How to Correct Your Speedometer for Accurate Readings – Hypertech, Inc.

How to Correct Your Speedometer for Accurate Readings

If your vehicle has larger than stock tires and/or a rear gear ratio that did NOT come from the factory for normal speedometer calculations, you might need to recalibrate the speedometer on your vehicle to keep it compliant with the law and keep you safe while driving.


Understanding Speedometer Calibrators

A Speedometer Calibrator is a tool used for correcting a vehicle’s speedometer accuracy. It is typically used after installation of a larger than stock tire size OR a different rear gear ratio. The speedometer calibrator adjusts the vehicle's onboard computer so that the speedometer displays an accurate speed. This adjustment ensures the vehicle maintains legal compliance and keeps it safe on the road. Inaccurate speedometers can increase the chances of a ticket or an accident.


Why Correct Your Speedometer?

Correcting your speedometer reading is important for both legal compliance and driving safety. Accurate speed readings help you avoid traffic violations and make accidents less likely, as you can keep your vehicle in the correct speed range given the road and traffic conditions. An incorrect speedometer reading can also alter mileage on the odometer, which affects maintenance schedules and could mislead prospective buyers during a resale, potentially causing legal headaches.


The In-Line Speedometer Calibrator® Module

The In-Line Speedometer Calibrator Module is the ideal solution for vehicles whose onboard computers do not allow easy adjustments based on tire size or rear gear ratio changes. It also works well for vehicles with an installed tire size/rear gear ratio that is  beyond the range of standard programmers.


This module integrates with the vehicle’s system via a simple USB connection to a PC, where you can input the new tire height and/or gear ratio. To install it, you must disconnect the factory connector to the instrument cluster, plug in the module and then reconnect the instrument cluster. It's a quick setup process that most vehicle owners are able to do on their own.


The Installation Process

Installing the In-Line Speedometer Calibrator Module is a straightforward procedure that can be completed quickly, making your vehicle's speedometer read accurately in just minutes. Begin by connecting the module to a PC using the provided USB cable. This connection allows you to access the software you need to input the new tire height or rear gear ratio. Once you've updated these settings, the module will be ready for installation in the vehicle.


Next, locate the factory connector to the instrument cluster, which is typically positioned behind the instrument cluster. Disconnect this connector -- be careful not to inadvertently pull any other wires -- and plug in the In-Line Speedometer Calibrator Module. Make sure the connection is secure and then reconnect the factory instrument cluster connector to the module. This setup forms a pass-through that allows all vehicle data to pass through the new calibrator.


Once everything is connected, it's a good idea to conduct a final check to be sure the system recognizes the new settings and the speedometer is reading accurately.