...just a comment from my recent experience. It took me a long time to get the aftermarket 18's for my X-Type that I really wanted. They came with polycarbonate hub centering rings. After being Hunter Road Force balanced (twice to make sure), I bolted them on and got an awful shaking above 60 mph. Went back and re-torqued everything. No change. I figured out that the hub centering rings had a small flange that had to come off as there was a business card sliver of a gap between the wheel and hub. That made it better. But, it wasn't until I had a machine shop make me a set, using precise measurements, and pressing them into the wheels that the shimmy went away. The extra $120 was worth every penny. So, if you are going with aftermarket wheels, even though you think those hub centering rings don't make a big difference, experience dictates that they do. Get a precise set made if you really want to be happy.