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Bike Science: Machismo and your ‘gain ratio’

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(Photo © J. Maus)

[This is our latest Bike Science column by Shawn Small. Read previous entries here.]

In the world of singlespeeds and fixed gears you often hear people talking about each other’s “gear-inches”. This is an easy way to prove your machismo and is also a way to get useful data about your riding style. Today on Bike Science, I’ll take a closer look at gear-inches and explain why I prefer to use the concept of “gain ratio” to out-macho my friends.

The gear-inch is calculated simply by knowing the following information:

On my fixed-gear bike I run a 39 tooth chainring and 16 tooth cog on a 700×23 tire.

The gear-inch is useful to roughly know how hard or easy it is to pedal for trash talk. But it doesn’t take your crank arm length into account, which is a significant factor in determining the mechanical advantage of your drivetrain. That’s why I prefer to use the “gain ratio” developed by Sheldon Brown as a means to compare my machismo to others. (Note that it’s usually received by others with confusing looks.)

The Gain-Ratio is calculated by knowing the following information:

This ratio can be used as (1 : 4.69); meaning for every inch or mm my feet pedal, the bicycle goes 4.69 inch or mm forward. (Note: Remember to avert unit disaster by using either inches or millimeters.)

With the holiday weekend upon us, perhaps you’ll have time to play with these measurements. Whether you use them to trash talk with friends or just to satisfy your inner bike scientist is up to you.

Further reading:
Gain Ratios: A New Way to Designate Bicycle Gears, by Sheldon Brown
— Sheldon Brown’s handy Gear Calculator

— Bike Science is written by Shawn Small and is sponsored by: – GPS cycling, virtual competitions and detailed ride analysis.