Tire Circumference Calculator
Calculate tire circumference, revolutions per mile, and speedometer error when changing tire sizes. Essential for tuning, gear ratios, and accurate speed readings.
Step 1: Original Tire Size
Understanding Tire Sizes
Tire size is typically written as 225/45R17 – where 225 is width in mm, 45 is aspect ratio (height as % of width), and 17 is wheel diameter in inches.
Step 2: New Tire Size & Comparison
Why Circumference Matters
Tire circumference affects speedometer accuracy, odometer readings, gear ratios, and vehicle performance. Larger tires cover more ground per revolution.
Tire Calculation Results
Tire Circumference
Tire Size Comparison
| Measurement | Original Tire | New Tire | Difference |
|---|
Speedometer Impact
When your speedometer reads 60 mph, your actual speed will be 60 mph (0.0% difference).
Technical Specifications
Tire Circumference Formula
Circumference = π × Diameter
Diameter = (Tire Width × Aspect Ratio ÷ 100 × 2) ÷ 25.4 + Wheel Diameter
Where: Tire width in mm, Aspect ratio as percentage, Wheel diameter in inches, 25.4 mm per inch.
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