I forgot to mention...

If there is weight in the back seat or trunk, the vibration feeling is worse...

Are you sure it's not the front end? Many times a bad CV joint will exhibit these symptoms. Also, out-of-balance wheels will do it, but with new wheels, your balance should be OK. I mentioned this to my mechanic, who says the CV joint looks fine. The shimmy/vibration feeling seems to be worse when ...

I have a 2002 S80 with 200kms. Late last year I started to develop a shimmy that was mostly felt in the rear end of the car at speeds of 80-110km. The shimmy is especially noticeable when accelerating and when the car settles down after going over a dip/rise in the highway. I live in MTL, Canada whe...