1. What is a Tyre Diameter Calculator?

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

Purpose: It helps vehicle owners, mechanics, and tyre professionals determine the correct tyre size for their vehicles.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Diameter \) — Overall tyre diameter (mm)
• \( Rim \) — Rim diameter (mm)
• \( Width \) — Tyre width (mm)
• \( Aspect \) — Aspect ratio (sidewall height as % of width)

Explanation: The formula calculates the total diameter by adding the rim diameter to twice the sidewall height (which is width multiplied by aspect ratio percentage).

3. Importance of Tyre Diameter Calculation

Details: Correct tyre diameter ensures proper speedometer accuracy, maintains vehicle handling characteristics, and prevents clearance issues.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Where can I find these tyre measurements?
A: They are printed on the tyre sidewall in the format: Width/AspectRatio Rim (e.g., 205/55 R16).

Q2: Why is tyre diameter important?
A: It affects speedometer accuracy, gearing, and can impact vehicle clearance and handling.

Q3: How much can tyre diameter vary?
A: Generally, you should stay within ±3% of the original tyre diameter when changing sizes.

Q4: Does this work for all tyre types?
A: Yes, the formula applies to standard radial tyres. Some specialty tyres may have different construction.

Q5: How do I convert the diameter to inches?
A: Divide the mm result by 25.4 to get diameter in inches.