1. What is a Speed Calculator Based On Gear Ratio?

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

Purpose: It helps automotive enthusiasts and mechanics determine vehicle speed at specific RPMs with different gear combinations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (mph)
• \( RPM \) — Engine revolutions per minute
• \( TD \) — Tire diameter (inches)
• \( GR \) — Gear ratio (unitless)
• \( AR \) — Axle ratio (unitless)
• 1056 — Conversion factor (combines inches to miles and minutes to hours)

Explanation: The formula calculates how tire rotation translates to distance traveled, then converts this to miles per hour.

3. Importance of Speed Calculation

Details: Accurate speed calculations help with gear selection, performance tuning, and ensuring speedometer accuracy.

4. Using the Calculator

Tips: Enter engine RPM, tire diameter (measured from ground to top of tire), gear ratio (transmission ratio), and axle ratio (differential ratio). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: How do I measure tire diameter accurately?
A: Measure from the ground to the top of the tire with proper inflation and vehicle weight on it.

Q2: Where can I find my gear and axle ratios?
A: Check your vehicle's manual or manufacturer specifications. Axle ratio is often stamped on the differential.

Q3: Why is the conversion factor 1056?
A: It combines 5280 (feet per mile) ÷ 12 (inches per foot) ÷ 60 (minutes per hour) × π ≈ 1056.

Q4: Does this account for tire slippage or deformation?
A: No, this is a theoretical calculation. Actual speed may vary slightly due to these factors.

Q5: Can I use this for different transmission gears?
A: Yes, just input the specific gear ratio for the transmission gear you're calculating.