BobbyC

For anyone who may care, I measured my PCCB rotor thickness today...

car has 22k miles, approx. 75% street; 25% track

Actual (mm) Minimum Factory New

LF 34.2 33.8 34
RF 34.2 33.8 34
LR 28.1 27.7 28
RR 28.2 27.7 28

As you can see the actual thickness is > what the factory "new" specs are.

PogueMoHone

The wear pattern on the new generation disc shows up as a hologram (except it is not 3 dimensional) on the disc, these are about the size of the quarter and spread randomly across the face of the disc. No need to weigh them or measure them.

flash1034

Huh? Please explain.

Flash

PogueMoHone

When the disc need replacing, you will the above pattern.

C.J. Ichiban

it looks like a circular cross section...are you saying that it is necessary to replace when you see it or when you no longer see it?

John Boggiano

The wear indicators are made of less-heat-resistant carbon-ceramic. They will form what SGL calls 'holes' - by which I think they really mean 'pits' as the disc wears. They don't need replacing just because the indicators become visible, although you do need to remember that the pits could fill with pad material and so not seem as deep as they should over time.

cello

^ Thx John; but when, then, do you need to replace; ie at a certain depth?, when you see too many?, when the rotor losses enough mms?, etc.

roberga

the shops have photos in the manuals that they use as guides. You will know because the rotor feels like sandpaper and the pads go in a blink of an eye.

C.J. Ichiban

well in either case I'm glad I'm not needing to replace for a while yet

sws1

Are those holes visible all over the place, or just in certain spots? I thought I saw a circle on my rear rotor (bigger than nickel, smaller than quarter) near the outer edge.

I can't imagine these need replacing already after 6k miles.

MarekN

Yes, that´s it. It´s not a hole, but a disc which you see well only from a certain angle. I think that you don´t even have to use the disc as a token. When the rotors are thrashed, you can tell right away from the various little places where the surface material is missing in bigger chunks. The brakes still work after that, but the pads are hurting. The PCCB rotors have a surprisingly thin surface, but I guess this is in line with the extreme hardness, in which case under regular circumstances there is no real need to have it any thicker. From what I have seen so far, it either stays on the underlying structure and you have a long-life rotor, or it chips off and you are in trouble.
We have to look at PCCB as something that cannot be compared to the regular method in which iron brake rotors are engineered. It really is very different and therefore even the way you approach the method of measuring wear or forecasted longevity can´t be compared.
With iron brakes you know exactly where you stand because the only thing you measure is the thickness. You can get glazed surface, baked-on pads, etc, but the main thing is the thickness.
With ceramics it is a little bit more complicated. But I guess we all know that by now.

sws1

So then, the fact that a wear indicator is visible doesn't mean anything?

Material chunking or cracks between the holes are the signs of wear?

MarekN

I didn´t mean it that way. It is something that serves the need to have a proscribed procedure that can be used in a unified way by all the centers across the world. My point was that you can tell the condition of the rotor just by looking at it, in other words you don´t have to search for the discs to know that it needs to be replaced.

There are what appear to be minute cracks all over the surface of the rotors, they even have a special pattern around the holes that freak you out at first, but these are not the same as regular cracks on iron rotors. I think that when you see a bad PCCB rotor, you will know right away.

Special note: please see ceramic rotors from Brembo, as on ZR-1, Ferraris, Astons, these have a completely different color and surface structure in comparison to PCCB mady by SGL. It would be interesting to know why.

MJones

Patent 6,776,265

Device for indicating the total load in the case of brake disks made of carbon-fiber-reinforced ceramic material

Abstract
A device can indicate the total load of a brake disk made of carbon-fiber-reinforced ceramic material. In order to create such a device, which can be used for brake disks and other friction elements made of carbon-fiber-reinforced ceramic material, an indicator element can be provided in the brake disk starting from the friction surface. The oxidation stability of this indicator element is reduced with respect to the material of the brake disk.

sws1

After holding a flashlight against rotors, I realized I could spot the disks all around. You have to look at the right angle. Sometimes you can't see it at all. And if you get real close, you can see that the material has a slightly different texture or pattern than the rest of the disk.