1. What is a Drag Racing Gear Calculator?

Definition: This calculator determines the optimal gear ratio for drag racing based on engine RPM, tire diameter, vehicle speed, and final drive ratio.

Purpose: It helps racers and mechanics optimize gear ratios for maximum acceleration and performance in drag racing applications.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( GR \) — Gear ratio (dimensionless factor)
• \( RPM \) — Engine revolutions per minute
• \( TD \) — Tire diameter (inches)
• \( MPH \) — Vehicle speed (miles per hour)
• \( FD \) — Final drive ratio (dimensionless factor)
• 336 — Constant to convert units

Explanation: The formula calculates the gear ratio needed to achieve a specific speed at a given RPM, accounting for tire size and final drive ratio.

3. Importance of Gear Ratio Calculation

Details: Proper gear ratio selection ensures the engine operates in its optimal power band throughout the race, maximizing acceleration and performance.

4. Using the Calculator

Tips: Enter the engine RPM at the finish line, tire diameter in inches, target speed in MPH, and final drive ratio (default 1.0). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the significance of the 336 constant?
A: This constant combines unit conversions (inches to miles, minutes to hours) and π (pi) to simplify the formula.

Q2: How do I measure tire diameter accurately?
A: Measure from the ground to the top of the tire and multiply by 2, or use manufacturer specifications for unloaded diameter.

Q3: What's a typical final drive ratio?
A: Most rear-end gear ratios range from 3.08 to 4.56 for street/strip cars, with higher numbers for drag racing.

Q4: Should I use trap speed or target speed?
A: Use your expected trap speed (finish line speed) for quarter-mile calculations.

Q5: How does this relate to transmission gear ratios?
A: This calculates the overall gear ratio. You'll need to consider transmission gear ratios separately when selecting gears.