1. What is a Tyre and Wheel Size Calculator?

Definition: This calculator determines the overall diameter of a tyre based on the wheel diameter and sidewall height.

Purpose: It helps automotive professionals and enthusiasts calculate tyre dimensions for proper fitment and performance.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Diameter \) — Total tyre diameter (mm)
• \( wheel \) — Wheel diameter (mm)
• \( sidewall \) — Tyre sidewall height (mm)

Explanation: The wheel diameter is added to twice the sidewall height (since sidewall exists on both sides of the wheel) to get the total diameter.

3. Importance of Tyre Diameter Calculation

Details: Proper tyre diameter calculation ensures correct fitment, maintains speedometer accuracy, and affects vehicle handling characteristics.

4. Using the Calculator

Tips: Enter the wheel diameter in millimeters and the sidewall height in millimeters. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Where can I find the wheel diameter?
A: Wheel diameter is typically stamped on the wheel itself and is part of the tyre size marking (e.g., in "205/55R16", 16 is the wheel diameter in inches).

Q2: How do I determine sidewall height?
A: Sidewall height is calculated as (tyre width × aspect ratio). For example, a 205/55 tyre has sidewall height of 205mm × 0.55 = 112.75mm.

Q3: Why is tyre diameter important?
A: It affects clearance, gearing, speedometer accuracy, and overall vehicle dynamics. Different diameters may require suspension modifications.

Q4: Can I use inches instead of millimeters?
A: Yes, but ensure all measurements use the same unit. Multiply inches by 25.4 to convert to millimeters.

Q5: What's a typical wheel diameter range?
A: Passenger cars typically range from 14-20 inches (355-508mm), while trucks may go up to 24 inches (610mm) or more.