Thanks for everyones input. To give a quick update on the issue. I went back to the tire shop (Mavis) and had them rebalance the two rear tires to no avail. We checked the rims and all agreed they looked fine. Here's the the tuff part. The two rear tires look to have a slight hop in them, these are the Pirelli Ice and snows, Im using the same size on the back as the front , which I was told by Tirerack and x5 board folk that it was ok. I also took the x5 to my local BMW shop where they checked the balance (regular and road force balanced) and found the wheels to be properly balanced. Funny the techs all thought the wheels were factory (cudos to Eurotech) and they found no issues with them. Next logical step is to replace the rear tires. Not sure how many people have had bad tires out of the box but I know its pretty rare. Still wondering if strechting the 275's on the rear rim is causing the issue. Feel like the tire has flatspots.

Thanks in again for your help,

jg