I did the 4 brakes/rotors last Sat. on my wife's GM SUV. I know, cool story bro. Don't ask me why but I used OE on the fronts, and AC Delco Professional in the rears, if I could do it again, I would have done OE in the rears too. If you are ever in the same situation, I would avoid AC Delco Professional, and just go for OE. I question the quality.

Anyway, the OE rotors look like BMW OE rotors, in that the whole disc is grayish white with a coating to include the swept surface of the rotor. So as the new pads wear on the rotor, that grayish white is worn away, and the surface looks like what we're accustomed to seeing, a chrome colored surface where pads make contact.

Eventually way down the line especially if pads are replaced without the rotors (common practice except with German cars), the rotor will develop a lip. The lip represents where the pads do not make contact.

For about 3 days, I was kind of annoyed as there was a huge gap on the outer edge of the rotor, I mean substantial. I was thinking hot dang if that huge gap is not being swept, one day it will be a gigantic lip, and that's not how the old/original one looked. Wouldn't you know, after 5 days of driving, now that gap is gone and it looks normal. I looked at shots of the pad where it meets the rotor, and it is in fact pretty much to the edge of the rotor. This implies to me that the pressure is not exerted with the same amount of force, maybe not much force since days later, the coating remained. It's gonna be years before I do another rotor job on my BMW, but I don't remember that to be the case--that grayish white was worn away to the edge on the first drive. Then again, the pads are semi metallic, far less kind to the rotor surface.

The backs, are far worse, where even normally, the pad swept area is rather small in relation to the area available to it on the disc. Yes, I am a geek, I like the details lol

edit p.s. I did the work in a shop with a lift. The tech who was there, when he saw me unbox the OE rotors, I was gonna spray it with brake cleaner--he said you don't need to spray them. When he saw me unbox the professional rear rotors, he said those you do need to spray. And when he saw me banging away on the right front which did not want to come off (original from 2011), he said don't worry, it's physical, it has to come off. Nothing like having someone watch you work!

 

Cool story bro

All the OEM equipment is made by another company (BMW>Pagid, Toyota>Denso) - maybe that's a good way to go for parts

 

Yes, if we're talking the BMW I got genuine BMW, and that has a premium. Most of the other parts, if I can identify them, I go OEM....like say a brake sensor wire that is $28 genuine, it's like $13 PEX, and really the same thing. Or plugs.

With the domestic vehicles imho it's not transparent, but from my "feel" factor, seems like GM OE is better than professional. However, the air filters? OE, and professional, THEY ARE IDENTICAL!!!!! Only one costs a lot more. I put the bags side by side. The GM OE has an additional hologram sticker on it. The AC Delco bag and label are identical.

Some days I wish I had more brakes to do, such a bang for buck job. Well the LS430 rears might be next...I cheaped out with Centrics but they look ok...

 

i have not needed/had any brake service in, uh, forever...
i must be very gentle on brakes.

 

I love new brakes and tires, and being gentle on them is imho the way to go!

That tech just watching me was making me nervous haha I mean you're the pro I get that you know this better than I do. Another mistake I made since I'm usually on jack stands. He said you locked your steering wheel, now you can't move your fronts, which would make it easier to access (the caliper or carrier bracket bolts). I admit I needed his help with the lift. I couldn't reach on the right rear, I suppose based on how I pulled the car in. Cuz the lift arms have to be symmetrical....he just told me to use another point...also, I thought of a Sopranos episode. I could barely get in and out of the vehicle, yet where the door makes contact with the lift, it is protected (dang humans are smart, mad props to Bend Pak). " I think it's time for you to start to seriously consider salads..." dang I could almost not physically get out! (I'm not fat so maybe my car was too far to the left)

 

wife's A5 required fronts brakes recently and I didn't go with OEM stuff - significantly less brakes dust (90% less), but also require slightly more force to brake; I'd go OEM next time.

 

The lip on the rotor you mentioned develops when the size of the pads are not inline with the size of the rotor surface.
I've noticed this with Land Rover vehicles as well as Mercedes. I don't know if it's intentionally made this way but for this reason they have always swapped the rotors out while changing the pads which adds quite a bit of expense to what can just be a pad change.

 

Of course now it's been 6 days of driving, and what was there through 3 days, is gone. Again, I have never looked this closely, but what I observe is the center of the pads are closer to the edge, than the sides of the pads. They taper if you will. Also, I found my old BMW rotors in the garage, and the funny thing is they do resemble the GM rotors, where the inside surface of the hats are not treated. So the surface that does not mate with the hub is severely rusted. But with the BMW, it literally fell right off when the set screw was undone, and I hit the hat with the palm of my hand (the car was like 8 y.o.).

See what I mean about the curvature of the pad? But I feel assured now there will not be a lip as I thought the first few days....now the coating is worn to the edge...

 

This "FNC" appears to be old news, but as mentioned, BMW OE brake rotors have the same appearance, so likely the process is the same. And I can say that in 8 yrs. on the road when I pulled them off, there was virtually no rust on the outside surface. This would not explain, then, that I found severe rust on the inside hat of both the BMW and GM rotors. With this much involved in the production, I feel very foolish for not spending $8 more each, for my wife's rear discs!

http://media.gm.com/media/us/en/gm/h.../1130_fnc.html

 

yeah man. I gotta remember to be gentle and stop tailgating people. That just destroys my brakes.