1. What is the Car Speed Equation?

The car speed equation calculates vehicle speed based on engine RPM, gear ratio, and tire circumference. It's essential for performance tuning, gear selection, and understanding vehicle dynamics.

2. How Does the Calculator Work?

The calculator uses the speed equation:

Where:

• \( RPM \) — Engine revolutions per minute
• \( Gear\ Ratio \) — Transmission gear ratio (including final drive)
• \( Tire\ Circumference \) — Distance traveled per tire revolution in inches
• 336 — Conversion factor combining unit conversions (miles, hours, inches)

Explanation: The equation converts rotational motion into linear speed, accounting for gear reduction and tire size.

3. Importance of Speed Calculation

Details: Accurate speed calculation helps in gear selection, performance optimization, fuel efficiency analysis, and verifying speedometer accuracy.

4. Using the Calculator

Tips: Enter RPM (typically 1500-7000 for most cars), gear ratio (e.g., 3.55 for common final drive), and measured tire circumference. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: How do I measure tire circumference?
A: Measure from ground to axle center (radius), multiply by 2π, or roll the tire one revolution and measure distance traveled.

Q2: Why 336 in the formula?
A: It combines conversions: 5280 ft/mile × 12 in/ft ÷ 60 min/hour = 1056, then 1056 ÷ π ≈ 336 for practical use.

Q3: Does this work for any gear?
A: Yes, but you must use the total gear ratio (transmission gear × final drive ratio).

Q4: How accurate is this calculation?
A: Very accurate if inputs are precise, but doesn't account for tire slip, deformation, or drivetrain losses.

Q5: Can I use metric units?
A: The formula requires inches for circumference and outputs mph. For km/h, use (RPM × Gear Ratio × Tire Circumference in cm) / 530.