afinepoint

I intend to bleed and look at the brakes on my 84 Targa tomorrow but in the interim I am soliciting advice.

After several laps of hard braking the brakes suddenly fade. The only warning is sponginess and by the next turn they are gone. The pedal goes to the floor.

Here are some other facts.

1. The harder the braking the sooner they go. There wasn't a problem Saturday but today I was carrying greater speed and braking much harder.

2. After a lap at low speed or sitting for a couple of minutes the pedal is again firm. The brakes were fine all the way home from VIR. It is heat related.

3. The instructor doesn't think it is air in the lines because the problem goes away.

Ideas? I did a search but found nothing.

I need to solve this before I will allow the car back on the track.

The car has new pads and Super Blue racing fluid that is about 15-20K miles old. They were well bled. I am researching which pads are on the car.

Eventually I would like to upgrade the calipers and pads. Suggestions?

Reg

Steve Weiner-Rennsport Systems

Reg:

What you are experiencing is boiled brake fluid from overheating. This is due to absorbed moisture in the fluid that flashes into steam (compressible), not air in the lines. The pads, rotors, and calipers are getting too hot and cannot dissipate the heat being generated before the fluid fails.

You can minimize this by flushing fresh fluid before each event, but the Carrera is a heavy, powerful car that can be run clear out of brakes on a track.

The ultimate solution is installing a larger brake system that has much greater thermal dissipation capacity than what your currently have. We've had very good luck with either 930 Turbo brakes or the new Brembo GTP ones (depending on wheel sizes)

afinepoint

Thanks Steve,

I asked about this afterwards but I felt I was waived off. The boiling makes sense. So as the brakes cool the steam condenses and "poof" the problem is gone. I just never thought I could or would be able to push the brakes beyond their capability. I have heard so many times how good the OEM system is. I knew by day;s end I needed more in the way of brakes.

Steve, I don't have alot of money to to it over again any time soon so what is the best I can do now that will keep me out of trouble on the track but allow me to still send the kids to college? The 930's or the Brembos?

It was fun hanging with the 993's, 944 turbos and 996's today. If only in the turns.

Reg

Bill Gregory

Reg,

That's the first problem, as your fluid should have been bled before the event, to mitigate the condition Steve described.

Next, you want to get more cooling air to the rotors. A kit like those offered by Paragon Products or AJ USA with under a-arm scoops which route air to the eye of the rotor can be a significant help in keeping the rotors cooler, hence reducing the chance of boiling brake fluid. If you have Fuchs, be sure and get the additional plate to keep the air from exiting the hub. Smart Racing makes a nice set, and I'm sure the other vendors carry them as well.

When you pulled into the pits after each run, did you use your brakes to stop when you parked? Major contributor to reducing brake fluid life at the track, as you leave your brake pads parked against the still very hot rotor. As an alternative, as you are coasting to nearly to a stop, put the shift into 1st gear, depress the clutch, shut the engine off, and feather the clutch to stop.

Steve Weiner-Rennsport Systems

Reg:

The cheapest thing is just as Bill said; fresh fluid and a brake cooling kit. These things will help.

That said, if you are really using the brakes and driving the car close to its potential, then the only real solution is larger brakes.

930 brakes are the most expensive but fit inside any wheel you have. GTP-L Brembo's are significantly cheaper and fit inside 7" and 8"x 16" Fuchs but you'll need a pair of 944 Turbo Fuchs (7x16) for the front for caliper clearance.

Please contact me directly for pricing.

afinepoint

I never heard of this. Yes, I do use the brakes to stop the car. The only thing I have been instructed on is not using the parking brake after a run. I will try and remember your advice the next time.

I do have Fuchs on the car. I was thinking today of the modern exotics and even some cars from the 50's that ported air to the rotors and planned on asking around about such a fix. Bill, the add for the vented system on the Paragon sites states "For factory vented rotors only". Is that what the 84 911s have?

With bleeding the lines and an air kit can I still overwhelm the present brakes?

Which will give me the stopping power I need on the track; what setup will be beyond the car's and my abilities? Honestly I really don't want to feel any fading at all but I know that is impractical or impossibly expensive. For now I need to stay on line, at speed and more importantly on the track.

Thanks Steve for the second reply. You were posting while I was writing. I want stopping power. I will find the money. As far as I am concerned brakes are the most important system on any car. I will be in touch.

Reg

P.S. Any significance regarding rotor design for stopping ability? Drilled vs. slotted vs. cryogenic?

Steve Weiner-Rennsport Systems

Hi Reg:

'84 Carrera's do indeed have vented rotors.

Even with Castrol SRF fluid (THE very best) and a brake cooling kit, stock Carrera brakes can fail when being used hard on the track for consecutive laps. They are OK for street use.

The best setup thats beyond what you can do with the car, even with a 3.6 litre engine would be the Brembo GTP's. GTP brakes need 17" wheels but the GTP-L brakes will fit inside 16" (7x16 944 Turbo Fuchs) Fuchs wheels.

