1. What is the Speed From Gear Ratio Calculator?

This calculator determines vehicle speed based on engine RPM, gear ratio, and tire circumference. It's useful for automotive enthusiasts, mechanics, and engineers to understand vehicle performance characteristics.

2. How Does the Calculator Work?

The calculator uses the following equation:

Where:

• \( RPM \) — Engine revolutions per minute
• \( Ratio \) — Combined gear ratio (transmission × final drive)
• \( Tire\ Circumference \) — Tire circumference in inches

Explanation: The equation converts engine RPM to wheel RPM through the gear ratio, then calculates distance traveled per minute based on tire circumference, and finally converts to miles per hour.

3. Importance of Speed Calculation

Details: Understanding the relationship between RPM and speed helps in gear selection, fuel efficiency optimization, and performance tuning. It's also useful for diagnosing drivetrain issues.

4. Using the Calculator

Tips:

• Measure tire circumference accurately by rolling the tire one revolution and measuring the distance
• For combined gear ratio, multiply transmission gear ratio by final drive ratio
• Use actual RPM values from a tachometer for most accurate results

5. Frequently Asked Questions (FAQ)

Q1: How do I find my gear ratio?
A: Check your vehicle specifications or measure by counting driveshaft rotations versus wheel rotations (with one wheel off the ground).

Q2: Why is tire circumference important?
A: Larger tires cover more distance per revolution, effectively changing your final drive ratio and speed at any given RPM.

Q3: How accurate is this calculation?
A: It provides theoretical speed. Actual speed may vary due to tire slippage, load, and other factors.

Q4: Can I use this for different gear positions?
A: Yes, just input the appropriate gear ratio for each gear position.

Q5: What if my speedometer is off after changing tires?
A: This calculator can help you understand how much your speedometer might be off after changing tire size.