1. What is a Speed Gear Ratio Calculator?

Definition: This calculator estimates vehicle speed based on engine RPM, gear ratio, and a constant that accounts for tire size and other factors.

Purpose: It helps automotive enthusiasts and mechanics determine vehicle speed at specific RPMs for different gear ratios.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (miles per hour)
• \( RPM \) — Engine revolutions per minute
• \( GR \) — Gear ratio (unitless)
• \( C \) — Constant (default 0.002975 for typical tire size)

Explanation: The RPM is divided by the gear ratio to get wheel speed, then multiplied by a constant to convert to miles per hour.

3. Importance of Speed Calculation

Details: Accurate speed calculations help with gear selection, performance tuning, and ensuring legal speed compliance.

4. Using the Calculator

Tips: Enter the engine RPM, gear ratio, and constant (default 0.002975). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What affects the constant value?
A: The constant is primarily affected by tire diameter - larger tires increase the constant value.

Q2: How do I find my gear ratio?
A: Gear ratios can be found in your vehicle's specifications or by dividing the number of teeth on the driven gear by the driving gear.

Q3: Why is my actual speed different from calculated?
A: Differences can occur due to tire wear, slippage, transmission efficiency, or incorrect constant value for your specific tire size.

Q4: Can I use this for any vehicle?
A: Yes, but you may need to adjust the constant value based on your specific tire size and drivetrain configuration.

Q5: How do I calculate the constant for my tires?
A: Measure your tire's revolutions per mile (usually found in tire specs) and use: (60 ÷ revolutions per mile) × final drive ratio.