the heavier the wheel/tire the harder it is to shake the shimmey, 15s and 16s are fairly easy to get to run true but bigger then that and the weight is harder to control, stiff thick sidewalls and bigger rims gets the mass farther from the hub, and that shows the flaw in the suspension design, if you think a e34 shimmeys you outta check out a e38 with 19"s, you'd think the car was coming off the ground