1. What is 4250 RPM in MPH Calculator?

Definition: This calculator determines the vehicle speed in miles per hour (mph) at 4250 revolutions per minute (RPM) for different tire sizes.

Purpose: It helps automotive enthusiasts and mechanics understand the relationship between engine RPM and vehicle speed based on tire diameter.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (mph)
• \( 4250 \) — Constant RPM value
• \( TD \) — Tire diameter (inches)
• \( 336 \) — Conversion factor

Explanation: The formula converts rotational speed to linear speed by accounting for tire circumference and unit conversions.

3. Importance of RPM to MPH Calculation

Details: Understanding this relationship helps with gear ratio selection, performance tuning, and diagnosing transmission issues.

4. Using the Calculator

Tips: Enter the tire diameter in inches (measured from ground to top of tire). The diameter must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Where does the 336 constant come from?
A: It combines unit conversions (5280 ft/mile, 12 in/ft) and accounts for the relationship between RPM and mph.

Q2: How do I measure tire diameter accurately?
A: Measure from the ground to the top of the tire with the vehicle's weight on it for most accurate results.

Q3: Does this account for gear ratios?
A: No, this assumes a 1:1 gear ratio. For different ratios, multiply the result by your gear ratio.

Q4: Why use 4250 RPM specifically?
A: This is a common engine speed for performance testing, but you can adapt the formula for other RPM values.

Q5: How does tire wear affect the calculation?
A: Worn tires have smaller diameters, which would result in lower speed at the same RPM.