Hey there all...
I've got a vibration that only starts at 65MPH, and the lets up at 80MPH. I can see the headrest of passenger seat shaking, drink in cup holder shaking, etc. This is only while cruising, no shuddering under braking, no noise at lower speeds.

Here are 5 key facts/contributing factors to consider...

1. I started noticing this after doing the A8 rotor/TT carrier upgrade. Brand new rotors, brand new pads. I also painted the carriers and calipers, so I cleaned the hell out of them.
QUESTION: Could this be a function of the carrier bolts or caliper bolts not being torqued to the correct spec???
QUESTION: Could this be caused by debris left on the wheel hub, or maybe the rotor isn't sitting correctly on the hub for another reason?

2. My first move was to get the wheels balanced. Didn't fix it.
QUESTION: this has all the indications of a balance issue...is it possible the shop just F-ed up the balance?

3. Got an alignment done. Knew it probably wouldn't fix it, but I was due for one. No luck.

4. Brake pads have been bedded. Again, braking is smooth. I wiped down the rotors with rubbing alcohol prior to installation, but later learned that I wasn't supposed to.

5. Tires are brand new as well.

So yeah...any thoughts? I felt a LITTLE vibration prior to installing the brakes, but always chalked that up to normal gritty roads on boston highways. But it is MUCH more acute after installing the brakes. Would any brake components contribute to this? If not the brakes...any other part of the suspension that should be suspect? I didn't see anything out of the ordinary while the car was on jack stands.

If you're curious, I put up some pics of the brake project here:
July 4th brake project - A8/painted

Thanks for any feedback,
-G

 

I have the exact same issue and tried the same things. Did you come up with a solution?

 

Could be a Bad TRE or CV Joint. They will cause Vibration at high speeds if they are faulty.

 

Thanks I think it's coming from the back, and I checked the CV joints when I replaced both rear wheel bearings.

Wondering If I have a dinged up rim. Found a guy with a good one for $20 so I'm going to give it a try.

 

if it was a dinged up rim they should have noticed it / told you about it when they did the Wheel Balance

 

I'm tracking down a very similar wobble myself. Took my car to sears for a balance/alignment and they told me I have 4 bent wheels lol...

I'm going to be picking up a set of winter wheels/tires here shortly, so we'll see if that's the issue or not.

 

WoW 4 bent rims? LOL you sure the guy doing the balance / alignment didn't have a lazy Eye? haha

 

Did you check the inner CV joints? Most people only look at outers, but worn inners will cause vibration at speed.

 

lol yeah thats what I said. He goes "yeah they look like cheap aftermarket wheels, not factory, thats probably why they're bent"

Ok ********....

I'll take a look at mine this weekend, never even thought of that. Thanks man!

 

I already said CV Joints Jeremy why you double posting HAHAHA