Have you watched them balance the wheels? If not, make sure they take ALL the weights off, spin the wheel, place the weights, and
re-spin the wheel. A lot of places don't bother to re-sping the wheel.
I've balanced wheels before (long ago...but I've done it), and I've placed the weights slightly off, which translates to a big vibration.
So, make sure they're doing it right.
Also, any respectable place will rebalance if they didn't get it right the first time.
Good luck!
