Speedometer Calculator
Calculate your vehicle’s true speed and odometer error when changing tire sizes, wheel dimensions, or gear ratios. Adjust for speedometer inaccuracies and avoid speeding tickets.
Step 1: Original Setup
Understanding Tire Size
Tire diameter affects speedometer accuracy. Larger tires cover more ground per revolution, causing speedometer to read slower than actual speed. Smaller tires have the opposite effect.
Step 2: New Setup
About Speedometer Calibration
Speedometers are calibrated at the factory for specific tire sizes and gear ratios. Changing either component without recalibrating can result in inaccurate speed readings and incorrect odometer mileage.
Speedometer Calculation Results
Actual Vehicle Speed
Speed Comparison at Different Sizes
| Tire Size | Displayed Speed | Actual Speed | Difference | Error % |
|---|
Odometer Error Analysis
Odometer Error Formula
Error % = ((New Diameter ÷ Original Diameter) – 1) × 100
The odometer error is calculated by comparing the tire diameters. Actual distance = Displayed distance × (New Diameter ÷ Original Diameter). A positive error means you’re traveling farther than displayed.
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