It is likely the BFG's that come stock on the car. These tires get out of round just sitting in the garage over night. For the first 4-5 miles every morning it is like driving a truck until they get warmed up. Between that and the timing advance until the engine gets warm, it is not my favorite ride.
Additionally, like others have said, for some reason these wheels throw weights which makes them out of balance.
>>> I see this as a good reason to burn off a little rubber and get a real set of tires.