front end vibration

My 98 Aurora has a persistent steering vibration/shimmy at between 60 and 75 mph. I have (repeatedly) balanced and rotated the wheels. I replaced the tires. It does not occur on braking so I don't think it is the rotors. The front end appears tight. Could it be worn front struts? Any other ideas?

Sounds like wheel balance. Do you get balanced static or dynamic ? Static = weights on inside only
Dynamic = weights on both sides. Dynamic is the better balance. Also how are they being balanced ? Do they mount it with the wheel center or with the stud holes? I prefer the stud hole method. Also does it vibrate on acceleration ?

Find a shop that has a Hunter road force balancer. It applies pressure with a roller against the tread while spinning it. This method has worked for many Aurora owners in eliminating the vibration.

Thanks for the responses. It doesnt vibrate noticeably on acceleration - I only notice it when I am on the highway at between about 60 and 75. I will try the Hunter road force approach and see if that helps.