1. What is the Speed from Gear Ratio and RPM Calculation?

This calculation determines vehicle speed based on engine RPM, tire circumference, and gear ratio. It's essential for automotive tuning, performance analysis, and gear selection.

2. How Does the Calculator Work?

The calculator uses the following equation:

Where:

• \( RPM \) — Engine revolutions per minute
• \( Tire\ Circumference \) — Distance traveled in one tire revolution (inches)
• \( Ratio \) — Overall gear ratio (transmission × final drive)
• 336 — Conversion factor for mph

Explanation: The formula converts engine RPM to wheel RPM using the gear ratio, then calculates distance traveled per hour based on tire circumference.

3. Importance of Speed Calculation

Details: Accurate speed calculation helps in gear selection for optimal performance, fuel efficiency, and ensuring speedometer accuracy.

4. Using the Calculator

Tips: Enter RPM (typically 1500-7000 for most vehicles), exact tire circumference (can be calculated from tire size), and total gear ratio. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: How do I find my tire circumference?
A: Measure the distance traveled in one tire revolution, or calculate from tire size: ((width × aspect ratio × 2) / 25.4) + wheel diameter × π.

Q2: What is a typical gear ratio?
A: Final drive ratios typically range from 2.5:1 to 4.5:1, multiplied by transmission gear ratio (often 0.5:1 to 4:1).

Q3: Why is 336 the conversion factor?
A: It combines unit conversions: (inches to miles) × (minutes to hours) = (5280 × 12) / 60 = 1056, then adjusted for wheel revolutions.

Q4: Does this work for any vehicle?
A: Yes, as long as you have accurate inputs for RPM, tire size, and gear ratio. Works for cars, trucks, motorcycles, etc.

Q5: How accurate is this calculation?
A: Very accurate for theoretical speed, but actual speed may vary slightly due to tire slip, wear, and other factors.