Had the family in the car earlier and noticed there was a humming sound coming from the rear wheels. Doesn't seem to appear evident when I'm on my own, just with passengers in the back. It's not unbearable but it is noticeable. I'm guessing it's the wheel bearings, or wheel alignment? What am I looking at with wheel bearing costs from Audi? Is that by any chance included in a Geometric check (wheel alignment) that Audi do?