FINAL GEAR RATIO (ON WHEELS-EQUIPPED VEHICLE)

Calculating the Final Gear Ratio

dynamo-gear distance circumference compare to wheel-circle distance circumference in same single rotation

To calculate the final gear ratio (also known as the Final Drive Ratio), you need to divide the number of teeth on the ring gear by the number of teeth on the pinion gear. This determines how many times the driveshaft must rotate to turn the wheels exactly once.

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The Formula

Use the following formula for your calculations:

Final Drive Ratio = Ring Gear Teeth / Pinion Gear Teeth

Example Calculation

If a differential has a ring gear with 41 teeth and a pinion gear with 11 teeth:

• Calculation: 41 / 11
• Result: 3.73:1

This means the pinion gear must spin 3.73 times for every 1 revolution of the wheels.

Understanding the Impact

Ratio Type	Characteristics
Higher (e.g., 4.10:1)	"Short" gearing. Improves acceleration and torque multiplication but lowers top speed and increases engine RPM at cruising speeds.
Lower (e.g., 3.07:1)	"Tall" gearing. Improves fuel efficiency and lowers cruising RPM but results in slower acceleration.

Considerations for Performance Tuning

1. Tire Diameter: Larger tires effectively "lower" your gear ratio (making it taller), while smaller tires "raise" it (making it shorter).
2. Power Band: Match the final drive to the engine's peak torque RPM to keep the engine in its power band more effectively.
3. Transmission Ratios: Always multiply your transmission gear ratio by the final drive ratio to calculate your "Total Drive Ratio" for each specific gear.

Are you looking to calculate the total drive ratio for a specific vehicle setup you are currently working on?