1. What is a Speed Calculator RPM?

Definition: This calculator estimates vehicle speed based on engine RPM, tire diameter, gear ratio, and axle ratio.

Purpose: It helps automotive professionals and enthusiasts determine vehicle speed at specific RPMs for gear selection and performance tuning.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (miles per hour)
• \( RPM \) — Engine revolutions per minute
• \( TD \) — Tire diameter (inches)
• \( GR \) — Gear ratio (unitless)
• \( AR \) — Axle ratio (unitless)

Explanation: The formula converts rotational motion to linear speed, accounting for all drivetrain reduction ratios and tire circumference.

3. Importance of Speed Calculation

Details: Accurate speed calculation helps in gear selection, fuel efficiency optimization, and performance tuning.

4. Using the Calculator

Tips: Enter the engine RPM, tire diameter in inches, gear ratio (default 1), and axle ratio (default 1). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the 1056 constant in the formula?
A: It converts inches per minute to miles per hour (12 inches/foot × 5280 feet/mile ÷ 60 minutes/hour).

Q2: How do I measure tire diameter accurately?
A: Measure from ground to top of tire with vehicle weight on it, or use manufacturer specs.

Q3: What if I don't know my gear ratio?
A: Use 1 for direct drive (no reduction), or consult your vehicle's specifications.

Q4: Why does speed vary with tire size?
A: Larger tires cover more distance per revolution, effectively changing the final drive ratio.

Q5: Can I use this for different units?
A: This calculator uses inches and mph. For metric, convert values or use a different constant.