Brake issue

I originally posted in the UK section where I found the discussion on a searcQuote: Originally Posted by dans I also experiened what I presumed was brake fade at a recent trackday. Foot flat to the floory and nothing. Took 2 or 3 pumps to get a result. Pulled in on that lap, gave it a rest, went back out and everything was fine. I was probably out for about 20 minutes with some reasonably heavy braking. Very odd. My post: I just had the same experience on my sixth track day with this car. I flushed the brake system but on the second track day after that, the problem reoccured. Does anyone have any insights? It isn't a cooked brake fluid issue. h. Has anyone else encountered this?

Yes, many of us have experienced that. I haven't had the pedal go all the way to the floor, but it gets lower and lower ("soft pedal"), with reduced slowing effectiveness. A brief rest will usually bring braking effectiveness back, at least until the brakes get overheated again, maybe in about 10 minutes on track. Under heavy use, the whole brake system gets very hot. The heat is just too much for some brake fluid, so it boils and we experience "brake fade." A brake fluid with high dry and wet boiling points helps to prevent brake fade. I don't get brake fade with ATE brake fluid, but Castrol SRF has even higher boiling points (at a higher price).

because some people did not experience brake fade even when I went on a 50km stint on the track with 1G braking almost every corner, perhaps this is not a design issue. There is an issue with ABS brake system bleeding - the channels in the ABS system are not normally accessible for bleeding. See: StopTech : Balanced Brake Upgrades Porsche has a ABS cycle tool at the dealer which cycles the ABS during brake bleeding so that the bubbles trapped in the ABS channels will be released too. I suggest to go to do a brake bleed with the ABS tool at the nearest Porsche dealer then try again.

I would get a progressively softer pedal each session out on heavy braking tracks with few cool down opportunties. High friction pads helped a bit, I like Pagids. Stainless lines took out a bit more pedal play. I changed from Ate to Motul 600 and then Motul 660, no noticeable difference. Eventually I changed out the fronts to Brembo monoblock calipers and 2 piece rotors and am quite satisfied with them, currently using PFC01 pad.

The linked article is from 2001 and is not applicable to current Porsche ABS systems. Porsche's ABS system no longer needs to be cycled for a brake fluid bleed or flush. Try track pads (I've had great success w/Pagid yellows) and ATE 200/Super Racing Blue or better fluid. You're obviously overheating the pads and/or fluid you've been using.

How many track events are you guys doing between flushing the brake fluid? On the vette it was always done after each event. With a power bleeder its a one man job but is still messy. I dont know if they make an attachment for the porsche reservoir cover or not. Fluid color is not a good indication of boiling point. But dark fluid is not good... granted. I just cant wait for the '10 and my new car.

Would anyone with PCCB's chime in on this? I am getting ready to change my fluid with ATE blue and have heard this is excellent track fluid.

Brake fluid... Jim, you're running ATE Super Blue? I've got that in my 'Vette, and I'm very happy with it, but I wasn't quite sure if it was fully compatible with Porsche's sophisticated ABS. (It fixed the inconsistent braking in my Chevy) Consolidated, what sort of lines are you running? I've got Goodridge on my other car, but I was hoping to get something a bit more high quality for my Porsche. Finally, any sinking of the pedal sounds to me like boiled fluid. Usually glazed brakes still feel firm, they just don't do anything.

Alex: ATE works fine in Porsches. In fact, Michael G at Porsche of Roanoke said that's what they install.

This may be due to knockback as well: StopTech : Pad Knockback

Goodridge on all 4, Brembo ships their brake kits with Goodridge. I've been using their lines with steel fittings on road and racebikes for a long time w/o issue. I have seen lines with alloy fitting fail in person, due to tension and fatigue an elbow on a banjo bolt broke clean off.

Alright then. Sounds like time to place an order at Tire Rack.

I would go with Castrol SRF. A bit more money, but I imagine that is not an issue if you have PCCBs!

If that were the sole causative factor, wouldn't I have experienced this issue in my first or second track days(using stock pads). I have been using PAGID blues for my last 4 days,which I will not do again, as they have no bite. If knock back is the issue, then it is a design flaw. I've never experienced it with the RX-8, BMW 335, or C5 vette that I've tracked over the last few years.

Jimmyd: As I recall (it was over 20 years ago), I didn't experience brake fade with OEM brake fluid and pads until I went from the Green run group to Blue, where it suddenly became obvious that I needed more track worthy fluid, pads, and tires. I got all three at the same time, and it made a big difference in both my speed and my enjoyment. At the time I resented the more experienced trackers who had been advising me to just run the OEM stuff until it became obvious that it was holding me back. This is the first time I've heard the term "knock-back", but I've been told that hitting the curbing in corners can sometimes move the pads out of positon slightly, giving a very soft pedal at the next brake application. At that application the pads settle back into their proper position and provide normal pedal and slowing for the next application. I don't think I've ever experienced this, however.

Jim Thanks for the interesting thought. I take a fairly aggressive line over the curbing in a chicane, and this might be the cause. However, I've had no similar problems in other cars driving the same line; on the contrary, the Cayman is the only car that has given me any braking problems whether or not I was using stock fluid or pads. Whether it is a design problem, or something wrong with just my car, I doubt that I will never feel comfortable on the track again with it.