Speed Formula:
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Definition: This calculator estimates vehicle speed based on tire revolutions per minute (RPM) and tire diameter.
Purpose: It helps automotive professionals and enthusiasts determine vehicle speed when direct speed measurement isn't available.
The calculator uses the formula:
Where:
Explanation: The formula converts tire rotation to linear distance traveled per minute, then to miles per hour.
Details: Understanding the relationship between RPM and speed helps with gear ratio selection, fuel efficiency optimization, and performance tuning.
Tips: Enter the tire RPM and tire diameter in inches. Both values must be > 0. The result shows the calculated speed in miles per hour.
Q1: How do I measure tire diameter?
A: Measure from the ground to the top of the tire (loaded radius) and multiply by 2, or check the tire specifications.
Q2: Why is the conversion factor 1056?
A: It converts inches per minute to miles per hour (12 in/ft × 5280 ft/mi ÷ 60 min/hr = 1056).
Q3: Does this account for tire wear or pressure?
A: No, use the actual measured diameter for most accurate results as tires wear or pressure changes affect diameter.
Q4: Can I use this for different speed units?
A: This calculator provides mph. For km/h, multiply the result by 1.60934.
Q5: How accurate is this calculation?
A: It's theoretically accurate if inputs are precise, but real-world factors like tire slip may cause variations.