I assume the speedometer is calibrated based on wheel rotation. Is it based on the front axle? (makes sense since they won't slip) Does anyone know how to re-calibrate the car if you get different size tires on the speed-measured-axle (I guess Tesla would be the place to go)? Has anyone attempted to do this yet? Down the road I may consider different wheels (currently have the standard 19's), and was wondering what effect it will have on the speedometer.