The Superchips Tirepaq Speedometer Calibrator Programmer electronically corrects the vehicle’s speedometer to compensate for non-stock tires, wheels and rear-end gear swaps. Works with tires between 26″ and 36″ as well as 3:42, 3:73, 4:10, 4:56 and 4:88 gear ratios. Superchips Tirepaq Speedometer Calibrator Programmer also intelligently adjusts shift patterns to improve driveabiltiy when aftermarket tires, wheels and gears are installed. Superchips Tirepaq Speedometer Calibrator Programmer can be easily upgraded to a full featured Flashpaq Performance Programmer via the internet for an additional charge!