Coding
Tire Size Recalibration
Price
$45
starting price · see note below
Duration
20–40 min
at your location
Booking
Bigger tires changed your vehicle's rolling circumference, so the speedometer, the odometer and the speed-based logic are all off by the same percentage. On supported vehicles the correct tire size is written into the vehicle's own configuration through the OBD port — a coding change with no hardware, no calibrator box and nothing to wire in. RAM and Jeep through AlfaOBD, Ford through FORScan, European vehicles through the correct software for their systems. Compatibility varies by year, make and model, and the module the setting lives in differs between platforms — I verify yours before you spend anything.
Tire size changes your vehicle's rolling circumference — how far it travels for one full turn of the wheel — and it calculates speed from wheel-speed data configured for the tires it left the factory with. Bigger tires therefore throw the speedometer and the odometer off by the same percentage.
The fix is a configuration change, not hardware: on supported vehicles the correct tire size is written into the vehicle's own configuration through the OBD port. RAM and Jeep through AlfaOBD, Ford through FORScan, European vehicles through the correct software for their systems — then verified while I'm standing at the vehicle.
What this addresses
- You fitted bigger tires and the speedometer now reads low
- Shift points or other speed-based behaviour feel wrong after a lift
- You changed wheel or tire size and want the vehicle configured correctly
- A tire-size question after a wheel change — including whether other modules need it too
Compatibility
Supported years and procedures vary by year, make and model — some vehicles accept the tire-size configuration through their modules, others don't, and the module it lives in differs between platforms. I verify yours before booking. This is a coding and configuration change only: no hardware is fitted and no mechanical work is done.
How mobile service works
- 1Tell me your year, make, model, engine — and what your car is doing (or what feature you want changed).
- 2I verify your vehicle and confirm the service is supported before you spend anything — compatibility varies by year, make and model.
- 3I confirm the price with you before I head out. Prices are starting prices; a travel fee applies beyond 10 miles.
- 4I come to you — your home, your office, your driveway. No waiting room, no dealership lane.
- 5I work with professional equipment, explain what I find in plain English, and deliver — a diagnostic report, a reset, a feature unlocked.
Common questions
Which module gets changed?
It differs between platforms — on some vehicles the cluster carries it, on others the body or other modules need it too. I confirm where it lives on your vehicle before we schedule.
Will this fix my speedometer exactly?
On supported vehicles the correct tire size is written in, so the speed calculation follows the tires you're running rather than the factory size. I verify it on-site rather than telling you it's done and driving off.
Do you fit anything to the vehicle?
No — no module to swap, no calibrator to wire in, nothing zip-tied under the dash. It's a configuration value written through the OBD port.
Go deeper
Tire size & speedometer recalibration
A lift and bigger tires changed your rolling circumference — so the speedometer reads low and the shift points are off. It's a configuration change, not hardware. $45.
Read the full guideReady when you are
Send your year, make, model and what you need done. I verify compatibility before you book.
Serving Chattanooga and surrounding areas — I come to you. Enter your ZIP to confirm coverage.
Prices are starting prices, not guarantees. Final pricing can depend on vehicle, location, diagnostic complexity and requested procedure. This is an electronic diagnostics, coding and reset service — not mechanical repair. Diagnostics identify electronic faults but do not guarantee that a specific mechanical repair will resolve a problem. No dealership or manufacturer affiliation.