1. What is RPM Calculation From Gear Ratio And Speed?

The RPM calculation from gear ratio and speed determines the rotational speed of an engine or motor based on vehicle speed, gear ratio, and tire diameter. This is essential for automotive engineering, performance tuning, and mechanical system design.

2. How Does the Calculator Work?

The calculator uses the RPM formula:

Where:

• \( Speed_{mph} \) — Vehicle speed in miles per hour
• \( GR \) — Gear ratio (unitless)
• \( Tire_{Diam} \) — Tire diameter in inches
• 336 — Constant conversion factor

Explanation: The formula converts linear vehicle speed to rotational engine speed using the gear ratio and tire circumference relationship.

3. Importance of RPM Calculation

Details: Accurate RPM calculation is crucial for proper gear selection, fuel efficiency optimization, engine performance analysis, and preventing engine damage from over-revving.

4. Using the Calculator

Tips: Enter speed in mph, gear ratio as a decimal value (e.g., 3.73), and tire diameter in inches. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is 336 used in the formula?
A: The constant 336 combines unit conversion factors (5280 feet/mile, 12 inches/foot, 60 minutes/hour) divided by π (approximately 3.1416).

Q2: Can I use this for metric units?
A: This formula is specifically for mph and inches. For km/h and mm, a different constant would be needed.

Q3: What is a typical gear ratio range?
A: Gear ratios typically range from 2.5 to 4.5 for most vehicles, with lower ratios for fuel economy and higher ratios for performance.

Q4: How do I measure tire diameter accurately?
A: Measure from the ground to the top of the tire and double it, or use manufacturer specifications for the exact tire size.

Q5: Does this account for tire slippage?
A: No, this formula assumes perfect traction with no slippage. Actual RPM may vary slightly due to tire slip under acceleration.