Steering wheel shakes and a little smoke underneath car on 1999 Audi A8 Quattro

When I drive 55-60, the steering wheel shakes..not too terribly, but enough to bug me. I got my 2 front tires replaced today (with balance), and it still does it.

2. When i stopped driving and looked under car, I saw a little smoke coming from the center. Should I be concerned?

Asked by for the 1999 Audi A8 Quattro
its hard to comment on the smoke without being able to see it or smell it!
Try rotating the tires front to rear and have those tires balanced so if that improves things. Are the tires a known good brand or a cheaper tire. DO the tires spin absolutely true, no weaving side to side?
Check for play in the suspension bushings, tie rod ends, steering rack............
My 2001 A8 had trouble with the front brake calipers. A caliper would seize up occasionally and result in vibration and a very hot rotor. It also caused uneven tire wear. I had to replace both front calipers (and rotors) and the problem was fixed,