kgd_007

My sensor light on the front pads also came on early. I drove it for at least 2,000 miles and it still had lots of pad left when I changed them. They could have easily went a couple thousand more miles. The rotors were less then halfway to the minimum thickness from the new thickness so I just swapped the pads. Didn't turn the rotors even though they had a very slight lip on the edge. They have worked good as before and don't make any noise. I did take it easy the first few hundred miles.

You could buy all the tools you need including the Vag-Com cable and still spend less doing it yourself than going to a dealer / independent.

DTHREE

Gee - that's kind of it. Shame it doesn't share the measurements with anyone or anything.

Bangerla

Plug in VCDS and read the thickness... It is not that selfish, it shares if you know where to look.

GnatGoSplat

I've no experience with the A8, but I've been a DIYer working on cars for over 20yrs. Why would you need to replace the rotors if they're not warped? Or are they warped already? Usually rotors that warp frequently indicates sticking sliders.

Mister Bally

You would need to replace the rotors if they have worn down beyond the minimum thickness specification. Too thin and they cannot dissipate heat properly leading to brake fade when you need them most. Also, too thin a rotor coupled with too thin a pad can cause a caliper piston to pop out instantly losing 50% of your brake fluid and braking power.

mishar

+1

I am just a bit less optimistic about 50% lost of brake power. If oil start leaking at the front one will loose 100% of concentration because of sudden brake pedal dip, 90% of directional stability and 90% of braking power.

MP4.2+6.0

coming out unless there is basically just plain no rotor there, in which case there are a whole lot more problems... The piston reaches way deep in and the seal is on the bore part of the caliper casting pretty close to the edge, at least in front. I have disassembled one in front for a project, and other ones about the same as the back that have been pretty much the Audi standard issue for 20 years other than the electric parking brake add on.

GnatGoSplat

Yeah, I don't see the piston being able to come completely out as long as the rotor is present and still resembles a rotor.

Of course, it's always best to follow service recommendations and pull out the old micrometer and chuck the rotor if it's even a micron below recommended thickness specs, but I've never found that kind of attention to detail to be all that necessary. I don't usually even bother to check the thickness unless they are warped (causing pedal pulsation) or showing deep grooves by loss of pad material.

mishar

I am not so sure you are right here. New pads have 15 mm of a friction material. If both of them are to the metal it makes 30 mm. If we add 6 mm of an extensive rotor wear (could be more on 34 mm rotors) and at least 1 mm that allows assembling of all new parts, it comes to 37 mm of a piston travel before back piston face reach the seal. Is there that much travel?

Another disaster scenario is that only one pad is to the metal. That would allow metal part of it to slide out between worn rotor and caliper allowing extra 5 mm of the piston travel.

mishar

That just proves that even 200 years of experience are not guarantee that one know what he is doing. Sorry, but we are talking about brakes here and some uninformed people may follow your example.