1. What is a Tire Size Speed Calculator?

Definition: This calculator estimates vehicle speed in miles per hour based on engine RPM and tire diameter.

Purpose: It helps automotive enthusiasts, mechanics, and engineers understand the relationship between engine speed and vehicle speed for different tire sizes.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (miles per hour)
• \( RPM \) — Engine revolutions per minute
• \( \pi \) — Mathematical constant Pi (~3.14159)
• \( TD \) — Tire diameter (inches)
• 1056 — Conversion factor (combines unit conversions for mph)

Explanation: The formula calculates how much distance the vehicle covers per minute based on tire circumference and RPM, then converts to miles per hour.

3. Importance of Speed Calculation

Details: Understanding this relationship is crucial for gear ratio selection, transmission tuning, and verifying speedometer accuracy with non-standard tire sizes.

4. Using the Calculator

Tips: Enter the engine RPM and tire diameter in inches. The tire diameter should be the overall height of the mounted, inflated tire.

5. Frequently Asked Questions (FAQ)

Q1: How do I measure tire diameter?
A: Measure from the ground to the top of the tire when properly inflated, or calculate from tire size markings (e.g., 225/45R17).

Q2: Why is the conversion factor 1056?
A: It combines conversions from inches to miles (63360) and minutes to hours (60): 63360/60 = 1056.

Q3: Does this account for gear ratios?
A: No, this assumes direct 1:1 drive ratio. For accurate results, use RPM at the wheels (after all gear reductions).

Q4: How accurate is this calculation?
A: It provides theoretical speed. Actual speed may vary due to tire slip, inflation, and load.

Q5: Can I use this for metric measurements?
A: You would need to convert metric tire sizes to inches for this calculator.