Intermittent Front End Shaking
 

2002 A8 with only 65k miles will develop significant shaking in the front end and then it goes away. Shaking hasn’t lasted long enough to have a technician diagnose. New tires with speed balancing and new upper ball joint arms seem to help temporarily but the problem comes back. No Ross Tech fault codes, no clicking sounds when turning. U joint? CV axel?

Aluminum can shims wrapped around the hub. I'll have to take find my pictures and upload them. I was chasing a vibration that I couldn't figure out for the longest time until I measured the run-out of my wheels after being mounted and torqued.

All of my wheels had a run out of up to 1 mm / .040in. That may not seem like a lot, but at 70 mph, it made a huge difference.

After carefully installing the shims and torquing the wheels while still off the ground, I was able to get my wheel run-out to under .25 mm / .010 in.

The shims allowed the wheel to be installed more concentrically. Your wheels could be balanced perfectly but if they aren't mounted perfectly centered over the axis of rotation, you'll feel a vibration come and go at random as the wheel's imbalances cancel each other out or magnify as you drive.

Thank you for replying. Where would I be able to pick up these cam shims?

You have to make them. I really mean using an aluminum can. A beer can, soda can, energy drink can. Any can made of aluminum. I had to use a small metal ruler, my wood workbench, and a very sharp X-Acto knife. Like I said, I need to dig up some pictures so I can fully explain what I did.

Tie rod ends...inner and outer...when worn will give you a random shimmy & vibration.

I assume you are running stock rims. The wheels are hub-centric. They center up on the raised circle in the center of the hub, not on the wheel studs. If you are running later model or aftermarket rims, your wheel hub bores might be larger than the centering hubs on the disc face. A $20 caliper from Harbor Freight will tell the tale. When I swap out to late model potatoe peeler style rims, i use a hub ring like these:
Warped or ovalled rims?

Wheel bearings good?

Lower control arms?

Blown shocks?

Thanks for the insight. Yes, I am running on stock 2002 wheels. Bearings were recently checked when the ball joints were done. So looks like I'll be inspecting the tie rods next.