Unplugged Performance requires 21 inch wheel setting when you install their lowering brackets. I have no idea why, but it must do something!
PLEASE NOTE: For use with Model S vehicles factory-equipped with air suspension only. To install on your Model S, you must have the 21″ wheel / tire calibration (if your vehicle was factory equipped with the 21″ Turbine wheels, this is by default). For vehicles that were originally equipped with wheels other than the factory 21″ Turbine option, the factory firmware can be recalibrated by a Tesla Service Center upon request. You are not required to utilize 21″ wheels with this product, but regardless of wheel / tire choice, the 21″ firmware calibration is required.