1. What is a Gear Ratio and Speed Calculator?

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

Purpose: It helps automotive enthusiasts, mechanics, and engineers determine vehicle speed at specific RPMs with given gear ratios.

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)
• \( GR \) — Transmission gear ratio (unitless)
• \( AR \) — Axle ratio (unitless)

Explanation: The formula converts rotational speed to linear speed while accounting for gear reduction and tire circumference.

3. Importance of Gear Ratio Calculations

Details: Proper gear ratio calculations help optimize vehicle performance, fuel efficiency, and towing capacity.

4. Using the Calculator

Tips: Enter RPM, tire diameter in inches, gear ratio (e.g., 1.0 for direct drive), and axle ratio (e.g., 3.73). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the 1056 constant in the formula?
A: It combines unit conversions (inches to miles, minutes to hours) and π/12 for tire circumference.

Q2: How do I measure tire diameter?
A: Measure from ground to top of tire (loaded) or calculate from tire size markings (e.g., 275/60R15).

Q3: What's a typical gear ratio?
A: Varies by vehicle: 1st gear might be 3.5:1, overdrive could be 0.7:1. Final drive ratio combines transmission and axle ratios.

Q4: Does this account for torque converter slip?
A: No, for automatic transmissions, actual speed may be slightly lower due to converter slip.

Q5: How accurate is this calculation?
A: Very accurate for manual transmissions in gear. For automatics, expect ±3% variance due to slip.