Correcting Speedometer After Tire Size Change Using Bluedriver OBD2 Scanner

Changing your vehicle’s tire size can offer numerous benefits, from enhancing its appearance to improving off-road performance. However, a common issue that arises after such modifications is an inaccurate speedometer. When you deviate from the stock tire size, your speedometer and odometer readings can be thrown off, leading to incorrect speed readings and mileage tracking. This is where an OBD2 scanner, like the Bluedriver, comes in handy, allowing you to recalibrate your system for accurate measurements.

For example, consider upgrading your Jeep Patriot’s tires. If you’ve moved from a stock size like 215/60/R17 to a larger all-terrain tire such as 225/65/R17, you might notice your speedometer reading lower than your actual speed. Many enthusiasts who install larger, more aggressive tires face this issue, as wider and taller tires alter the rolling circumference, which is what the vehicle’s computer uses to calculate speed.

Alt: Bluedriver OBD2 scanner plugged into the diagnostic port of a Jeep Patriot, ready for tire size recalibration.

The problem with an inaccurate speedometer goes beyond just knowing your speed. It affects your odometer, potentially underreporting mileage, and can even impact systems that rely on accurate speed data, like your vehicle’s stability control. Fortunately, you can rectify this issue yourself using an OBD2 scanner and a smartphone app.

Why Tire Size Affects Speedometer Accuracy

Vehicle speedometers are calibrated at the factory to work with the stock tire size. They calculate speed based on the rotations of your tires. When you change tire sizes, especially the diameter, the number of rotations per mile changes. Larger diameter tires cover more distance per rotation than smaller ones. Consequently, if you install larger tires without recalibrating, your speedometer will read slower than your actual speed, and your odometer will record fewer miles than you’ve actually traveled.

Using an OBD2 Scanner for Tire Size Adjustment

An OBD2 scanner, particularly when paired with a capable app, provides a straightforward solution to correct your speedometer after a tire size change. While the original article mentioned JScan app, for broader audience appeal and keyword relevance, we’ll discuss how similar functionalities can be achieved with tools like Bluedriver OBD2 scanner, which is a popular choice among car enthusiasts. Although specific tire size adjustment features might vary between OBD2 scanners and apps, the general principle remains the same. You’re essentially accessing your vehicle’s computer (ECU or PCM) to tell it the new tire size, so it can recalculate speed and distance accurately.

Tools You’ll Need

To recalibrate your speedometer, you will generally need:

1. An OBD2 Scanner: A reliable OBD2 scanner is crucial. While the original article mentions Veepeak and Vgate, Bluedriver is another excellent option known for its user-friendliness and comprehensive features. Ensure the scanner you choose is compatible with your vehicle and supports advanced functions like configuration changes.
2. A Compatible Smartphone or Tablet: Most OBD2 scanners connect to your smartphone or tablet via Bluetooth. You’ll need a device compatible with the scanner’s app.
3. An App for OBD2 Scanner: You’ll need to download the app designed to work with your chosen OBD2 scanner. For Bluedriver, this would be the Bluedriver app. Other scanners may use apps like Torque Pro, Carista, or OBDLink, depending on compatibility and features. These apps often provide the interface to access vehicle settings.
4. A Tape Measure: While online tire size calculators can give you a theoretical diameter, measuring your tire’s actual diameter is more accurate.

