small 2 pots on the rear of my C2 which overheated very quickly. Having my pedal go to the floor when trying to brake for the melbourne hairpin at Donington used to really focus my senses! []

Steve,
thanks for the info. its good to know that I shouldn't have to spend loads of cash to get something that works on track!

I had forgotten to include that I already have braided hoses thanks to the PO, so one up there[]

I do need to do something different tthough, as Ray reckons the discs were definately warped as they were too bad to be just pad material on the discs[]

as you say I have the bigger rear calipers too, and the backs were fine, so maybe I need more cooling down laps/track pads/drilled disks(at worst) and I should be ok.

I wil have a read of that article when I get chance too, and will have a think and let you know about rockingham. When do you need to know by and how much? (pm/email me if that is easier)

martin

 

[Steve Brookes]

Hi Martin,

If Ray says they are warped I'm not going to argue they're not. With this in mind here's few more tips I've picked up from racing drivers, instructors and experienced trackdayers:

1. Personally I'm never on track for longer than 15 to 20 minutes. You mentioned doing stints of up to 25 minutes. That last 5 minutes could be the critical time when the brakes overheat. The Club championship racers are out for 30 minutes but they have cooling ducted to the discs which helps them.

2. On stopping in the paddock, leave the hand brake off and roll the car a few feet backwards and forwards while the brakes are cooling. This stops the pads sitting on just one part of the disc.

3. Racing drivers use the brakes less than us so there is more time for them to cool between braking zones. They say that us amateurs brake too soon and too softly. We go on the brakes gently and build the pressure where as they go hard on the pedal and smoothly release the pedal (especially when trail braking). The best way to learn 'their way' is to not to go as fast as you can on the straights which will give you confidence to brake later and harder .e.g. on a straight that you are reaching 100 mph, stop accelerating when you get to 90 mph and concentrate on your braking point - you'll soon get the confidence that you can lean on them hard and stop the early 'comfort braking' which is contributing to heating them up.

 

[tim_haskins]

Might also be worth fitting the rs cooling ducts to assist. Steve is bang on the money though to help with what you have.

The problem with drilled discs is that they can crack between the holes resulting in the need to replace them. I have 965 drilled discs on mine but I don't track my car so they are not a problem otherwise I would of used the standard solid discs. The bigger the brakes the better the cooling. I use the red stuff pads in mine and so far they seem ok but I could not comment on what they are like on a track. I wonder also if removing the back plates would help slightly with cooling (creating more airflow around the disc.

Were your disc genuine Porsche or aftermarket? This may also be a factor in disc quality. A few people in the past have had issues with some manufactures discs. I have heard good things about sebro discs but I personally prefer the genuine ones.I think sebro are also the choice of a few others on here.

Tim

 

[martin964]

guys - Thanks for your help and advice. I got the car back tonight and interestingly the outer edges of both discs appear to be missing the pad as they are not shiny from the trip home. I reckon the outer edges must have been the cluprits.

I definately need track pads and to do shorter sessions. I just got carried away and could have spent all day out there to be honest! [8|]

I also need to think about doing what steve has suggested and move the car around as the brakes cool in the paddock.

cheers

martin

 

[madmoog]

Drilled discs do crack, but until they get quite long (Porsche quote 7mm I think) or get to the edge of the disc that is considered normal "wear" and is fine. See link here http://www.porscheclubgbforum.com/tm.asp?m=119175

I've got big reds and since changing from standard pads to Pagid Yellows (Can't recall if RS19 or RS29 - not much difference - but essentially out and out endurance race pads) never had any problems - even from cold. What's been said about fluid, cooling down, hand brake and most important, once stopped immediately release the brakes - otherwise you'll be over heating pads, fluids quickly - not to mention the issue of cooking the small section of disc between the pads.

I do have cracks but not too bad and the car's main use is on the track, must just remember to clean out the4 holes between each trackday, as holes full of dust don't do much cooling []

Presuming that your fluid is good (and with a sufficiently high boiling point), and everything else is good, I'd suggest an upgrade of pads. Pagid do everything from fast road to full race and are very well respected - and with modern compounds work from cold and on the road (though depending on compound may squeal a bit - quite acceptable to me anyway). Alyn at AS Performance is good for advice on compounds and usage, and I've always found to offer the best prices.

Good luck, good brakes can really inspire confidence.

 

[martin964]

Thanks madmoog. I will definately be looking into different pads, and preferably ones I can use on the road so I don't have to keep swopping if at all possible.

cheers

Martin

 

[Steve Brookes]

ORIGINAL: martin964

Thanks madmoog. I will definately be looking into different pads, and preferably ones I can use on the road so I don't have to keep swopping if at all possible.

cheers

Martin

If you want something for the road and track then Pagid Blue (RS4-2) are probably the best option:

http://www.pagid-brake-pads.co.uk/products/rs42-blue-carbon-based.php

They have good initial bite from cold which is important when using them on the road, but be prepared for the price......about £200 per axle.

Pagid also do a 'sport' pad which is also blue (but darker in colour). These are cheaper and a little bit better than standard pads. I used them for a couple of trackdays with no issues except that I wore them out []. So they're not truly a trackday pad. I then moved onto the greys (about £230 per axle) and the increase in stopping power was startling. Because of the extra stopping power I spend less time on the brakes which brings me back to the point I made about less braking = more cooling time.

 

[RLambert]

As Steve says, for sensible track work the standard brakes are fine but make sure you have OEM discs, decent pads, any of the Pagid ones will do and a good quality brake fluid.

My race car weighs in at about 1300kg has standard solid discs, Pagid Yellows, RS29 and AP racing fluid and they work very well up to a point. Last year we were doing 30 minute races and we had a couple of very hot days and I did overheat the brakes which runined the front discs (very glazed with surface cracks) although I didn't suffer from any fade and they were usable for the full race distance. I don't have any cooling on them, other than the RS scoops which only let air through the bumper but I think I will fit some pipework to channel some air to the discs.

The RS' don't have any cooling either by the way so I'm sure you won't need any on your car.

 

[martin964]

Guys,
just wrote a long ish reply and the system crashed! AAARGH! suffice to say thanks for the help and its great to know that a full race machine uses standard discs!

I did look at pagid blue and sat down at the price, but if I do swop before trackdays then I guess they last longer...

cheers

martin

 

[Ben Savill]

Richard,

Can you describe the bedding procedure you go through when you have new discs / pads fitted? Also, do you have a procedure for warming up the brakes before really standing on them?

After some hard sessions at Spa, the front left disc is causing some very severe vibration under braking. I'm sure this is likely where I've overheated the pads and not bedded them in correctly so I would be interested to hear your thoughts.

Thanks,

Ben.