1. What is a Gear Ratio Speed Calculator?

Definition: This calculator estimates vehicle speed in miles per hour 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 different gear combinations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Vehicle speed (mph)
• \( RPM \) — Engine revolutions per minute
• \( TD \) — Tire diameter (inches)
• \( GR \) — Transmission gear ratio
• \( AR \) — Axle ratio
• \( 1056 \) — Conversion constant (combines unit conversions)

Explanation: The formula calculates how many miles the vehicle travels per hour based on wheel rotations derived from engine RPM and gear reductions.

3. Importance of Speed Calculation

Details: Accurate speed calculations help in gear selection, performance tuning, and ensuring proper engine operation within optimal RPM ranges.

4. Using the Calculator

Tips: Enter engine RPM, tire diameter in inches, transmission gear ratio, and axle ratio (default 3.73). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: How do I measure tire diameter?
A: Measure from ground to top of tire (loaded) or calculate using tire size markings (e.g., 275/60R15 ≈ 28" diameter).

Q2: What's a typical axle ratio?
A: Common ratios range from 3.08 to 4.10 for street vehicles, with 3.23-3.73 being popular performance choices.

Q3: Why 1056 in the formula?
A: This constant combines conversions for inches to miles (63360), minutes to hours (60), and accounts for π (3.1416).

Q4: Does this account for tire slip or converter slippage?
A: No, this calculates theoretical speed. Actual speed may be 2-5% lower due to these factors.

Q5: How accurate is this calculator?
A: Very accurate for theoretical calculations when precise measurements are input. Real-world results may vary slightly.