Thanks; that's a VERY nice article on PSM! So it appears PSM could brake either front OR rear brake, and I had it "slightly" backward above: In oversteer situation, PSM brakes the outer front wheel, not rear.

Also note the part about engine blip; sounds scary. Imagine feeling rear of your car going out of control in the snow, accompanied by engine roar even as you're lifting the gas pedal!

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http://www.deter.com/porsche/PSM.txt
This enables the PSM to detect oversteer and
understeer. It basically determines the slip angle of the front and rear tires, or more simply, when the car is not going where the steering wheel is pointed. Oversteer is minimized by automatically applying the brake on
the outer front wheel in a bend, slowing the rotation of the car; understeer is minimized by applying the brake on the inner rear wheel, speeding the car’s rotation. No driver will be able to do that until Porsche develops a car with four brake pedals.

However, PSM is not only a braking system. If you lift off the throttle in a low traction situation (wet, snow, etc.) and the back of the car gets loose, PSM will increase the engine speed (blip the throttle) to keep the car in line. Also, if traction is low, PSM can use engine braking (EDC – engine drag torque control) to slow the car. PSM can calculate the amount of available traction by comparing wheel speeds at all four corners of the car.
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Yes that's what PTV does, braking the wheel to control torque.

I remember being a little disappointed with PTV (not that I know anything much to be disappointed about LOL, it's just there was that GTR, seemingly a technological marvel). Before the release of 997.2, I and some other people thought it was a complex system that makes use of the electronic differential to vary torque sent to each wheel, not a simple wheel-brake scheme.

 

the 3 circles of the gen 1 disc material fused with the gen 2 discs (997) , if the circles go back then you overheated the disc, thats how porsche can tell if you trak it, why change at 50 % wear on the pad whats the reason behind it, no where in the manual it says that, just curious as to what the logic is with teh 50 %?
btw i have pccb on mine, and i have some surface cracks on the rear, and you are right the rears wear faster as the rear brakes are biased in 997

 

I have just found that my rotors have those circle marks on them, my car has 30k kms of which 20k is normal street driving and the other 10 highway runs, i don't think this is an indication of wear. But what is it?

 

So I just finished my second DE yesterday with 2,200 kms on the odometer and noticed I have that mysterious "round dot" on my rears. Anyone have an answer as to what it really is? It can't be a wear indicator as I have so little use out of the brakes with so few kms. If it is then it better be under warranty. All this negative press has got me paranoid.

 

There is more than one small round disc embedded in each cc brake disc - at least three from what I can determine looking at the brakes on my car. I was told by a local Porsche mechanic that these small discs consist of "generation 1" disc material. If the brakes have been run very hot they should show the effect first, before the rest of the disc shows it.

 

please read post # 33, the circles will progressively go dark when over heated, mine are slightly visible , if they go totally black then you have over heated your disc, this is not a wear indicator...

 

I read your post but what do you mean by "the three circles"?

Isn't it difficult to over heat the PCCB's? I have only tracked my car twice and the last time was in the pouring rain.

 

Guys, I asked a few of porsche test drivers and got all information about PCCB. Those dots are very normal, no sign of wear. What you need to be aware of is brake pads which might wear off and not show any warnings. In my case they wear out unequally so one side the pad was half the way and other side was almost finished. The sensor is in the middle so I wouldn't get any warning

 

I've followed all recent debates on PCCB. Whether to order them or not, when to replace the pads etc.
The explanation from Milou seems more than reasonable why it would be better to replace the pads at 50% wear. Like that you'll prevent uneven wear on the pads to cause damage to the discs.

Anyone else has seen the same result when replacing PCCB pads?

 

Regarding the circles that may or may not indicate wear or overheating, actual documentation seems not readily available? I have spoken to several dealers, techs, race team techs and braking engineers and no one can varify either of these claims.

Porsche, it seems, has no published materials specific to the inspection of the discs and the circles.

Some posters are certain of their knowledge--can you please provide documentation for the community? Thanks!

 

How thick are the pads initially? Is there a 50% mark on the pads or do you have to measure?

 

In my last car with Carbon ceramic brakes ( a Corvette ZR1), the rotors were checked for wear by weighing them. There was a minimum mass tolerance for the rotor. I' m not saying that's how the Germans do it...

 

Great thread, quite informative...I have a 996 GT2 with Gen 1 PPCB and no PSM, torque vectoring or any of that stuff...do the same wear patterns and practices apply to me? I am looking at getting a back up set of PCCB rotors from an '09TT which are the 380mm F and 350mm R setup with Gen 2 PCCB...

as for pads, I've been told Porsche offers both a street and race pad for PCCB cars either Gen 1 or Gen 2 discs, the Gen 1 have been updated in part numbers apparently for recommended pads. Does the replace at 50% advice apply to the factory race or street pads, when considering a fairly simple (non PSM, PASM, PTV etc...etc...) car like my 996 GT2...?

thanks

 

From my knowledge on PCCB i can tell the following...
1)I am aware that small circles are wear indicators...there are three indicator signs...small circles on the outer diameter of the disk,that indicates wear of 30%,small circles on the center of the disk,that indicates wear of 60% and small circles on the inside of the disk,close to the hat,that indicates the disk has to be replaced...
2)OEM pads are a combination of solid braking power without overstressing the disk...Of course there are better pads (harder material) in the market resulting in better braking under pressure...and shorter lifespan of rotors...
3)it is better to replace PCCB pads at 50%...this is due to the fact that as the pad wears,the material is getting harder and so the disk is more stressed...