1. What is the Transmission Gear Ratio RPM Equation?

The Transmission Gear Ratio RPM equation calculates engine revolutions per minute (RPM) based on vehicle speed, transmission gear ratio, final drive ratio, and tire circumference. It's essential for understanding vehicle performance and gear selection.

2. How Does the Calculator Work?

The calculator uses the equation:

Where:

• \( RPM \) — Engine revolutions per minute
• \( MPH \) — Vehicle speed in miles per hour
• \( TGR \) — Transmission gear ratio (dimensionless)
• \( FGR \) — Final gear ratio (dimensionless)
• \( C \) — Tire circumference in inches
• 336 — Conversion factor combining various unit conversions

Explanation: The equation accounts for how vehicle speed translates to engine speed through the gear ratios and tire size.

3. Importance of RPM Calculation

Details: Knowing the RPM at different speeds helps with gear selection, fuel efficiency optimization, and preventing engine over-revving. It's crucial for performance tuning and transmission design.

4. Using the Calculator

Tips: Enter speed in MPH, both gear ratios as dimensionless numbers (e.g., 3.73), and accurate tire circumference in inches. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: How do I measure tire circumference?
A: Measure from ground to axle center (radius), multiply by 2π, or roll the tire one revolution and measure distance traveled.

Q2: Why is 336 used in the formula?
A: It combines unit conversions: 5280 feet/mile × 12 inches/foot ÷ 60 minutes/hour ≈ 336.

Q3: What's a typical RPM range for highway driving?
A: Most vehicles cruise at 1500-3000 RPM in top gear, but this varies by engine design and vehicle type.

Q4: How does changing tire size affect RPM?
A: Larger tires decrease RPM at given speed, while smaller tires increase RPM (with all else equal).

Q5: Can I use this for metric units?
A: You would need to adjust the formula for km/h and mm circumference, using a different conversion factor.