DGH-Fahren

Rennlist Members : I have a 2011 Cayman S with a PDK. For some time now I have been experiencing significant rear brake heating, when driving on the track. I am hoping that a few forum members have found solutions. Here is the background.

For the 987.2 cars with PDK, Porsche's Automatic Brake Differential (ABD) is always on. ABD's effects can be reduced in Sport or Sport plus mode, but it is always active. This means that during the neutral throttle and acceleration phases of most corners ABD will attempt to correct the slip angles, as it sees fit. Consequently, the rear brakes are often on, while the gas is also on ! Heat results.

I can think of 6 ways to deal with this problem ...
1) Hire a coach and change technique to deal with ABD.
2) Upgrade to GiroDiscs and track pads from stock rotors and pads.
Note - changing just the pads is not going to matter, because the brake energy dissipated as heat is not going to change. That is, if you slow the car by 10 mph with pad A or pad B - the net heat is the same … E=1/2mV^2 .
3) Add some cooling ducts.
4) Upgrade the calipers, rotors and pads to Brembo or StopTech
5) Combinations of the above.
6) Get rid of the car, instead of spending more money on it.

Who has solved this problem and how did you do it ?

Thanks for your perspectives.

Ubermensch

I went with #2 and #3 from day 1. I've never had an issue running PFC pads. A few weeks ago I did seven 30 minutes sessions at Laguna seca and had no issues with heat in the brake system.

DGH-Fahren

Thanks for the reply ! Here are a couple of follow-up questions.

1) I assume that you have a Cayman S 987.2 . Do you always drive the car in Sport or Sport Plus mode, or do something else, to help reduce the effects of ABD (brake steer) ?

2) Are your track sessions pushing for qualifying times, well under 2:00 minutes per lap at Laguna Seca, or do you just drive for fun and smoothness, or perhaps something in between ?

3) The GiroDisc solution is easy. But, what did you do for cooling - add GT3 or GT2 ducts, or something more custom and effective ?

Thanks again !

Harvey in FL

On my 981 CS, I was having over heating on my rear calipers. I added titanium shields and this helped. Also, added shields to the front calipers.

I was running with Giro Disks and PFC pads.

Harvey
National PCA HPDE Instructor
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2015 981CS - PDK, GT Silver/Black
2008 997.1 C2 - 6 Speed, Meteor Grey/Sand Beige (gone)
2000 986S - 6 Speed, Arctic Silver (gone, but not forgotten)

DGH-Fahren

Thanks for the reply.

Right … this sounds like the same problem that I am having. Automatic Brake Differential (ABD) comes on and corrects the car with the rear brakes … while the gas is on in the mid and exit phases of most any corner. So we both get extra heat in the rear brakes.

In other words, I assume in your 981 that you cannot turn off ABD, just as in my 987.2. Is the effect reduced in Sport or Sport Plus modes ?

BTW - See the MS Word Summary, from the Porsche website, for how PSM, ABD and other systems operate. This is for my 987.2, yours 981 is probably similar.

Your post also tells me that the Giro Discs are not removing enough heat, since the Titanium shims helped keep it out of the calipers. Would you agree ?

Thanks again !

Tom Tweed

The ABD intervenes because of wheel slip, and this is a common trait of the mid-engine cars on corner exit, compared to rear-engine 911, because of weight distribution. You can't hammer the throttle quite as hard when the inside wheel is still light or it will spin. A smoother, lighter throttle application can help somewhat in preventing wheel spin, but won't help to improve lap times.

Doesn't everyone who tracks a car with Sport Chrono use Sports Plus on the track? Beside lessening PSM intervention, it has benefits in shifting behavior and throttle response.

The best answer to this problem is in the last paragraph of that document:
Does your car have a LSD? There were very few 987.2 Caymans optioned with it. I had to search for over 3 months to find my 2011 S with option 220-Limited Slip Rear Differential Lock. If not, the best thing you could do is install a Guard LSD if you track your car. By limiting wheel spin on corner exit, the ABD will intervene less, plus you have the additional benefit of greater stability under heavy braking.

Better brake pads and better cooling are good ideas for any track car, as is isolating brake heat from the fluid, which is what titanium backing plates are doing, but eliminating the wheel spin through a mechanical LSD will do the most to cut down on adding heat into the system from ABD intervention and allow you to make heavier use of the throttle on corner exit.

That's my $0.02,
TT

DGH-Fahren

Let's regroup a bit - a summary of everyone's good ideas follow.

The only thing I'll add at this point is ... Some posts have mentioned various upgrades to remove more heat. For these changes were they enough, and how hard do you push your car - fun, red mist, or something in between ?

Thanks very much for all of your thoughts !

---------------------------------------------
REGROUP

At the start of this post, I summarized the following options to reduce brake steer intervention by ABD, and the extra heat and wear that this causes ...

1) Hire a coach and change technique to deal with ABD.
FORUM RESPONSE - Go lighter on the exit throttle ...

MY THOUGHTS - Yes, drive different - but that also limits improvement.

2) Upgrade to GiroDiscs and track pads from stock rotors and pads.
3) Add some cooling ducts.
4) Upgrade the calipers, rotors and pads to Brembo or StopTech
5) Combinations of the above.
FORUM RESPONSE - Use Sport or Sport Plus modes to tone down ABD. Try Giro discs and titanium pad shims. Consider adding a limited slip differential (LSD).

MY THOUGHTS - I already run in Sport or Sport Plus, and my 987.2 has the Porsche LSD. So, if I keep pushing the car, it looks like I'll need to spend money on the heat problem. The question now is what's enough ? Would you guys be satisfied with Giro Discs, Titanium pad shims, and GT3 or GT2 cooling ducts ? I am only going to upgrade once - measure twice, cut once.

6) Get rid of the car, instead of spending more money on it.

Ubermensch

Sorry, I forgot about this thread and didn't get a notice that there were replies. Responses to your questions:

1) yes, I have a 987.2 S
2) it was my first time at Laguna seca so I was far from the fastest on the track. I was running low 1:50's and had a few 1:49's if I recall correctly.
3) I installed gt3 brake ducts up front and modified turbo ducts in the rear
4) I do have the stock LSD
5) I actually rarely run sport plus due to higher temperatures (oil and water and presumably pdk). I've trying to keep things cool to avoid problems with the PDK until I have time to install a cooler on the differential. I do prefer sport plus but it's not a major hindrance to run sport only.

I do experience the brake steer you've described but don't have any signs over overheating. In my 996 I got used to dealing with a soft brake pedal on hot days with low pads but so far I haven't had an issue with the Cayman.

-Shawn