Changing your vehicle’s wheels and tires can significantly enhance its look and performance. However, upgrading to a different tire size requires recalibrating your vehicle’s computer to ensure accurate speedometer readings and proper system functions. This is where a Cable Connection Scan Tool and software like AlfaOBD come into play, especially for FCA group vehicles (Chrysler, Dodge, Ram, Jeep, Fiat, Alfa Romeo). This guide walks you through the process of using these tools to adjust your tire size, drawing from a real-world experience with a 2021 Ram Laramie.
Essential Tools for Tire Size Adjustment
To begin, you’ll need a few key components:
- AlfaOBD Software: This powerful diagnostic software allows for in-depth customization and diagnostics of FCA vehicles. It’s available for both PC and Android platforms. You can find it at https://alfaobd.com/.
- OBDLink MX+ Scan Tool: A reliable OBD adapter is crucial for establishing communication between your vehicle and the AlfaOBD software. The OBDLink MX+ is a recommended option known for its compatibility and performance.
- Security Bypass Cable: For newer FCA vehicles, accessing certain modules requires bypassing the security gateway. A cable connection scan tool adapter, such as the one from Amazon (https://www.amazon.com/Bosting-Adaptor-Chrysler-Programming-Connector/dp/B07S91VZXT/ref=sr_1_5?crid=PWO801WVQS19&dchild=1&keywords=chrysler+12+8+cable&qid=1635258116&sprefix=chrysler+12,aps,144&sr=8-5), is necessary to bypass this security and allow modifications.
Setting Up the Connection and Software
- Install AlfaOBD: Download and install AlfaOBD on your laptop or Android device. The licensing process is straightforward and typically takes just a few minutes.
- Connect the Security Bypass Cable: Locate the OBD connectors behind the driver’s side knee bolster. Disconnect the factory connectors and plug them into the “Y” adapter cable. This bypasses the security module, allowing AlfaOBD to communicate with protected systems.
- Connect OBDLink MX+: Plug the OBDLink MX+ scan tool into the OBD end of the bypass cable.
- Establish Connection with AlfaOBD: Launch AlfaOBD and establish a connection to your vehicle using the OBDLink MX+. For mobile devices, ensure Bluetooth is enabled and paired with the OBDLink MX+.
Adjusting Tire Size in AlfaOBD
Once connected, navigate through the AlfaOBD interface to locate the tire size adjustment settings. A helpful video guide, such as the one mentioned in the original article, can be invaluable for this process. Here are the general steps:
- Access ABS Module: In AlfaOBD, connect to the ABS (Anti-lock Braking System) module of your vehicle.
- Navigate to Tire Configuration: Look for options related to “tire configuration,” “tire size,” or “rolling circumference.”
- Input New Tire Size: Calculate or find the revolutions per mile for your new tires. Alternatively, you can input the tire diameter or rolling circumference in millimeters. For example, using the revolutions per mile (e.g., 611 revs/mile), calculate the millimeters per revolution:
(5280 feet/mile * 12 inches/foot * 25.4 mm/inch) / 611 revs/mile. - Apply Changes: Input the calculated value into AlfaOBD and apply the changes.
- Verify Speedometer Accuracy: After adjustment, test drive your vehicle and compare the speedometer reading with a GPS-based speed app like Waze to ensure accuracy.
Final Thoughts and Tips
Using a cable connection scan tool with AlfaOBD simplifies modifications like tire size adjustments on modern FCA vehicles. Leaving the bypass cable connected and tucked away for future use can save time if you anticipate further modifications. This process, while requiring specific tools, is ultimately less complex than it might initially seem, offering a DIY solution to ensure your vehicle’s systems are correctly calibrated after tire upgrades. Remember to always double-check your connections and settings, and consult reliable resources for guidance throughout the process.
