I had my wheels balanced with the Hunter GSP 9700 resulting in no more shimmy. Thanks to one and all for your comments and advice. The mechanic said that one wheel was off 1/4 oz. and that a second wheel was off 1/2 oz. - not a big deal according to him. However, the slight adjustment made the difference. By the way, the 18 x 8 front and 18 x 9.5 rear wheels with Yokohama AVS Sport tires at 235/50ZR-18 front and 255/45ZR-18 rear are working out well. The ride is really quiet.