1. What is the Final Drive Ratio Calculator?

The Final Drive Ratio Calculator helps determine the effective gear ratio when changing tire sizes. It accounts for how different tire diameters affect your vehicle's final drive ratio, which impacts acceleration, fuel economy, and speedometer accuracy.

2. How Does the Calculator Work?

The calculator uses the effective ratio formula:

Where:

• \( Ratio \) — Original gear ratio (dimensionless)
• \( New\ Diam \) — New tire diameter (inches)
• \( Old\ Diam \) — Original tire diameter (inches)

Explanation: The formula shows how changing tire size affects your effective gear ratio. Larger tires effectively decrease your ratio while smaller tires increase it.

3. Importance of Effective Ratio Calculation

Details: Calculating the effective ratio is crucial when modifying vehicles to understand how tire size changes will affect performance characteristics like acceleration, top speed, and odometer readings.

4. Using the Calculator

Tips: Enter your original gear ratio, old tire diameter, and new tire diameter (all in inches). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: How do I measure tire diameter?
A: You can calculate tire diameter using the formula: (Width * Aspect Ratio / 100 * 2 / 25.4) + Wheel Diameter.

Q2: What's a typical gear ratio range?
A: Passenger cars typically range from 2.5:1 to 4.5:1, while trucks may have ratios up to 6:1.

Q3: How does ratio affect performance?
A: Higher ratios improve acceleration but reduce top speed and fuel economy. Lower ratios do the opposite.

Q4: Should I consider tire width too?
A: While width affects contact patch and grip, it doesn't directly affect the ratio calculation unless it changes the overall diameter.

Q5: How much ratio change is significant?
A: A 10% change in effective ratio is generally noticeable in driving characteristics.