I am assuming you have fuchs correct? I have found these wheels notoriously tough to throughly balance for all speeds with no detectable shimmy...you usually sacrifice a slight shimmy here or there. The wheels are so light usually the tire assembly takes control of the wheel.
First off, make sure they are not static balanced...all weights on the inside to hide them. This is ridiculous IMO that people sacrifice looks for imbalanced wheels/tires. You don't want this.
I am a wheel balance freak. I have found that the taller the sidewall of the tire the tougher it is to get a good balance. My fuchs on my 84 Carrera never really balanced up correctly. Moving to a 17's eliminates any balance problems since the sidewall is so small...no flexing at speed to throw the works off. Smooth as silk at all speeds.
High spots on the tire will not cause a shimmy...more of a hopping action which at speed just feels like a vibration. I am sure your suspension is fine...can't think of too many suspension realted issues to cause a shimmy except for the obvious...tug on things shake things, if it is really loose that may cause it, but probably just the tires, maybe a loose wheel bearing.
Some shops like Radial Tire can balance on the car as an assemby, you just need to index the wheels and put back if replaced, otherwise you have not felt anything like this type of vibration
I had them do this with my fuchs and was not impressed, the tech was in a hurry and did not take his time. It takes a long time to get this right.
I used to balance the wheels on my Honda CRX in college. No shop could ever get it right. Front drivers are great for this...just put it up on blocks and run it up to your problem area and start moving weight around and experiment with different sizes. You can really fine tune this and you would be surprised at how much wheel weight you do not really need to make a wheel run smoothly. I was doing this to within .005 grams of weight
Tire balancing is somewhat of an art form IMO for correctly balancing a wheel. 9 out of 10 tires jockies just read the machine and do what it tells them without using common sense. Also if tire jocky 1 has just balanced some SUV wheels that are 30 inch in diameter and weigh 50lbs. the machine should be recalibrated before the delicate fuchs are balanced.
I have a ton more info on this if you need it.
-Jeff Kramer
nolift911@hotmail.com