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There is some controversy as to whether or not these are wear indicators - I have not been able to get a straight answer on multiple forums or from Porsche technicians. They can most certainly be seen on a new vehicle (my GT2 purchased used < 195 miles on it had them.) However, many believe that the circles get bigger with time.



Look for cracks between the vented holes. Here is some additional info about checking PCCBs:

 

Hair line cracks on my 996 GT3's PCCB and was told by a few "experts" that as long as the cracks didn't span 3 holes, it's okay, but it was close to reaching 3 holes.

 

I think the main thing to look for, from what I've been told, is to ensure the pad are replaced before they get to 50% wear. Supposedly if you do that, absent hard tracking, the rotors last a long long time.

 

My Turbo S has no such 'circles' on the discs and I have never seen them on any other. I checked with our VP Engineering (StopTech) and his reply after revieiwing this thread:

"I don't know of any reason to include that round feature in the parts for wear indication. As you have seen the "wear limits" were originally mass (or mass loss), cracks, surface eruption (an indicator of oxidation limits being reached), size wear indicators, and chips most likely due to damage from careless wheel installment.<O</O
<O</O

I believe the circles are due to machining out a flaw that is detected, bored or drilled to remove and then a slurry (the same material as the original build) used to refill that space. The same materials being used doesn't mean it would not appear different.<O</O

The test of that theory would be a check of locations: does it always appear in the same place or is it more random in radial position? Random also includes it presence on one rotor on a car but not all or any others. If it is repeating in presence AND position then maybe there is another reason."<O</O

 

From Porsche's TSB regarding IRON brakes not PCCBs:

 

My tt is 2008 model with PCCB, i have 30k KMs on it now. When should i look for brake pads?

 

Have you measured the pad thickness? That usually will tell you when to replace.

 

no i havent, i will

 

Great thread, great info. I've read the 50% thing above too.

Could anyone who has looked into this more carefully than I have comment on this? Bob? Fact or rumor?

 

Before tracking my car the 1st time I did a lot of research on PCCB's. I'm not going to get into the whole "they can't be tracked" or "yes they can be tracked". All I'll say is that if you dig deep there is some pretty interesting info. out there.

Now, with regards to pads. This was also part of my due diligence. I spoke to several shops that actually RACE porsche's - TPC, GMG, and the guys at the former Farnbacher-Loles. To a man, they all told me the best way to increase the life of PCCB discs is to NOT let the pads get below 50%.

I was about 50% wear at around 30,000-35,000 miles on my car and changed them out. Reasonable insurance as far as i'm concerned.

 

Are there any good aftermarket ceramic pad manufacturers or did you go OEM pads? I've searched and have been a little confused over the aftermarket pads I have come across so far...

 

I went OEM. I've read some conflicting things about aftermarket pads - I would think a more aggressive pad will be harder on the rotor, no? I'm no track junkie so OEM seemed like the way to go.

 

I've heard the exact same thing. I don't have anything solid from Porsche, it's all hearsay. On that note, even though the front discs do the lion's share in stopping, the rear's are subject to faster wear. Should probably check both at the same time.

 

When I purchased my 997tt it had 19k miles on it...The dealer told me they replaced the pads on the pccb as part of the cpo process...So I'm not sure if they did it to cpo my car or just because they were worn...