Why does your 2004 Audi a6 shake when you go over 55 miles per hour?

Could be a bent rim or a broken belt in the tire to say the least. Or it could be something more ie, tie rod, axle, etc. Start with tire it is very common. Could be a bent rim or a broken belt in the tire to say the least. Or it could be something more ie, tie rod, axle, etc. Start with tire it is very common.