Gear Ratio Tire Size Speed Calculator

Speed Calculation Formula:

\[ Speed_{tire} = \frac{RPM}{GR} \times \frac{Tire_{Diam} \times \pi}{1056} \]

Speed (Speed_tire):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Gear Ratio Tire Size Speed Calculation?

The Gear Ratio Tire Size Speed Calculation determines vehicle speed based on engine RPM, gear ratio, and tire diameter. This formula is essential for automotive enthusiasts, mechanics, and engineers to understand vehicle performance characteristics.

2. How Does the Calculator Work?

The calculator uses the speed calculation formula:

\[ Speed_{tire} = \frac{RPM}{GR} \times \frac{Tire_{Diam} \times \pi}{1056} \]

Where:

\( RPM \) — Engine revolutions per minute
\( GR \) — Gear ratio (unitless)
\( Tire_{Diam} \) — Tire diameter in inches
\( \pi \) — Mathematical constant pi (approximately 3.14159)
1056 — Conversion factor to get MPH

Explanation: The formula calculates how engine RPM translates to wheel speed based on gear reduction and tire circumference, then converts to miles per hour.

3. Importance of Speed Calculation

Details: Accurate speed calculation is crucial for gear selection, performance tuning, fuel efficiency optimization, and understanding vehicle capabilities at different RPM ranges.

4. Using the Calculator

Tips: Enter RPM (typically 1000-7000 for most vehicles), gear ratio (common range 2.5-4.5 for final drive), and tire diameter (measured from ground to top of tire). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is the conversion factor 1056?
A: The factor 1056 converts inches per minute to miles per hour (63360 inches per mile ÷ 60 minutes per hour = 1056).

Q2: How do I measure tire diameter accurately?
A: Measure from ground to top of tire with proper inflation and vehicle weight, or use manufacturer specifications for unloaded diameter.

Q3: Does this account for tire slippage?
A: No, this calculates theoretical speed. Actual speed may vary due to tire slip, transmission efficiency, and other factors.

Q4: Can I use this for different transmission gears?
A: Yes, but you must use the overall gear ratio (transmission gear ratio × final drive ratio) for accurate results.

Q5: What if I have metric tire measurements?
A: Convert metric tire size to inches before using the calculator, or modify the formula to accept metric inputs.