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Discussion Starter #1
Hello all. Just came back from a good/bad day at Hallet raceway. My 2012 cayman R has had a 4.2 liter Raby motor build. Just got a GMG roll bar-Recaro Halo Seat and 6 point harness installed. Fresh Motul 600 brake flush and Pagid yellows. First session on track went well-it was raining overnight and the track was wet in spots so I ran with PSM on kept the street/rain tires (PSS). On lap 10 the pedal went to the floor-boiled the fluid. Next session out I kept the PSM off as it was kicking in too often to maintain traction. Going much faster now but lost brakes on lap 5. Clearly this car makes a ton more power than stock-could reel in the GT3’s and GT4’s on the straights, so the brakes need to do a lot more work. I probably should have done a brake flush after the fluid boiled the first time. Looking at maximizing brake cooling for future events. I am thinking about Girodiscs, 997 turbo rear scoops and GT3 front scoops. Not sure that a bigger rotor/caliper is going to fix a heat dissipation issue (ie Essex system). Oh and I broke my right rear axel on hard acceleration. That is a story for another day.
 

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Thanks for the field report...

I see you had fresh Motul 600 before the track day started; I assume fairly recently before the track day. I have the GT-3 scoops on the front of my Cayman R, and finally replaced the stock front rotors with slotted Girodiscs a year or so ago when I started to get some hairline cracks between the holes in the factory rotors. I also run Motul 600 for most driving, or will put in Castrol SRF if I know I’ll be doing extended track work. Also have braided steel brake lines, but that’s more for brake feel and doesn’t impact heat dissipation or absorption at all as far as I know.

Haven’t had any real brake fade issues with this setup even after extended track sessions, admittedly with a lot less HP/speed than your car, and on a track I’m very familiar with so I don’t ride the brakes unnecessarily. I’ll typically pull in when my tires get too squirrely or when I see the coolant creeping up too far long before I note any loss of braking capability.

Tagged for interest; will be interesting to hear what solutions you come up with...
 

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Boiled fluid while only running PSS tires suggests there may still be some air bubbles in the calipers. I would carefully bleed all 4 corners, add 991 GT3 ducts, and make very sure that my tire diameters are within stock stagger (1"). Running a different stagger in diameter in a 987.2 will make PSM manic even while turned off and cause rapid brake overheat. I have seen this on tight tracks but once the 1" diameter stagger was restored, my brakes never overheated again.

My perception is that the 987.2 PSM is the 2nd generation and allows us far less slip angle than the later 981 cars. If I notice it kicking in I adjust my racing line and reduce slip angle on corner entry. Fritz the PSM wizard likes a nice straight braking zone and tends to interfere with excessive trail braking. Hyperactive PSM makes for hot brakes.
 

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Discussion Starter #4
Thanks, those are good thoughts. For session 2 I switched to NT1's in sized 245/40/18 front and 275/40/18 rear which are 25.55 inches diameter front and 26.65 inches back-this is .35 inches larger stager. I know others have used these sizes without problems but it might be triggering the PSM as I have never had brakes heat up so fast and fail so quickly. Either that or there was an air bubble in the system. I have driven the same track multiple times in my E36 M3 track car with similar lap times and never ever got close to even getting the brakes hot. I did not have a pyrometer with me but I could not get near the brakes, even the wheels were quite hot as they had soaked up heat from the brakes.



Boiled fluid while only running PSS tires suggests there may still be some air bubbles in the calipers. I would carefully bleed all 4 corners, add 991 GT3 ducts, and make very sure that my tire diameters are within stock stagger (1"). Running a different stagger in diameter in a 987.2 will make PSM manic even while turned off and cause rapid brake overheat. I have seen this on tight tracks but once the 1" diameter stagger was restored, my brakes never overheated again.

My perception is that the 987.2 PSM is the 2nd generation and allows us far less slip angle than the later 981 cars. If I notice it kicking in I adjust my racing line and reduce slip angle on corner entry. Fritz the PSM wizard likes a nice straight braking zone and tends to interfere with excessive trail braking. Hyperactive PSM makes for hot brakes.
 

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Before spending money - gather data. Next opportunity you get use a laser thermometer to map the temperatures of the brake rotors, calipers, wheels, master cylinder, etc as soon as you pull off the track.
 

