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The Race Car Gear Ratio Calculator estimates vehicle speed (MPH) based on engine RPM, tire diameter, and gear ratio. It's essential for racers to optimize performance by selecting the right gear ratios for their track conditions.
The calculator uses the following equation:
Where:
Explanation: The equation calculates how fast the vehicle is moving based on how fast the engine is turning (RPM), the size of the tires, and the gear reduction between the engine and wheels.
Details: Proper gear ratio selection is crucial for optimizing acceleration, top speed, and engine performance within the power band. Racers use this calculation to select final drive ratios and transmission gearing.
Tips: Enter RPM (engine speed), tire diameter in inches, and gear ratio. All values must be positive numbers. Measure tire diameter accurately for best results.
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 divided by 2π.
Q2: What is a typical gear ratio for race cars?
A: This varies widely by application. Drag cars might use 4.10:1 or higher, while road course cars often use 3.23:1 to 3.73:1 ratios depending on track configuration.
Q3: Why is 336 the conversion factor?
A: The factor combines conversions for inches to miles (63360), minutes to hours (60), and accounts for π (3.1416) in the circumference calculation (63360/(60*π) ≈ 336).
Q4: How does tire growth at speed affect calculations?
A: At very high speeds, tires can grow significantly (especially drag radials), which will make actual speed slightly higher than calculated. This effect is typically 1-3%.
Q5: Can I use this for transmission gear selection?
A: Yes, you can calculate speed in each gear by using the product of the transmission gear ratio and final drive ratio as your GR value.