...The Sonic speed is read from the driver's side rear tire...
Stew,
Well that negates everything about the UG performance mode then. You could hit 60 standing still if you were on ice with the front wheels spinning. I could swear that I've never seen the speedo swing wildly if the front wheels are spinning. I guess the only way to get a real 60 number is with a 5th wheel attached to the vehicle that's independent of everything else.
Tony