Thanks for the input. I've been chasing one vibration or another since new and I've spent a ridiculous amount if time trying to resolve it. Let me add, the new tires resolved any front end vibrations I was having with the Forteras. The front end is planted and no shimmy at any speed even while the vibration is present. Alignment was done three weeks ago.
Leads me to believe its a problem in the rear? I wondered about warped rotors too. Anything else that can oscillate under there?? Exhaust?? Is it reasonable to just road force the rears? I know one shop I contacted only offered the service for all four wheels which I found odd.
Before the vibration sets in the drive quality is fantastic but once it creeps in, it's there for the duration of the drive.