My results did not turn out satisfactory as Mark (Brembo) indicates it will. When I made the change, I felt there was far greater than 2% bias difference. I upgraded to the Brembo 6-piston monobloc calipers with 355 (350?, I forgot) mm rotors and PFC 01 pads. It seemed the front brakes then began to do the lion's share of the work and I was going through a set of front pads in 2 track days which was unsatisfactory to me. I machined a spacer, bought 997-length bolts, added 997 rotors to the rear and Pagid Black pads, using my 996 calipers and front brake life became somewhat better. I then added the Brembo GT kit to the rear with PFC 06 pads and I have gotten almost 6 track days out of the front pads and they're still not completely gone.

 

Al, the above is with respect putting the OEM 6-piston brakes and 350mm discs on the car. With the GT kit with M6 calipers and 355mm discs, the balance is EXACTLY the same as OE. This is based on piston areas and effective radius, and assuming equal pad coefficient of friction front and rear, as it is with the OEM setup.

You say you ran PFC 01's in front but no reference to the rear pads. The PFC 01 is a top-level racing pad with a coefficient of friction about 40% higher than a typical high performance road pad, so right there you would have moved the balance greatly to the front unless you had a pad with equal coefficient on the rear. So your results don't surprise me.

 

I first had Pagid Orange on the rear and then went to "01's on the rear. The F/R balance did not return, even with the same compound front and rear. I guess I don't understand much about brakes but it seems to me that the addition of 10mm radius to the torquing capability plus the larger swept area of the pad would in and of itself bias the system differently than stock.

I was going through a set of custom-made 01's in the front within a weekend with both PFC 97's and 01's on stock rear rotors/calipers. I always consider them used up at 4-5mm remaining. I believe the fronts start out at 11.1mm from Porterfield. I ran the GT front kit this entire season past and got a chance to try several different rear compounds before finally moving on to the afore-mentioned changes. I even tried a set of the Ferodo 3000's, I believe it was, recommended by a Brembo representative and I chewed them up in 45 minutes of track time as well as faded them so badly that I went off the track braking for turn 10A at Road Atlanta. Got some pea gravel between pad and rotor and ruined the front rotors as well. I never had pad fade with any of the other fronts I tried.

 

You are neglecting the piston sizes in the calipers. The balance did not return most likely because the rear pads were never up to operating temperature, so they never achieved the high coefficient that the fronts had.

 

[quote=msv;2179740]Al, With the GT kit with M6 calipers and 355mm discs, the balance is EXACTLY the same as OE. This is based on piston areas and effective radius, and assuming equal pad coefficient of friction front and rear, as it is with the OEM setup.

Maybe I'm too thick-headed to get this but in your quote above you state that with the GT kit and 355mm discs, the balance is the same as OE. I have the GT kit with 355mm rotors and at one time ran the exact same pad front and rear, PFC 01's. Are you speaking of a a GT kit on all 4 wheels? That part wasn't made clear in your post. In my posts I was talking about the problems I had before going to GT on all 4 wheels, not afterward.

 

Al, I was speaking of the 355mm M6 GT kit on the front and the original rear brakes. The front kit does not change the front/rear brake distribution. In my previous post I made referece to you having run the PFC 01's on both front and rear, and I speculated that your rears were never up to the operating temperature that the front pads were, therefore not achieving the same high coefficient of friction either. This would result in a substantial shift of the balance to the front of the vehicle.

 

The brake system itself is biased properly, it's about finding the proper combination of pads that you like as a driver.
(1) for desired feel
(2) for wear rates that you are happy with.

The trick for matching pads is not necessarily to use the same compound front and rear, (they obviously run at different temperatures front to rear therefore producing different CoF front to rear), but rather try and match the CoF closest to the actual operating temperatures.

 

Holed rotors fro track use make ZERO sense. An absolute waste of time & effort.

 

Not necessarily.
There's a weight advantage, almost another 1/2 lb. actually.
And if you're using a high quality disc with good metallurgy and build quality (like Brembo), in combination with an appropriate pad compound, there's not a single disadvantage.

We're not talking about crap rotors that are backyard drilled with super aggressive race only brake pads. The old rumors of drilled rotors cracking don't apply to any drilled rotor.

And to my understanding this is ONLY for the 330mm 996 turbo application. If they're not going to make a rear option for this car it's the only way to have matching front and rear discs. I guarantee 90% of the people who buy these discs will only be tracking a few times a year at most.

 

Yea, uh no... Your assumption is negated by the fact that the OEM Brembo rotor gets hosed up real good by the pagid Orange pads...

I'm a believer in the Brembo solution, ONLY because I've seen their aftermarket rotor in action on my friend's LG Racing Z06. But let's not spew fiction and distort fact... MOST crossdrilled rotors are not sufficient for repeated trackday abuse!

There are way more of "us" who have first hand experienced this "oem crossdrilled" failure... Sell that bunk somewhere else...
Mike

 

Exactly. Holes = a ****ty setup for track use.

And as far as different pads F&R "therefore producing different coefficients of friction" jeezus H where did you hear THAT bull****??

 

CALL TODAY! Nah.

 

Just an FYI, the OEM Porsche discs are not made by Brembo.
(just thought I'd clear that up first)

The majority of the people I deal with use their car for dual purpose, daily driving or weekend cruising with only the occasional track day mixed in a few times a year. There is nothing "bunk" about endorsing a product as long as the recommendation is appropriate for the intended use. The OP titled the thread "Sorting truth from Fiction", and the truth is that drilled rotors do not crack simply because the are drilled. More often than not it's either a poor quality and/or improperly drilled disc, or a temperature related issue that would have also had a similar effect on a smooth or slotted disc as well.

Before you continue to second guess my post, if we were talking about a brake package for track use ONLY, then I would also be discouraging the use of a cross-drilled disc. I specifically mentioned that the key to avoiding problems is using an appropriate pad compound for a reason. It's much more an application and usage issue than a design issue. The point that I was trying to make is that you shouldn't be afraid of a drilled disc just because it is a drilled disc.

 

Wheels Boutique guy, {sorry I don't see your name anywhere}, what track pad combination do you suggest with the Brembo rotors that will give proper temps in front and rear?

 

I'd run a Pagid RS4-4 in the front and a RS29 in the rear.

The RS4-4 wont see any pad fade until over 900degrees and it's super friendly to the cross-drilled disc. The RS29 has a higher initial torque at ambient temperatures so the rears will be doing more work with the lower temperatures they will see.

Obviously pads are very subjective and everyone has different preferences. This is a very streetable setup with no need to be changing pads for the occasional track day. I have a few different customers using this combo on OEM Turbo brakes, and I recommend a similar setup for the Brembo GT kits.

If you have the ability, and the time, the best thing to be doing is monitoring temps when you are at the track. That's the best way to sort out friction issues and keep track of what's working and what's not.