1. What is a Speed By Gear 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 in different gears.

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)
• 1056 — Conversion factor (combines inches to miles and minutes to hours)

Explanation: The formula calculates how far the vehicle travels per minute based on tire circumference and gear ratios, then converts to miles per hour.

3. Importance of Speed Calculation

Details: Accurate speed calculations help with gear selection, performance tuning, fuel efficiency optimization, and transmission design.

4. Using the Calculator

Tips: Enter engine RPM, tire diameter (measured from ground to top of tire × 2), current gear ratio, and axle 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 center of the wheel hub and multiply by 2, or check manufacturer specifications.

Q2: Where can I find my gear and axle ratios?
A: Check your vehicle's manual, manufacturer specifications, or look for identification tags on the transmission/differential.

Q3: Why is the conversion factor 1056?
A: It combines 63360 (inches per mile) divided by 60 (minutes per hour) = 1056.

Q4: Does this account for tire slippage or deformation?
A: No, this calculates theoretical speed. Actual speed may vary due to tire flex, slippage, or load.

Q5: Can I use this for different gear positions?
A: Yes, just input the appropriate gear ratio for each gear position (1st, 2nd, etc.).