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I have been having this problem for the past year or so with my 06 Cayman. In a stepwise fashion, I have replaced the master cylinder (upgraded to GT3), rebuild the ABS system, replaced brake fluid 2x with Motul, then SRF, upgraded to stainless brake lines and changed to higher temp pads as well as going from GT3 to GT2 brake ducts. Still experiencing the problem. Despite having a great pedal all day around town, once (on the track) I generate enough heat in the brakes, the pedal begins to get soft then goes to the floor. No leaking fluid. I can pump the brakes to get them to work, but at 135 mph this is alarming. The last event (Watkins Glen last weekend) I was able to bleed the brakes between runs and eliminate the pedal going all the way to the floor - at least for 20 min hot laps. I am rebuilding the calipers next week and will post if this works. I have spoken to a bunch of folks - from Porsche techs to other track junkies for insight. I know the brakes are #[email protected]$ HOT when I come off the track - my front calipers have turned from red to purple. The dust seals are shot. I suspect that the inner rubber ring may have a small defect or has gotten stiff from the heat cycling. Alternatively there may be a hair line crack in one of the pistons which may allow air in when heat causes the metal to expand. Taking them apart will hopefully reveal the issue.
 

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Discussion Starter #8
The more I research the issue the more I think this is a PSM issue. I didn’t think to to use the sport mode button since it doesn’t do anything for my new motor but will still up the threshold of PSM engagement since I have the sport chrono package. That with the PSM turned off is the least intrusive set up. I also exceeded stock trie stagger by 0.35 inches. I think my over heat destroyed my CV joint boot as well. Adding a motor making 450 hp/350 ftlbs torque make fora very upset PSM
 

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There's definitely a relationship between horsepower (or more correctly speed) and brake needs. The faster you move the mass of the car the more momentum you need to turn into heat through use of the brakes. That's all they really do... Finding out where the most heat is and dissipating it gains brake life before heat fade. The pedal going to the floor tells me - it's overheating the fluid. If you had a firm pedal but no brakes - that's pad/rotor combo.

Larger brake packages might be the next step - larger diameter rotors and more pistons in the calipers. Making sure the master cylinder and ABS module can move enough fluid to them as well.

Additionally - if you haven't done it already take a few advanced driving schools. It's all connected - I've had my butt handed to me by better drivers in inferior cars... Watch Sebina Schmidt make it around the Nuremberg ring in about 10 minutes in a Sprinter van on youtube. I doubt I could do that time in my Cayman S or on my motorcycle!
 

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Discussion Starter #10
For sure! I think the maximal scoops and girodiscs will help. Ultimately there is a lot of speed to bleed off at the end of turns and that creates a lot of heat.



There's definitely a relationship between horsepower (or more correctly speed) and brake needs. The faster you move the mass of the car the more momentum you need to turn into heat through use of the brakes. That's all they really do... Finding out where the most heat is and dissipating it gains brake life before heat fade. The pedal going to the floor tells me - it's overheating the fluid. If you had a firm pedal but no brakes - that's pad/rotor combo.

Larger brake packages might be the next step - larger diameter rotors and more pistons in the calipers. Making sure the master cylinder and ABS module can move enough fluid to them as well.

Additionally - if you haven't done it already take a few advanced driving schools. It's all connected - I've had my butt handed to me by better drivers in inferior cars... Watch Sebina Schmidt make it around the Nuremberg ring in about 10 minutes in a Sprinter van on youtube. I doubt I could do that time in my Cayman S or on my motorcycle!
 

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saildoc, JoshuaJ has a LS3 powered 987.1 Cayman that makes in excess of 500 hp at the wheels. He also owns a speed shop and has modified his braking system to meet the engine's/car speed needs. So, now this is a copy of a discussion in the 981 section is about how he was able to fit a 380 mm disk in front with 18 in Apex wheels. You can look up his shop in the vendor section of P9. He also has modified the front of his air intake to allow better air flow to the front brake area. I believe he has removed is air conditioner condenser to allow more air flow. You can look at his threads in the past to see how he installed, after the side radiators, the BGB ducting to direct the air flow to the front brakes. So JoshuaJ has you covered, give him an email from the attached link.III
11-19-2018, 08:57 AM
#5

joshuaj
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We use Brembo kits and they offer basically two options. I was running the Brembo GT kit with 355mm type 3 rotors along with Sebro slotted rear, GT3 master an Pagid Yellows. Setup worked great, zero issues on/off the track. Recently switched to a Brembo GT-S 380mm front and 345mm rear with typ3 3 rotors and RE10 pads. I only have one track day on the new setup but I REALLY like the RE10 pads! Just as good as yellows with less squeal on the street and supposedly better longevity (we'll see..).

The full front/rear kit is obviously a lot more expensive than a front GT3 Caliper swap, however a GT 355mm kit is a cost competitive solution that fits any 18" wheel with plenty of pad options and a better rotor then most GT3 kits offer. I need to get the 355mm kits added to our site, only the 380mm kits are up now: https://www.arcflashllc.com/collections/porsche-brakes

The GT-S kits are more track oriented and eliminate the dust seals, yet still retain approval for street applications due to the dual o-rings on the stainless pistons. They also have a high temp black anodized finish for better durability. The GT kits offer a more OEM look and hold up great on the track as well.

