1. What is a Gear And Tire Calculator?

Definition: This calculator estimates vehicle speed based on engine RPM, tire diameter, and gear 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 (miles per hour)
• \( RPM \) — Engine revolutions per minute
• \( TD \) — Tire diameter (inches)
• \( GR \) — Gear ratio (unitless)

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

3. Importance of Gear and Tire Calculations

Details: Proper gear and tire matching ensures optimal vehicle performance, fuel efficiency, and prevents engine strain.

4. Using the Calculator

Tips: Enter engine RPM, tire diameter in inches, and gear ratio (e.g., 3.73 for common rear-end ratios). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is the constant 1056 in the formula?
A: It combines unit conversions (inches to miles, minutes to hours) and π (pi) to simplify the calculation.

Q2: How do I measure tire diameter?
A: Measure from ground to top of tire when properly inflated, or use manufacturer specifications.

Q3: What affects gear ratio selection?
A: Vehicle weight, intended use (racing vs. towing), engine power band, and desired fuel economy.

Q4: Does this account for tire slippage?
A: No, this calculates theoretical speed. Actual speed may vary due to traction conditions.

Q5: Can I use this for transmission gear ratios?
A: Yes, multiply transmission gear ratio by final drive ratio for total GR.