1. What is a Car Tyre Size Calculator?

Definition: This calculator estimates the overall diameter of a car tyre based on rim diameter, tyre width, and aspect ratio.

Purpose: It helps car enthusiasts, mechanics, and drivers understand tyre dimensions for proper fitment and performance.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Diameter \) — Overall tyre diameter (millimeters)
• \( rim \) — Rim diameter (inches)
• \( width \) — Tyre width (millimeters)
• \( aspect \) — Aspect ratio (percentage of width)

Explanation: The rim diameter is converted to millimeters, then the sidewall height (calculated from width and aspect ratio) is added twice (for top and bottom).

3. Importance of Tyre Size Calculation

Details: Proper tyre diameter calculation ensures correct speedometer readings, proper clearance, and optimal vehicle performance.

4. Using the Calculator

Tips: Enter the rim diameter in inches, tyre width in millimeters, and aspect ratio as a percentage. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Where can I find my tyre size information?
A: It's printed on the tyre sidewall in the format like "205/55R16" where 205 is width, 55 is aspect ratio, and 16 is rim diameter.

Q2: Why convert rim diameter to millimeters?
A: The calculation combines imperial (inches) and metric (mm) measurements, so we convert everything to millimeters for consistency.

Q3: What does aspect ratio mean?
A: It's the height of the tyre's sidewall expressed as a percentage of the tyre's width.

Q4: How accurate is this calculation?
A: It provides a theoretical diameter - actual tyres may vary slightly due to manufacturing tolerances and tread depth.

Q5: Why is diameter important when changing tyres?
A: Significant diameter changes affect speedometer accuracy, ABS systems, and may cause clearance issues.