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Tire Size Calculator — Compare Diameter, Clearance & Speedometer Error
Editable live calculator
Change any input — the result updates immediately
No hidden assumptions. Inputs, units and the working stay visible so you can check the calculation.
Calculated result
+3.49% diameter change
Original: 31.61 in diameter · 99.29 in circumference
New: 32.71 in diameter · 102.76 in circumference
At an indicated 60, theoretical actual speed is 62.09 in the same speed unit.
Axle-center ground-clearance change: 0.55 in.
Show the working
- 1. Sidewall = width × aspect ratio ÷ 100 ÷ 25.4.
- 2. Overall diameter = rim + 2 × sidewall.
- 3. Speed ratio follows new diameter ÷ original diameter when calibration is unchanged.
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