1. What is the Quarter Mile Gear Ratio?

The Quarter Mile Gear Ratio helps determine the optimal gear ratio for a car's performance in quarter-mile drag racing. It considers engine RPM, tire diameter, and target speed to find the ideal gear ratio for maximum acceleration.

2. How Does the Calculator Work?

The calculator uses the gear ratio equation:

Where:

• \( RPM \) — Engine revolutions per minute at finish line
• \( \text{Tire Diameter} \) — Diameter of rear tires in inches
• \( MPH \) — Target quarter-mile speed in miles per hour
• 336 — Constant to convert units

Explanation: The equation calculates the gear ratio needed to achieve a specific MPH at the finish line while maintaining optimal RPM.

3. Importance of Gear Ratio Calculation

Details: Proper gear ratio is crucial for drag racing performance. It ensures the engine operates in its power band throughout the quarter-mile run, maximizing acceleration.

4. Using the Calculator

Tips: Enter engine RPM at finish line, tire diameter in inches, and target quarter-mile speed in MPH. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical gear ratio for quarter-mile racing?
A: Most drag cars use ratios between 3.50:1 and 4.10:1, but optimal ratio depends on many factors including engine power and weight.

Q2: How does tire diameter affect gear ratio?
A: Larger tires effectively create a higher gear ratio, while smaller tires create a lower ratio. This affects acceleration and top speed.

Q3: What's the significance of the 336 constant?
A: This number comes from unit conversion (5280 feet/mile ÷ (π × 60 min/hour × 12 in/ft)) to make the equation work with the given units.

Q4: Should I use trap RPM or shift point RPM?
A: Use your engine's RPM as you cross the finish line (trap RPM) for most accurate results.

Q5: How precise should my tire diameter measurement be?
A: Measure carefully - even 0.5 inch difference can significantly affect the calculation. Measure with the weight of the car on the tires if possible.