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Tire Diameter Formula:
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The Alloy Wheel Size Calculator calculates the overall tire diameter from wheel size and sidewall height. This measurement is crucial for proper vehicle fitment, speedometer accuracy, and performance optimization.
The calculator uses the tire diameter formula:
Where:
Explanation: The formula accounts for both the wheel diameter and the additional height contributed by the tire on both sides of the wheel.
Details: Accurate tire diameter calculation is essential for maintaining proper vehicle clearance, ensuring speedometer accuracy, optimizing performance, and preventing rubbing issues with wheel wells and suspension components.
Tips: Enter wheel diameter and sidewall height in inches. Both values must be positive numbers. Common wheel diameters range from 15-22 inches for passenger vehicles.
Q1: Why is overall tire diameter important?
A: Overall diameter affects speedometer accuracy, gear ratios, clearance, and vehicle performance. Significant changes can impact these systems.
Q2: How do I find sidewall height?
A: Sidewall height can be calculated from tire size markings (e.g., 225/45R17: 225mm width × 45% aspect ratio = sidewall height).
Q3: What's the maximum diameter change allowed?
A: Generally, stay within ±3% of original diameter to maintain proper vehicle function and avoid clearance issues.
Q4: Does wheel width affect diameter calculation?
A: Wheel width doesn't directly affect diameter calculation but can influence tire profile and actual mounted dimensions.
Q5: Can I use this for plus-sizing wheels?
A: Yes, this calculator helps maintain proper overall diameter when changing wheel sizes while adjusting tire profiles accordingly.