Have you checked your wheels to make sure the balancing weights are still there on both the inboard and outboard sides? Usually when one is thrown you'll see where it had been from lack of cleanliness and possibly corrosion.
I wouldn't think so either, until I got new tires put on last year. Drove the car away from the shop, all felt nice and smooth until I hit 60 mph where the vibration became so violent that the dash was rattling and probably about 2 minutes away from falling off. Returned the vehicle to the place only to find out that the balancing machine had reported the technicial to put 3 times the necessary balancing weight in the wrong place. So 1/3 the weight later at about 30 degrees different placment on the rim and I was back in business. So my point is throwing the balance off could result in different vibrations at different speeds. Even 8 months and a hellish winter later I went back due to wheel vibration and the balance was off again, the weight amounts and their placment had to be redone. So, though it might not completely solve your problem, if your balance hasn't been done in a while it's probably worth the money to go and get it done, I guarantee that the weights will be in different locations once it's been done and hopefully your vibration will be solved. In the sceme of it all this would probably be the cheapest method of crossing a possible culprit off the list.Grover said:But if it were a balance issue and the balance is that far off, I shouldn't have any smooth driving, should I?