How to Create a Bicycle Gearing Chart

Bicycle gear ratios determine how many inches your bike moves per pedal stroke. The gear ratios are calculated in with tire size, crank length, chain ring teeth and rear cog teeth to give a listing of gear inches, or distance traveled. Charting these measurements on a gearing chart and understanding where your bike overlaps in gears can give you a significant advantage on the road.

Things You'll Need

• Pencil
• Paper
• Calculator

Instructions

1. Take a look at your bike, and measure your crank arm's length. Oftentimes, this is on the side, but you may need to measure. It is in millimeters and typically ranges from 160 to 175. Write this down.

2. Find out your wheel size. This is typically listed on your tire. You need to know the width of your tire, as well, so make sure you write down both of those numbers (e.g.,700 x 23C).

3. Examine your front chain rings, and count the number of teeth on each. Sometimes, the rings have the number of teeth stamped into them. Write down the numbers for all three chain rings, if you have a triple set, and for both chain rings, if you have a double set.

4. Count the number of cogs on the rear cassette and the number of teeth on each cog. Write down each cog's corresponding number.

5. Use a calculator (if you need to) or visit Sheldon Brown's Gear Calculator using the link in the Resource section below. If you want to do the math, continue reading. Make a graph that has the chain ring teeth on the x-axis and the cog teeth on the y-axis.

6. Divide the radius of the wheel (e.g., a 680 mm wheel has a radius of 340 mm) by the crank arm length (e.g., 340 / 170 = 2.0).

7. Divide the front chain ring's number of teeth by the rear cog's number of teeth for the gear you want to calculate.

8. Multiply the numbers from Steps 6 and 7 to get the number of gear inches or inches the bike will travel for each rotation of the pedal around the bottom bracket.

9. Fill this number in at its corresponding part on the graph, and repeat Steps 6 through 8, until the chart is full.

References

• Sheldon Brown: Gain Ratios - A New Way to Designate Bicycle Gears

Resources

• Sheldon Brown's Gear Calculator