1. What is a Gear And RPM Calculator?

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

Purpose: It helps automotive enthusiasts and mechanics 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)
• \( 1056 \) — Conversion factor (combines inches to miles and hours to minutes)

Explanation: The formula calculates how far the vehicle travels per minute based on tire circumference and gear reduction, then converts to miles per hour.

3. Importance of Gear Ratio Calculations

Details: Proper gear ratio selection affects acceleration, top speed, fuel efficiency, and engine longevity.

4. Using the Calculator

Tips: Enter engine RPM, measured tire diameter (from ground to top of tire × 2), and final drive gear ratio (including transmission gear if in a specific gear).

5. Frequently Asked Questions (FAQ)

Q1: How do I measure tire diameter accurately?
A: Measure from ground to top of tire (loaded) and multiply by 2, or use manufacturer specifications.

Q2: What's included in the gear ratio?
A: The product of transmission gear ratio and final drive (differential) ratio.

Q3: Why 1056 in the formula?
A: It combines conversion from inches to miles (63360) and minutes to hours (60): 63360/60 = 1056.

Q4: Does this account for tire slip or torque converter slip?
A: No, for automatic transmissions or performance applications, actual speed may be slightly lower.

Q5: Can I calculate RPM from speed?
A: Yes, rearrange the formula: \( RPM = \frac{S \times GR \times 1056}{\pi \times TD} \).