Took my 20" wheels and tires for balancing to a shop with the Hunter Road Force touch. This is the current state of the art for wheel and tire balancing. The machine exerts a force on the tire as the wheel spins and indicates on a monitor the out-of-balance points on both the wheel and tire. It provides a "road force" rating number. If the rating is above a specified limit the tire has to be loosened on the rim and turned so that the out-of-blance points are opposite each other. Once that's done the service tech follows steps to fine tune the balance of the wheel/tire assembly. The process took about an hour and cost about $60 total for all four wheel/tire assemblies. What a change it made! My Model S was as smooth on the road as it has ever been and much smoother than with any conventional balancing I've had done before (at least twice a year). I highly recommend that when fellow owners need to balance their wheels that they do it only at a shop with the Road Force Touch. Thanks to Xenoilphobe for recommending this system in the carbon fiber rim thread.