New brakes, new tire = equal vibration

[ttgxc]

I recently just had my winter wheels w/tires mounted on my car. At the same time I had the rear brake rotors and pads replaced. I had one of the tires replaced with a new one from tirerack due to a bulge in the sidewall. It is mounted and now on the front. The rest of the tires only have a few thousand miles. I had them all balanced and when I got the car back it was shaking pretty hard between 45-55mph and a little less at higher speeds. Also there was sometimes a vibration braking through that 45-55mph speed. I took it to another place to have the wheels road force balanced. Again I got it back, there was a large improvement, but still noticeable vibration at 45-55mph and a slight vibration that I could feel in the seat of my pants at highway speeds, but no more vibration while braking. Last year when I had these winter wheels and tires on, I had no problems and I had no problems with my summer wheels just before all this was done.

I am not sure how to address the issue. Is it the new tire? Is it where each wheel is mounted or is it even the new rear brakes? It is really annoying and I hate spending money twice already to have them balanced, but have a problem still there.