1. What is a Speed Calculator From Gear Ratio?

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 theoretical vehicle speed for given RPM and gear combinations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (mph)
• \( RPM \) — Engine revolutions per minute
• \( GR \) — Gear ratio (unitless)
• \( C \) — Constant (typically 0.00595 for mph with standard tire size)

Explanation: The RPM is divided by 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 estimation helps in gear selection, performance tuning, and ensuring the vehicle operates within optimal RPM ranges.

4. Using the Calculator

Tips: Enter the engine RPM, gear ratio (default 1), and constant (default 0.00595). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What affects the constant value?
A: The constant depends on tire diameter, final drive ratio, and unit conversion factors.

Q2: What's a typical gear ratio?
A: Gear ratios vary widely but common final drive ratios range from 3.23 to 4.10 for passenger vehicles.

Q3: When would I change the constant?
A: Adjust when changing tire size - larger tires increase the constant, smaller tires decrease it.

Q4: How accurate is this calculation?
A: It provides theoretical speed - actual speed may vary due to tire slip, load, and other factors.

Q5: Can I use this for different speed units?
A: Yes, but you'll need to adjust the constant accordingly (0.00956 for km/h).