Hypertech Speedometer Calibrator
If you have changed the tire size or gear ratio in any OBD II vehicle, this unit is a must. I went from 32" to 35" tires. My speedometer, odometer, and MPG computer were off quite a bit. This unit is incredibly easy to use. Find your OBD port, plug it in and follow the instructions presented to you on the screen. You're done in a few minutes, and your vehicles computer has been re-programmed for the proper tire size and gear ratio.