1. What is Tire Diameter?

Tire diameter is the overall height of the tire when mounted and inflated, measured from the bottom of the tire to the top through the exact center. It's a crucial measurement for vehicle fitment and performance.

2. How Does the Calculator Work?

The calculator uses the tire diameter formula:

Where:

• \( Rim \) — Wheel rim diameter in inches
• \( Sidewall \) — Tire sidewall height in inches

Explanation: The total diameter includes the rim diameter plus the sidewall height at both the top and bottom of the wheel.

3. Importance of Correct Tire Diameter

Details: Proper tire diameter ensures correct speedometer readings, maintains vehicle clearance, and affects gear ratios. Significant diameter changes can impact ABS systems and vehicle dynamics.

4. Using the Calculator

Tips: Enter rim diameter and sidewall height in inches. Both values must be positive numbers. The sidewall height is often found in the tire size marking (e.g., in "225/45R17", 45 is the aspect ratio which can be converted to sidewall height).

5. Frequently Asked Questions (FAQ)

Q1: How do I find my sidewall height?
A: For a tire marked "225/45R17", the sidewall height is 225mm × 45% = 101.25mm, which converts to about 3.99 inches.

Q2: What's the acceptable diameter difference?
A: Generally, keep within 3% of original diameter to avoid speedometer errors and other issues.

Q3: Does diameter affect performance?
A: Larger diameters may improve handling but can reduce acceleration. Smaller diameters may improve acceleration but reduce top speed.

Q4: How does diameter affect speedometer readings?
A: Larger tires make the speedometer read slower than actual speed, while smaller tires make it read faster.

Q5: Can I use this for plus-sizing calculations?
A: Yes, this helps maintain overall diameter when changing wheel sizes while adjusting tire profile.