A bad day at the track

forty3

forty3

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After looking forward to a track day at castle combe for the last few months the experience has sadly been cut short.

After my first 15 minute session there was a loud noise coming from the front brakes which I put down to one of the heatshields coming loose.

After letting the car cool down I took it for a gentle drive through the car park and suffered a complete brake failure resulting in me having to use a hedge to stop.

The end result is a knackered charge cooler on top of the undiagnosed brake issue and a damaged front wing.

I've ordered a hx cooler from the States so now just need to sort any bits for fitting.

Anyone have any ideas on a cause for the brake failure? I've got rs4 calipers, braided lines, DS2500 pads and no loss of brake fluid?
 
A lot of people have mentioned there's a big lack of cooling on the brakes for these cars. But I would have thought you'd have noticed them cooking rather then them just stopping working.
If it is down to a lack of cooling the maccan under floor ducts are one option, a bit of trimming to get them to fit but people seem to rate them
 
As above there is poor cooling on the front brakes. I modded mine with TTRS front brake cooling ducts and Macan brake ducts. Have a look in my build thread. DS2500 pads are not that good really for a big heavy car even though it is running RS4 brakes. I would look for something a bit better. What ever the issue with the brakes you are fortunate that they didn't fail on the track, I suspect something has been chafing on a hose or a pipe and it's related to the noise you could hear. If the pedal is going to the floor you have a leak in the system somewhere.What brake fluid are you using and when was the last time it was changed.
 
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Brake fluid is only a couple of months old and was changed by a trusted garage.

No loss of fluid anywhere which is baffling.

Now that the car is cool I can get some pedal pressure back when pumping the pedal but haven't tried it with the engine running.

The discs were blue after the laps so the brakes definitely had a bit of a hard time.
 
Pad material come away from the backing ?
Had a similar issue on the track car at Donnington - fortunately happened at goddards, coasted down the straight and into the gravel :tearsofjoy:
 
I'm hoping that it was an issue with heat as I drove the car off the recovery truck and onto my drive last night without any issue.

After reading @desertstorm build thread I'm going to have a good go at sorting some airflow to the front brakes and have ordered macan ducts and also put in a parts request for some TTRS wheel liners with vents in them. I also intend on drilling out the front fog covers to let air get to the wheel vents once they're installed.

Also not convinced that the brake fluid didn't overheat so have ordered some Motul RBF 660 to do a complete fluid change.

Hopefully one or all of these things will sort the issue.
 
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Certainly sounds like something more than just brake fade if you experienced a loud noise, maybe as Jetty said you've lost a lining off one of the pads with it getting so hot
 
I've had the front brakes off and sent away for a refurb as one of the pistons felt a bit stiff but the pads themselves looked OK although more worn than I would have expected for the mileage I've done on them.

I have found a broken brake disc heatshield bolt so think that the loose shield is the noise I was hearing.

The more I think about it the more I'm convinced that it was the brake fluid. Pedal feel was OK on the track but the problem happened after I stopped the car for a bit and therefore stopped any cooling for the brakes.

Hopefully some cooling mods along with uprated fluid will stop this happening again.
 
Did you do a decent cool down lap before you came into the pits?. If the brake discs were still pretty toasty when you parked the car the heat soak from the discs could have boiled the fluid in the caliper. They are big lumps of iron and hold a lot of heat. I would ditch the back plates on the front discs, I cut mine down to a small piece that just protects the ABS sensor from direct radiated heat.
Motul 600 or 660 is probably the best performance/ pound brake fluid.
 
The brake fluid is whatever was put in by the mechanic when it was replaced about 6 months ago. Really didn't think about boiling it so didn't request anything special.

The brakes were still smoking when I parked up so definitely would have continued to heat the fluid. Using the last lap as a cool down lap is also another lesson learned.

I cut the heatshields right down yesterday much the same as @desertstorm has and also took delivery of 1.5l of Motul 660 this afternoon. The braking system is getting a major overhaul whilst I wait for the Merc racing cooler to arrive from the states - 8 pots are off the car and being rebuilt, new discs and pads for the rears, cooling mods plus a fluid change.
 
That will be your problem then. If you were using standard dot 4 fluid it would have exceeded it's operating range, even the Motul would probably have had similar issues if you didn't cool the brakes. It's not only the brakes it's turbo , coolant and oil temps as well that need some time to get down to a reasonable temperature.
 
audi upgrades
You'll have boiled the fluid get it swapped out for dot 5.1.
 
The Motul has higher dry and wet boiling points than DOT 5.1 hence why I opted for it.

Calipers are due back from rebuild tomorrow and the cooler has arrived at Heathrow so hopefully get hold of that this week.

My poor car is looking a bit sorry for itself right now

XkyCMC.jpg


n4vFI0.jpg
 
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I have spotted a battery charger sitting on your car, and it looks very like the one I bought a few years ago - and it is not considered suitable for use with an AGM battery, so maybe watch out what you are doing to that battery? I'll only ever use a CTEK charger on my AGM and other Start/Stop batteries. The "RAC" 8Amp charger is now only used for old style batteries.
 
GarethS4 said:
What are you doing with it ??
Click to expand...

Fitting a new supercharger heat exchanger, TTRS wheel arch vents, front caliper rebuild and sent a few bits off to the paint shop for repair or colour coding.

Exchanger and rebuilt calipers are now fitted but still need to do a proper bleed on both systems. Wheel vents are also fitted. Bits are due back from the paint shop on Weednesday so hoping to have it all back together by the weekend.
 
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Do you have a link/part numbers/pictures of the TTRS wheel arch vents?
 
Finally put back together and on the road

N9djZu.jpg


I contacted Castle Combe to explain what happened on the off chance they might offer me some sort of discount on another track day. Amazingly they have given me a place on another day in September free of charge. Really happy with that!

Less positive has been my experience with Morris track day insurance and the recovery company they use brittania rescue but I'll save my rant on that whole pantomime for the insurance section.
 
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I picked up my Macan brake ducts at the local Porsche dealer in Sutton Coldfield. Rang up the parts dept and paid on my Credit Card. Then popped over when they came in.Had a look at some of the nice cars there while I was there.
Castle Combe is a hard circuit on brakes, I only managed about 5 laps before I picked up quite a vibration on the brakes, That was because I only had red stuff pads on, the brakes never actually failed though.This was also before I fitted the brake cooling upgrades and changed the front calipers for 4 pot Brembos. I would expect to be able to get a lot more laps in with the current set up on the car.
 
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Finally finished all the repairs and modifications. Last job was to change the brake fluid for motul RBF660.

Can't wait until September now to give Castle Combe another go.

Hopefully I won't be coming back on a low loader next time!
 
Boiled the fluid.

Get some RBF660 in there. Not the cheapest stuff garages get hold of.
 
A quick update on this....

Yesterday I went back to Castle Combe and gave the S4 a proper thrashing with no issues.

There's no getting away from the fact that the car is heavy and can be outcornered by most things lighter than it but the amount of grip and straight line speed of the S4 is incredible.

It's clear that brake cooling mods are essential if a car this heavy is to be driven hard.
 
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