I do a agree with proper ducting, pads and fluid (this goes for big brakes too) that stock brakes can work. My only issue there is I want to spend my time at the track driving, not bleeding brakes in the pits in between sessions. The bigger brakes will get better pad/rotor life and longer bleeding intervals.

or from Rennlist BGB R track day build

BRAKES:
BGB Motorsports/Pro-Systems 997 GT3 6 Piston Front Brake Kit (380mm 2pc Front Disc)
OEM 997.2 GT3 Brake Master Cylinder
Brembo/Race Technologies Brake Pads - RE10 Front / DV11 Rear
OEM 996 GT2 Front Brake Ducts
Goodridge 4pc Braided Stainless Steel Brake Line Kit
Tarett Caliper Stud Kit
Castrol SRF Brake Fluid

 

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Most of the fluid related issues people are reporting are due to the caliper pistons being made from aluminum. Since the pistons are a great thermal conductor, the brake fluid sees way more heat than in a system with a phenolic or stainless piston. Adding a thermal break like a stainless or titanium shim is probably enough to fix it - at least, in my case it has been.
 

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I can’t tell from your post but if you are still running the stock calipers they are not up to the task at your HP/Speed level. Not upgrading your caliper/rotor you will never be happy. With more speed comes the need for more brakes. :)

Peter
 

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Discussion Starter #14
I do have the stock calipers on the car. I do feel the stopping power is a little weak. It is basically performing at the level of a 997.2 GT3 with the current power levels and that car has much bigger brakes. My race shop thinks bigger discs will fix the problem. I have found several upgrade options that work with my 18 inch APEX wheels. I could do the 997 GT3 caliper upgrade with 350mm discs in front, not sure about the back. I could do a full brembo upgrade with bigger discs and calipers. The last and frankly best looking option is the AP racing caliper/rotor upgrade for front and back at around $8500.
I can’t tell from your post but if you are still running the stock calipers they are not up to the task at your HP/Speed level. Not upgrading your caliper/rotor you will never be happy. With more speed comes the need for more brakes. :)

Peter
 

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I do have the stock calipers on the car. I do feel the stopping power is a little weak. It is basically performing at the level of a 997.2 GT3 with the current power levels and that car has much bigger brakes. My race shop thinks bigger discs will fix the problem. I have found several upgrade options that work with my 18 inch APEX wheels. I could do the 997 GT3 caliper upgrade with 350mm discs in front, not sure about the back. I could do a full brembo upgrade with bigger discs and calipers. The last and frankly best looking option is the AP racing caliper/rotor upgrade for front and back at around $8500.
You might also look at the front and rear StopTech Kit ~$5500. I have used ST before and been happy and that is my planned upgrade for my 987.2 TT build.

Peter
 

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I second titanium shims. Usually PSM messes with the rear brakes more than the front. I also insulated the rear lines as they are way too close to the exhaust for my comfort on a 981. DEI makes a tube/sheath that you cut to length and install over the line.

On my 14 Cayman with 380/345mm Brembo GT brakes, Ti shims and rear lines insulated, I boiled Castrol SRF the first two times out. I added the 997 GT3 L-shaped ducts that attach under the LCA and that, with better driving technique, solved my problem.

V6
 

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Discussion Starter #17
I saw that set up. There three levels. The cheapest one may not be enough for us. Did you find any info on weights?
You might also look at the front and rear StopTech Kit ~$5500. I have used ST before and been happy and that is my planned upgrade for my 987.2 TT build.

Peter
 

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I doubt shims will do much, other than make fitting new race pads that much harder.

I’d start with Girodisks.

Also find a shop with PIWIS and ask them to configure your car for Ceramic brakes, even though you don’t have them. That relaxes some of the ABS logic, and is a mod approved for SPC class PCA racing.


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I saw that set up. There three levels. The cheapest one may not be enough for us. Did you find any info on weights?
I am going with the ST60 front ST40 rear. Ran the ST40 front for years on my 8th Civic Si TT car and other than going through pads and rotor rings, which would last until the groves were gone, the calipers held up fine.


Peter
 

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I doubt shims will do much, other than make fitting new race pads that much harder.

I’d start with Girodisks.

Also find a shop with PIWIS and ask them to configure your car for Ceramic brakes, even though you don’t have them. That relaxes some of the ABS logic, and is a mod approved for SPC class PCA racing.


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Agreed on the girodisc suggestion. Cheapest of the options you listed and likely to solve the problem.


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