1. What is a Tire Size Calculator?

Definition: This calculator estimates vehicle speed based on tire revolutions per minute (RPM) and tire diameter.

Purpose: It helps automotive professionals and enthusiasts determine vehicle speed for different tire sizes and RPM combinations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (miles per hour)
• \( RPM \) — Revolutions per minute
• \( \pi \) — Pi (approximately 3.14159)
• \( TD \) — Tire diameter (inches)
• 1056 — Conversion factor (combines unit conversions for mph)

Explanation: The formula calculates how much distance the vehicle travels per minute based on tire rotation, then converts to miles per hour.

3. Importance of Tire Size Calculations

Details: Proper tire size calculations ensure accurate speedometer readings, proper gearing, and optimal vehicle performance.

4. Using the Calculator

Tips: Enter the RPM (typically from 500-3000 for normal driving) and tire diameter in inches. All values must be > 0.

5. Frequently Asked Questions (FAQ)

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

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

Q3: Does this work for any vehicle?
A: Yes, as long as you have accurate RPM and tire diameter measurements.

Q4: How does tire wear affect the calculation?
A: Worn tires have slightly smaller diameter, which would result in slightly lower actual speed than calculated.

Q5: Can I use this for speedometer calibration?
A: Yes, this helps determine actual speed when changing tire sizes from factory specifications.