cander1020

For each of the front brake replacements, after 7,500 miles, the entire front end began to shake during high speed braking. As for the rear brakes, there was no indication whatsoever. The car was having its 20k inspection when the dealer stated that the rear pads were down to 2 mm and dire need of replacement. He said the wear was "normal for such a heavy car"!

sushistrip

I had the same problem within a few thousand miles of installing new rotors and pads on the front. I torqued everything down to spec and replaced the caliper bushings, still had issues. In my opinion it's a fault with the rotor design or manufacturing. Had a shop look at the suspension bushings, twice, and they found no excessive play or wear.

dblang

Turn off the lane departure. It rides brakes constantly to “steer” the car. That is how it works.
I have 75k on my original brakes.

mhoran89

on that note... the assisted cruise control also uses the brakes. it rides the rear brakes (way more than the front) when keeping the specified distance from the car in front of you. using the rear brakes keeps the car flat (versus having the nose dive like traditional 70/30 front/rear brake bias). it allows the acc to do its job and you notice it less. the rears will wear faster due to this if you use the acc on the highway a bunch.

on another note, i picked up zimmerman rotors (not oem) off of ebay instead of going through the dealer and have like 20k on my rotors with no issues. they were much cheaper than the oem units through the dealer.

cander1020

12/23/19 Took the car back to dealer for my 30,000 service (@29,800 mi). At 26,000 miles the front end AGAIN started to shake during sudden high speed braking. So far the car is on it's third set of front brakes and second set of rear brakes--all replaced under warranty. The brake wear indicator has never detected a "wear" issue. Now the dealer is telling me the car needs new rear brakes to correct the front end shaking issue! All replacements were Audi parts from the original Audi dealer. They swear that the lane departure assist and the radar assisted cruise control are not the issue. I do not see where the continued replacement of brake pads and rotors is going to correct the reason why these brakes are wearing prematurely. Anyone have any other suggestions other than dumping the car or getting a big lemon sign put on it??

MP4.2+6.0

Completely different possible diagnosis, from chasing after exactly the same sort of issue in my 2006 A8 W12--vibration/shaking only under braking. For me it happened more under modest to moderate braking--gradually--from freeway speeds. Only on mine, I realized early on it was not the brakes/rotors even though they were on my first suspect list. But that is simple old school common issue spotting, here likely IN-correct.

Net, check front upper control arms with a fine tooth comb. Known weak spot on both D3 and D4. Change out interval on D3 was somewhere between 40 and 70K on average for folks who paid attention to them. D4 design on these remains essentially identical to D3. In turn, an original under spec design of the suspension set up in general that goes back to a mid 90's A4--a car that weighed at least 1,000 pounds less, and that had brake hardware at probably half the weight, and wheel weight at no more than ⅔. I had them replaced under warranty on both my 2000 C5 A6 4.2 and my 2006 D3 A8 W12, both of which have basically that same design. D2 had it too. Only real difference are the air struts for D3 and D4, and eventual D4 conversion to electric rack. A classic "when not if" component that essentially is required long term maintenance.

Frankly don't fall for the usual B.S. quickie inspection either. Have the mechanic unbolt the upper arms at the pinch bolt at the hub/steering knuckle. Then pivot them around the bushing. If there are any deep cracks, they are gone. You really cannot see a lot of the cracking--or distinguish minor vs. major without unbolting--which most never do. I regard any visual inspection without unbolting as not adequate if you have identifiable issues like those described.

Also check the sway bar links in front, anotherl known D4 weakness (yet more than D3). When, not if. That same dubious newer design using the long arm sway bar links now plagues most Audi designs of the era.

What it probably will not be BTW are the tie rod ends. With classic old school diagnostics, these would be suspect too. But my Audi experience (even having changed some) is they rarely wear, especially at sub 100K miles. I tried those first on the D3 BTW, before realizing by control arm bushings had failed ...For the SECOND time...by 100K, even with OE parts. FWIW, the #1 most common early fail point on D3 from my experience on that board, all the way back to the get go.