1. What is the Sheldon Brown Gear Calculator?

The Sheldon Brown Gear Calculator computes the gain ratio of a bicycle drivetrain, which provides a more accurate measure of mechanical advantage than traditional gear inches. It was developed by the renowned bicycle mechanic Sheldon Brown.

2. How Does the Calculator Work?

The calculator uses Sheldon Brown's gain ratio equation:

Where:

• \( \text{Wheel Circumference} \) — The distance the wheel travels in one revolution (mm)
• \( \text{Crank Length} \) — The length of the crank arm from center to pedal (mm)
• \( \text{Gear Ratio} \) — The ratio of chainring teeth to cog teeth (dimensionless)

Explanation: The gain ratio accounts for both the gear ratio and the mechanical advantage provided by the crank length, giving a more complete picture of pedaling efficiency.

3. Importance of Gain Ratio

Details: Gain ratio helps cyclists compare different gear setups more accurately than gear inches alone. It's particularly useful when comparing bikes with different crank lengths or wheel sizes.

4. Using the Calculator

Tips: Enter wheel circumference in millimeters, crank length in millimeters, and gear ratio (chainring teeth divided by cog teeth). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why use gain ratio instead of gear inches?
A: Gain ratio accounts for crank length, making it more accurate for comparing different bike setups.

Q2: What are typical gain ratio values?
A: Most bicycles have gain ratios between 3 and 8. Lower values are easier to pedal, higher values provide more speed.

Q3: How do I measure wheel circumference?
A: Measure the distance the wheel travels in one complete revolution, or calculate using π × diameter.

Q4: What's a good gain ratio for climbing hills?
A: Lower gain ratios (3-5) are better for climbing, while higher ratios (6-8) are better for flat terrain and descending.

Q5: Does gain ratio affect cadence?
A: Yes, higher gain ratios require higher pedal force or lower cadence for the same speed.