I have a 2000 A6 2.7T 6-spd Quattro with 174K miles. The car runs and drives fine except if I'm going 70 mph or faster and hit the brakes I get a bad shake, let off the brakes and everything is fine. I had the front rotors turned and the problem is still there, I checked the runout of each rotor on the car and all 4 are at .003 of an inch or less, so I don't think it's warped rotor issue. Any ideas?

 

It has to be the rotors, have you turned the rear rotors or checked them yet?

P.S. Audi stock rotors are made of a super soft metal and aren't recommended to be turned on a laythe because you have to take off too much material to get it level. If the rotor is too thin it will increase the heat applied to the pads and just warp the rotor faster the second time around.

 

I checked the rear runout and they were .003 too. The pads in the rear are about 50% and the fronts have about 75% left. I didn't know the stock rotors are that soft!

 

The cost of manufacturing has gone down so dramatically that for most cars its more cost effective to just replace the rotor.

Shakey brakes are a sign of uneven pad wear. This could mean warped rotors, an air bubble in one side of the lines, or 1 pad being a softie. They way you describe it, its probably something with the brakes.

 

Generally, brake shudder is not warped rotors, it is pad depsition on the rotors. Cheap pads deposit the metallic particles in them onto the rotrs in lumps due to poor compounds that overheat. It is metal, but not rotor metal that causes the uneven rotor surface!. Get new rotors or turn the old ones and buy some decent pads, the problem will stop. I have been around cars a long time and have rarely seen a warped rotor and always on race cars, not street cars.

 

I agree with oldmots. I have seen that sometimes a cheap pad will leave deposiits on the rotor itself. Kind of like when you peal an old sticker off and there is residue left behind and when you rub over it you can still feel it. What kind of pads did you buy?

 

I love older car gurus, a plethora of knowledge always comes from them.

However the metal particles in a factory audi rotor (2000+) has some wierd mix of metals (at least what this german engineer told me when i still worked at the dealer) that makes the pad "bite" the rotor better. The downside is heat is greatly increased and it WILL warp the rotor. I have seen warped rotors at the 15k mark on audi Q7's because of it, that and the pads are metal to metal by this time. Audi also states in their factory repair manual (elsa web) that the rotors can not be turned, they must be replaced. That could be audi BS though, but i don't see why audi would want to pay for repalcement rotors under warranty at the time. They have since removed that from their service plan in 2006.

I apologize for my rambling as i had too many glasses of merlot.......hahaha

 

Very odd that a manufacturer would specify an off-spec rotor other than the mainstream ones, such as cast iron or carbon fiber. I am not an engineer but I would expect that the way to get bite is to use a more agressive pad, not an agressive rotor. A manufacturer that would think backwards like that would worry me.I can't get my mind around the reasoning other than just being obtuse. Specing a soft rotor material that doesn't work well sounds really odd for a manufcturere with a history like Audi.
Oh well, you learn something new every day. Maybe Audi just got tired of plain old easy to fix pad deposition and wanted to rewrite the way you can screw up brakes for themselves.

 

Its wierd i know, im happy as a clam with my heavy rusty cast iron rotors on my 99 GMC sierra I just replaced the pads for the first time at 110,000 miles, rotor was still as level as it was the day it was cast.

 

I'd vote for very slight warp in the front rotors. They get very hot and if they are splashed by rain water or melted snow, they will warp. I had my pads replaced at 104k and now have 170k miles. I replaced the rear rotors but had the fronts turned. For a long time I have felt a very slight shudder in the front brakes -- a very mild pulsing that can be felt if you hold the steering wheel lightly. I am curious to see if it goes away when I replace the rotors and pads the next time. That will probably have to wait another 20-30k since I do mostly highway driving. PS-I switched to ss brake lines a couple months ago and it made zero difference in vibration or pedal pressure.