Not sure anyone has had an issue with break feel on the 987 or an experience with losing their breaks on track but I thought I would post.
I have been a long time track junkie and have had noticed over the last season or two that the brake pedal and feel on my 06 Cayman has gotten spongier with time. I change pads, discs, rotors and brake fluid religiously. Bleeding the brakes helped and driving around town had not really been an issue. Nonetheless, after a day or so at the track the brake pedal gets very spongy and while the car stops fine it has been, well, less than confidence inspiring. One other thing I noticed is that the ABS activates with hard braking. I had thought that this was normal and I was merely threshold breaking. During an event at Watkins I lost my brakes on the back straight at around 135-140 mph. When I say "lost my brakes" I mean the pedal went to the floor. I was able to pump the brakes and get the car to slow, downshift and somehow managed to stay on track. The car has been at my local Porsche race shop for about 4 week - they have an excellent reputation and I trust their work. They replaced the master cylinder (upgraded to GT3) and that did not correct the issue. Next, we sent the ABS unit out to be rebuilt. This seems to have corrected the problem.
Right now the breaks feel great, but I am a bit skeptical. They typically feel fine around town and the issue develops when I track the car. I am headed to Mid Ohio next weekend, so wish me luck. I will repost with updates.
Is it possible you got air in the ABS unit? Have you totally evacuated all the fluid from your reservoir & lines? That's a good way to get air into your ABS. If you get air in it, you have to have special tools to bleed the ABS - regular bleeding will not remove the air from the ABS.
You were fortunate to stay on the track. I watch videos of older tracks (like WG & Road Am) and see lots of Armco not far off the track. Those tracks look like fun, but there's not much margin for error. I'll stay on COTA & Indy where there's plenty of run off room.
I run Motol high temp brake fluid. It gets changed in the beginning of the season and the brakes are bled after each weekend. The brakes do get very hot - I was suspect that the calipers needed to be rebuild, I have GT 3 ducts up front and have considered upgrading to GT 2 ducks but am concerned I will destroy them on the street. I have seen more complex methods of getting air to the brakes but didn't want to go through the trouble. I may need to reconsider.
I’m also running Motul / gt3 ducts and have had similar experiences as you: I boiled the fluid going into turn 1 at Pittrace. I was reading about the Sahlen team that runs in IMSA and AER, and they have a titanium shim installed between the brake pads and caliper pistons to insulate the fluid better. I’m planning on getting a set since they seem to be effective. I’m not really that happy with Motul RBF600, it seems to absorb water way too quickly. I’m planning on switching to Castrol SRF in the spring.
WG is an awesome track. I was fortunate because after the chicane there is a broad high speed right hander. Gotta hate the ARMCO - not only what it does to the car but the WG folks charge you per foot when you mess it up
Keep as fresh of fluid as you can and use SRF in conjunction with track pads = success at the point at which you are with regards with what you have done!
I had used Castrol SRF in the past without issues. I am not sure if that could explain it or that I am driving the car better/harder and putting more heat into the brakes. I am consistently 2-3 seconds faster around Mid Ohio now then when I ran the Castrol. If the newly rebuild ABS doesn't correct the issue then I will change back to the Castrol. The weather looks good for Friday and Saturday so I will post an update.
Let me know how the shims work. Sounds like a simple solution.
So, the weekend started ok. But, after 1/2 day of hot laps the brakes progressively got softer and softer until the pedal went to the floor (or near enough). I could always get the car to stop/brake but it requires pumping the brakes once or twice to bring the pedal up. It seems the hotter the brakes the worse the pedal. I bled the brakes twice this weekend and got a firm pedal. There was no air in the line or any leaking fluid. Unfortunately, the brakes worked normally for a bit then progressively got softer. Ugh!
I am going to replace the brake lines to stainless steel and rebuild the calipers next. I cannot think of anything else that would cause this. While I have everything apart I am going to figure out how to get some air ducting to the front brakes. Better cooling can't hurt.
Stainless steel brake hoses won't solve your problem. Not sure rebuilding the calipers will either. Are you boiling your fluid? Are you monitoring rotor and pad / caliper temperatures, and if so what are you seeing?
I haven't checked the brake temps but clearly they generate a bunch of heat. My front calipers have turned from red to purple. I don't think I am boiling my fluid but not sure how I would know.
Absolutely no air when bleeding the brakes. I will work on brake cooling for sure but am skeptical. If overheating brakes is the cause, why aren't others experiencing this when tracking their cars? I know I am a rock star on the track but come on
You absolutely boiled your brake fluid. When I run the COTA track which is hard on brakes due to the long straights I do the following:
1) Start weekend with fresh high temp fluid (Motul 660)
2) Start weekend with fresh brake pads. Thicker pads absorb more heat.
3) I bleed the brakes at the end of each day to flush out the burned fluid replace with fresh.
4) Added better GT2 brake ducts under car and cut out larger holes in the wheel well vents.
5) You can upgrade your rotors to Giro Disc or other that are larger and better vented. I have used both Giro Disc and Big Brake kits either will help.
I just wanted to update you guys as I have seen a bunch of threads on this topic - failure of the brakes once they get too hot. This past weekend I took the calipers off and rebuild them. Quite easy to do actually. The Brembro calipers use aluminum pistons that are coated with a thin gray material. (I suspect this is to prevent corrosion from steel in direct contact with aluminum.) Interestingly, when I tore apart the front calipers, two or three of these pistons had pitting and chips in the gray surface material. This defect extended along the piston into the caliper past the internal seals. I suspect that these defects would allow air to enter the system without allowing fluid to leak out. I replaced the pistons with aftermarket stainless steel pistons and put new seals and dust covers.
I am running Nelson Ledges next week and will post an update. If this solves the problem I will post photos of the pistons - both normal and one with the defect in surface material.
I am running Nelson Ledges next week and will post an update. If this solves the problem I will post photos of the pistons - both normal and one with the defect in surface material.
So the rebuilding of the calipers worked. No fade even after all day of hot laps. I suspect this is the issue that others have been experiencing with brake fade, soft pedal or brake failure.
When I took the calipers apart this is what I found in the front. The normal pistons have a smooth gray coating but as you can see some of this coating was pitted and chipped off. I suspect this is where air was entering the system under extreme conditions like hot laps. I rebuild the calipers following videos on line - pretty straight forward but took me half the day nonetheless. The one thing that seemed easy but was a PITA was using compressed air to remove the calipers. One piston would come out but not the other 3. I ended up making shims so they would all come out nearly all the way without any one flying out prematurely.
I purchased rebuild kits from RB performance part #BP-422BS and BP-404SP with high temp (blue) dust seals. I used new stainless steel pistons on the front calipers (the pitted ones) and replaced all the dust rings and inner seals on all 4 calipers. Bled the system and now I have confidence inspiring brakes again! I would recommend everyone rebuild their calipers if they are experiencing these issues. The total cost was about $350.00 give or take. With each new caliper around $450-$500 each, this seemed like a no brainer.
To answer the few other questions outstanding - I run Nitto's NT01 and carbotech brake pads.