Step-by-Step Guide to Recalibrate Your Speedometer (General Steps)

Keep in mind that the exact steps might vary based on your specific OBD2 scanner and app. Consult your scanner’s manual and app instructions for the most accurate process. However, here are general steps you can expect to follow:

1. Connect the OBD2 Scanner: Locate the OBD2 port in your vehicle (typically under the dashboard on the driver’s side). Plug in your Bluedriver or chosen OBD2 scanner.
2. Pair with Your Smartphone/Tablet: Turn on your vehicle’s ignition (you don’t need to start the engine in most cases, but sometimes the engine needs to be running). Enable Bluetooth on your smartphone or tablet and pair it with the OBD2 scanner, usually through the scanner’s app.
3. Launch the OBD2 Scanner App: Open the app associated with your OBD2 scanner (e.g., Bluedriver app). Allow the app to connect to the scanner and your vehicle’s computer.
4. Navigate to Vehicle Settings or Configuration: Within the app, look for sections like “Settings,” “Configuration,” “Vehicle Settings,” “PCM Configuration,” or similar terms. The location of tire size settings can vary.
5. Find Tire Size or Tire Diameter Setting: Once in the settings menu, search for options related to “Tire Size,” “Tire Diameter,” “Wheel Size,” or “Speedometer Calibration.”
6. Measure Your Tire Diameter: Use a tape measure to get the most accurate measurement of your tire’s diameter. Measure from the top to the bottom of the tire when it’s mounted on your vehicle and properly inflated. Compare this measurement to online tire size calculators to verify. Input this measured diameter in inches into the app.
7. Enter the New Tire Size: In the app, you may be prompted to enter the new tire size in various formats (diameter in inches, tire code, etc.). Use the measured diameter or the calculated diameter based on your tire size (e.g., 225/65/R17) if the app requires it.
8. Apply or Save Changes: After entering the new tire size, there will typically be an option to “Apply,” “Save,” or “Write Configuration.” Select this option and wait for the app and scanner to communicate with your vehicle’s computer and update the settings. Be patient during this process; it may take a few minutes.
9. Verify Speedometer Accuracy: After the changes are applied, test your speedometer. Use a GPS app on your phone or a GPS-enabled device to compare your actual speed with your speedometer reading at different speeds. Fine-tune the tire size setting in the app if needed for optimal accuracy.

Alt: Screenshot of the JScan app interface showing options for tire size adjustment, illustrating the type of software used with OBD2 scanners for recalibration.

Choosing the Right OBD2 Scanner

When selecting an OBD2 scanner for tire size correction and other vehicle diagnostics, consider the following:

• Compatibility: Ensure the scanner is compatible with your vehicle’s make and model, specifically for advanced functions like configuration changes. Some scanners are brand-specific or have limited compatibility.
• Features: Not all OBD2 scanners offer tire size recalibration. Check the scanner’s features and app capabilities to confirm it supports this function. Bluedriver and similar advanced scanners often provide this level of control. Basic scanners may only offer diagnostic code reading and clearing.
• User-Friendliness: Opt for a scanner and app that are user-friendly, with clear instructions and an intuitive interface.
• Reviews and Recommendations: Read reviews and seek recommendations from other car owners or online forums to find reliable and effective OBD2 scanners.

Important Considerations and Troubleshooting

• Connection Issues: As mentioned in the original article, you might encounter connection issues between the OBD2 scanner and your smartphone or the vehicle. Ensure Bluetooth is enabled, the app is correctly configured, and try restarting the app or reconnecting the scanner if needed. Sometimes, turning the vehicle’s ignition off and on again can help.
• App Stability: Wait patiently for the app to process changes. Do not interrupt the process or close the app prematurely, as this could lead to errors.
• Double-Check Settings: Before making changes, note down your original tire size settings in the app, if possible. This allows you to revert to the original settings if needed.
• Caution: Be cautious when changing settings using an OBD2 scanner. Only modify settings you understand, and avoid making random changes, as this could potentially affect your vehicle’s systems. If unsure, consult your vehicle’s repair manual or seek professional advice.

Correcting your speedometer after changing tire sizes with an OBD2 scanner like Bluedriver is a manageable DIY task for most car owners. It ensures accurate speed and mileage readings, maintaining the integrity of your vehicle’s systems. By following the steps outlined and choosing the right tools, you can easily adapt your vehicle’s computer to your new tire specifications and enjoy the benefits of your tire upgrade without compromising accuracy.