1. What is an RPM Tire Size Speed Calculator?

Definition: This calculator estimates vehicle speed based on engine RPM and tire diameter.

Purpose: It helps automotive enthusiasts, mechanics, and engineers determine vehicle speed at specific RPMs for gear ratio planning or performance tuning.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (miles per hour)
• \( RPM \) — Engine revolutions per minute
• \( \pi \) — Pi (approximately 3.1416)
• \( TD \) — Tire diameter (inches)
• 1056 — Conversion factor for units

Explanation: The formula calculates the distance traveled per minute (circumference × RPM) and converts it to miles per hour.

3. Importance of Speed Calculation

Details: Accurate speed estimation helps in gear ratio selection, fuel efficiency optimization, and performance tuning.

4. Using the Calculator

Tips: Enter the engine RPM and tire diameter in inches. For accurate results, measure the actual loaded tire diameter rather than using the nominal size.

5. Frequently Asked Questions (FAQ)

Q1: Why is the conversion factor 1056?
A: It converts inches per minute to miles per hour (12 inches/foot × 5280 feet/mile ÷ 60 minutes/hour).

Q2: Does this account for gear ratios?
A: No, this assumes direct drive (1:1 ratio). For other ratios, use the RPM at the wheels (engine RPM ÷ gear ratio).

Q3: How do I measure tire diameter?
A: Measure from ground to top of tire under normal load, or calculate: (wheel diameter) + 2×(sidewall height).

Q4: Why does my actual speed differ?
A: Factors like tire slippage, inflation, wear, and transmission efficiency can affect real-world speed.

Q5: Can I use this for metric units?
A: For km/h, use the formula: \( S = \frac{RPM \times \pi \times TD}{1056} \times 1.60934 \)