1. What is a Wheel Tyre Size Calculator?

Definition: This calculator determines the overall diameter of a wheel and tyre combination based on tyre width, aspect ratio, and rim diameter.

Purpose: It helps vehicle owners, mechanics, and enthusiasts determine proper tyre sizing for their vehicles and check clearance requirements.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( D \) — Overall diameter (inches)
• \( W \) — Tyre width (millimeters)
• \( AR \) — Aspect ratio (percentage)
• \( R \) — Rim diameter (inches)

Explanation: The formula converts the sidewall height from millimeters to inches (hence the 25.4 conversion factor) and accounts for both sidewalls (top and bottom) plus the rim diameter.

3. Importance of Tyre Size Calculation

Details: Proper tyre sizing ensures accurate speedometer readings, maintains vehicle handling characteristics, and prevents clearance issues with wheel wells or suspension components.

4. Using the Calculator

Tips: Enter the tyre width in mm (e.g., 225), aspect ratio (e.g., 65 for 65%), and rim diameter in inches (e.g., 16). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Where can I find my current tyre size?
A: Look on the sidewall of your tyre - it will be in the format like "225/65R16" where 225 is width, 65 is aspect ratio, and 16 is rim diameter.

Q2: Why is overall diameter important?
A: Changing the overall diameter affects speedometer accuracy, gear ratios, and may cause clearance issues.

Q3: What's a typical aspect ratio?
A: Common aspect ratios range from 30 (low profile) to 75 (high profile), with 50-65 being typical for most passenger vehicles.

Q4: How much can I change my tyre diameter?
A: Generally, staying within ±3% of the original diameter is recommended to avoid significant issues.

Q5: Does this calculator work for plus-sizing wheels?
A: Yes, you can use it to compare different wheel/tyre combinations while maintaining similar overall diameters.