You are correct, good brakes are THE single most important aspect of any car.

jaydubya

Just want to add that every F class PCA racer (most if not all carreras I believe) must use stock rotors and calipers and generally speaking they are getting by fine. Steve's suggestion of bigger brakes is a great solution, but you CAN push your carrera/sc hard and use the stock rotors/calipers. Here's what I would do, in order, assuming that your rotors are within factory specs:

high quality brake fluid. Nothing wrong with ATE type 200 / super blue, I use it. However, there are better / more expensive options. Bleed all four corners before every event, flush at least once a season. My guess is that this will completely eliminate the problem (for a while until you start to put even more stress on your braking system).

race pads (this will not cool things off but will help you stop more effectively with easier modulation. It will also prevent brake fade - see below). I like Performance Friction Carbon Metallic (call them, they will help you select pads), but many people like Pagid too. Talk to the manufacturers about your intended use as there is no such thing as a pad that works optimally for both street and track.

cool brake kit - this makes a BIG difference. As was mentioned, these usually come with a block-off plate to force the air out the vents on the edge of the calipers.

Rotors - I have had problems with aftermarket slotted rotors, have never used drilled rotors. I suggest sticking with the stock Zimmerman rotors or if you can afford it lots of PCA racers use the frozen rotors (again starting with Zimmermans).

Finally - your brakes are not fading (which usually refers to a hard pedal but no ability to stop - related to pads). You are boiling the fluid.

DGaunt

I don;t know your skill level, but you mentioned having an instructor. When I first started DE, i frequently overdrove the brakes. However when I learned how to carry more speed in the corners, taking the excess load off the brakes, the brakes became completly adequate for waht the suspension and tires were capable of. As the heat generated is exponential, even moderate increases in entry speed takes a great deal of strain off the brakes.

Noel

Jay brought up a good point about pads. What was the condition of the pads you used? They should be new or like new? It is advisable to toss the pads when they are 50% for the track.

Make sure your brake system is 100% first to make sure you have a good baseline, then add cooling.

You didn't mention how much track experience you have but many starting out use their brakes too much. They tend to apply them in a similar manner as if they were driving on the street. That is soft braking to hard barking. On a track, you should start braking very hard then ease off. Doing this you will find that you tend to be off the brakes more, thus increasing the cooling. Also the brake temps tend to spike using this approach and the heat is more quickly dissipated before sinking into the calipers and thus boiling the fluid. Do a search on this subject here and on Pelican Parts and you will find that this topic is well covered.

BTW, my setup is fine for me now (See my sig) using Hawk Blue pads. However, if I switched back to race tires (Which I don’t find as fun), then I would have to call Steve and order the Brembo setup because stickier tires will only make matters worse.

Good luck.

afinepoint

Excellent advice guys,

I will start with the last questions first:

The pads are practically new. I think they are metal masters but I am still researching.

I have been to two other track events. Only one was at VIR.

I braked as and when the instructor wished. I must have heard him say "brake hard" about 50 times in the ear piece. Then "brake harder" the next time. So in actuallity I was not pushing the brakes as hard as he wanted. I let him know I had to drive home what I brought to the track so I did not intend to overstress the car. This brings up another point. I can't do much once at the track. I don't have a trailer. ( Anyone know of a good deal out there?)

Dave, I am not that skilled but towards the end of the day the instructor was completely satisfied with my speed in the turns. The Michelin Pilot Sports were "skidding" the way he wanted. I am somewhat horsepower limited. As Scotty would say "She's giving me all she's got". I do need to work on shifting but I can tell that I am only going to get modest increases in acceleration but, as you wrote that may be enough.

I don't want to be near the limits of the brakes. I want them to be beyond what I and a non-modified 84 Carrera can demand.

Jay, I hear you. I do plan to do a good bleed. I decided to wait til someone got home to help. I think I will order race pads and take them to the next event. Do a run with stock then swap out and see the difference. Just need to remember to take them out for the drive home.

I am listening to all the advice. What I am looking at is the $$$ investment as well. The lower cost of cooling kits vs. the benefits of bigger brakes.

But I do agree with all. I was boiling the fluid. 99% of the other cars - older, newer, faster and slower finished each run. Fresh fluid will solve much/most of the issue.

Still plan to give you a ring Steve.

Reg

Steve Weiner-Rennsport Systems

Hi Reg:

Please let me know what pads you have. Metalmasters are THE worst, IMHO.

Get yourself a Motive Brake Bleeder. Then, you can pressure bleed the brakes all by yourself. Never use the "pump the pedal" routine.

Indeed, fresh Super Blue or SRF fluid before each event, better pads, and a cooling kit will help at least for now.

afinepoint

Bleeding done. I did not do an entire flush just what I thought would refill the calipers. BTW how much should you flush from each brake. How much does a caliper hold?

I intend to do a change out before the next event. Looks like the rotors are up for a change out too. Front and rear thickness .25 inches. Min spec front is .43 and rear .33 per Haynes.

Again thanks.

Reg

Steve Weiner-Rennsport Systems

When I flush the brakes, I run a whole litre through the system beginning at the RR, LR, RF and finally LF caliper.

Sounds like you need new rotors but thankfully, those are cheap.

afinepoint

I did 1/2 liter for now. It was what was left in the can. Of course I did not use it to the bottom. Normally I don't use opened cans but I thought with Super Blue what was in the can was better than what was in the calipers. I will follow up with a liter of the gold.

I took the car out to insure no air in the lines. Heating the rotors to track temp will have to wait.

Steve I am trying to figure out the Brembo's. Are the GTP Lightweight kits for 1969-1989 Porsche 911s the same weight as the GTPs? I am looking at the Rennsport site. How is their- the lightweights stopping power compared to the Big Reds? Compared with the GTPs. Having to buy two wheels for the lightweights would tip the choice away from them. I like to do my homework well ahead of a purchase.

Reg