Well, my experience has been the following: On my 94 ATX I replaced all the tires, and all but 1 rim with ones from a 60K SHO.... Well, that one rim had a bend in it, on the inside that I did not see, so it shook and shimmied a bit at low and high speeds... My current 95 MTX has a bit of a shake at around 70-75, but anywhere after 80, its smooth sailing, so before I was thinking it was my rim(s) in front, but I ruined 2 of em last week, and now have tbird ones on the front, still a slight shake. however, I think a good balance is in order regardless, and I did have a weight fall off of my 17, which had effected that one... Sorry for the long rant, but I hope you get yours fixed, but first off, i woudl have a shop check the balance, and go from there.. GOOD LUCK!
Kevin