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Vehicle Speed Equation:
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The vehicle speed equation calculates the speed of a vehicle based on engine RPM, tire diameter, and gear ratio. It's essential for automotive enthusiasts, mechanics, and engineers to understand vehicle performance characteristics.
The calculator uses the following equation:
Where:
Explanation: The equation accounts for the relationship between engine speed, tire size, and gear reduction to determine vehicle speed.
Details: Understanding this relationship helps in selecting proper gear ratios for performance or fuel economy, diagnosing drivetrain issues, and planning vehicle modifications.
Tips: Enter engine RPM, tire diameter in inches, and gear ratio. All values must be positive numbers. For accurate results, measure tire diameter precisely.
Q1: How do I measure tire diameter accurately?
A: The most accurate method is to measure the rolling radius by marking the tire and ground, rolling the vehicle one revolution, and measuring the distance traveled.
Q2: What is a typical gear ratio?
A: Final drive ratios typically range from 2.73 to 4.10 for passenger vehicles, with higher numbers providing more acceleration but lower top speed.
Q3: Does this account for transmission gear ratios?
A: This calculates speed for a given gear. You'll need to multiply transmission gear ratio by final drive ratio for the total GR in a specific gear.
Q4: Why is the conversion factor 336?
A: It combines conversions for inches to miles (63360), minutes to hours (60), and accounts for π (3.1416) in circumference calculations.
Q5: How does tire wear affect calculations?
A: As tires wear, diameter decreases, which will slightly increase speed at the same RPM (about 1-2% over tire life).