[vilshofen]

After the 2nd and now successful re-build of my front calipers w new pistons I measured my track pads (PFC 08's) and found uneven wear. At one end of the pad, it is 7.5 MM of material left and at the other end (going left to right), there is 8MM left.

Makes me think that if I try to continue using them, since they are effectively slightly slanted, the contact of the pistons will also be the same on the backing plate. This would seemingly cause a lack of uniformity of the orientation of the piston within the bore which could prematurely wear the bore as a whole. I say this because the pressure exerted on the backing plate via the piston would be via the edge that is touching (since the pad orientation is not flush but slanted)

Does anyone have an opinion on this matter? I already bought a new set of pads but wanted some of you to challenge my logic.

 

[Boristhespyder]

First off, the drawing is misleading because we are talking about .5 MM, the representation makes it look more severe. Just WAG / opinion: If anything the rotor surface would wear differently or grove and even that is unlikely with a .5 mm shift. You answered your own query, pads are cheap so you replace them to prevent any future damage via a lack of doing so. Having said that, I'm confident parts more compromised than this are going back in but they are going back into cars people don't care about beyond point A to point B, some would sand it flat, reassemble and park it.

 

[ajahearn]

I have noticed that the leading edge of my pads is worn down more than the trailing edge which is what you describe - 0.5mm is about right. But as Boristhespyder points out, that is not the thing to concern yourself with - pad thickness is the most important measurement. I understand your concern as you have rebuilt the calipers but it seems they are functioning as designed.

 

[vilshofen]

Appreciate the feedback. Yes, the drawing is a bit misleading for the sake of showing the offset position of the pistons contacting with the backing plate. The small details like this interest me as I am always asking "why is that?" or "is this tapering expected based on either some design or use element?"

There are quite a few out there who have noticed the same thing but I've never seen anything definitive on the why, or if it is a servicing or design defect. I know at the end of the day, I've lived with it for a few sets of pads, but I'm still trying to figure the "why" on a more detailed level vs the possibilities I've thought of.

One thought is that before the re-build, either the leading or trailing set of pistons was not releasing as much as the other and hence the tapering. That's just a guess and I was hoping for some more input from the forum, or perhaps if we are lucky, a Brembo engineer could provide some feedback!

 

[ajahearn]

I attributed the uneven wear to the leading edge having no material in front of it to help reduce the force whereas the trailing edge has all the material before it.

 

[vilshofen]

I attributed the uneven wear to the leading edge having no material in front of it to help reduce the force whereas the trailing edge has all the material before it.

Now that's an interesting theory and makes sense. In some of my research, I found that having the 2 piston sizes (36 and 40MM) was specifically for the trailing edge vs leading-edge consideration! I went ahead and sent a note over the PFC to see if their engineers would be willing to comment.

 

[Craig911]

I have 3 new sets of these same pads if needed. Kept in air conditioned home, unused. 3 sets PM for price.

 

[PorscheGreg]

Did PFC ever provide an answer to this query? I’ve also heard that piston sizes are uneven to account for the differences between the leading and trailing edge of pads.

Has anyone ever heard of “flipping” the pads to even out wear?

Also, curious to know if the uneven wear occurred for both wheels or just one. If only one, then perhaps something that the caliper rebuild might improve, but if both, then I would guess it’s the normal wear pattern.

 

[ledbette]

0.5mm isn't much. I'd swap them to the other side next time and it should even-out the front-rear wear after a day at the track.