Modern machines just use targets & infrared or lasers, they only do compensation with a roll-out method, they have to be mounted vertically then rolled so far & held, then back to vertical. The clamping fixtures hit the quarters. The old ones got jacked up by the body, & got a 2 or 3-point compensation spinning the wheel 360°, but once done You could position the wheel & clamp fore&aft so You were clear of the wheel lip. But even those with a tight Sure-Grip, You had to be sure to place both fixtures so they'd be horizontal together.