1. What is the Mark Williams Gear Ratio?

The Mark Williams gear ratio formula calculates the relationship between engine RPM, tire circumference, and vehicle speed. It's essential for performance tuning and transmission setup in racing applications.

2. How Does the Calculator Work?

The calculator uses the Mark Williams gear ratio equation:

Where:

• \( GR \) — Gear ratio (dimensionless)
• \( RPM \) — Engine revolutions per minute
• \( C \) — Tire circumference in inches
• \( MPH \) — Vehicle speed in miles per hour
• 336 — Constant for unit conversion

Explanation: The equation shows how many times the engine turns for each revolution of the wheels at a given speed.

3. Importance of Gear Ratio Calculation

Details: Proper gear ratio selection is crucial for optimizing acceleration, top speed, and engine performance in the desired RPM range.

4. Using the Calculator

Tips: Enter engine RPM, accurate tire circumference (measure rolling circumference for best results), and desired MPH. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is tire circumference important?
A: Tire size directly affects final drive ratio. Larger tires effectively create a taller gear ratio, while smaller tires create a shorter ratio.

Q2: What's a typical gear ratio range?
A: Street cars typically range from 2.5:1 to 4.5:1, while race cars may use ratios from 3.5:1 to 6.0:1 depending on application.

Q3: How do I measure tire circumference?
A: The most accurate method is to mark the tire and ground, roll the vehicle one complete revolution, and measure the distance traveled.

Q4: What's the 336 constant in the formula?
A: This converts units from inches and minutes to miles and hours (5280 ft/mile × 12 in/ft ÷ 60 min/hour = 1056, then 1056 ÷ π ≈ 336).

Q5: Can I use this for transmission gear selection?
A: Yes, this helps determine optimal transmission and final drive ratios for your performance goals.