1. What is a Gear Ratio Tire Size RPM Speed Calculator?

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

Purpose: It helps automotive enthusiasts and mechanics determine vehicle speed at specific RPMs for gear selection and performance tuning.

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)

Explanation: The formula calculates how much distance the vehicle travels per engine revolution based on tire circumference and drivetrain ratios.

3. Importance of Speed Calculation

Details: Accurate speed calculations help in gear selection, performance tuning, fuel efficiency optimization, and verifying speedometer accuracy.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: How do I measure tire diameter?
A: Measure from the ground to the top of the tire or use manufacturer specifications. For accuracy, measure with vehicle weight on the tires.

Q2: What's the 1056 constant in the formula?
A: This converts inches per minute to miles per hour (12 inches/foot × 5280 feet/mile ÷ 60 minutes/hour).

Q3: How does gear ratio affect speed?
A: Higher gear ratios (numerically lower) result in higher speeds at the same RPM, while lower ratios (numerically higher) provide more torque but lower speed.

Q4: Should I use loaded or unloaded tire diameter?
A: For most accuracy, use loaded diameter (with vehicle weight on tires) as this affects actual rolling circumference.

Q5: Can I use this for different transmission types?
A: Yes, the calculator works for manual, automatic, and CVT transmissions as long as you know the current gear ratio.