Development Meters: Understanding Bicycle Gearing Through Distance

Development Meters: Understanding Bicycle Gearing Through Distance
Photo by Ben Guernsey / Unsplash

Development meters, or meters of development, is a measurement that specifies how many meters a bicycle will travel with a single revolution of the crank. It's commonly used to assess bicycle gearing, especially in countries that use the metric system.

Development meters illustrate how specific gear ratios translate to real-world performance by expressing bicycle gearing as a distance traveled.

This article will explain how to calculate meters of development and its practical use.

Calculating wheel circumference

The first step to understanding meters of development is knowing how to calculate the drive wheel's circumference. Thisis the distance the wheel rolls with one full rotation.

To calculate a wheel's circumference, multiply the wheel's diameter in meters by π (approximately 3.14).

wheel circumference = π * wheel diameter

For example, a 700c wheel with a gravel tire will commonly have a diameter of around 0.7 meters. Multiplying this by π tells us the wheel will travel about 2.2 meters per rotation.

Understanding gear ratios

The second component of understanding meters of development is gear ratios. They show how many times the rear wheel rotates with each pedal rotation. Different gear size combos rotate the rear wheel by different amounts with each pedal rotation.

Gear ratios are calculated by dividing the number of teeth on the front chainring by the number of teeth on the rear sprocket.

gear ratio = front teeth / rear teeth

This gives you a ratio that relates pedal revolutions to drive wheel revolutions. For example, with a 42-tooth front chain ring and a 15-tooth sprocket, your gear ratio would be 42 divided by 15, or 2.8. This means the rear wheel rotates 2.8 times for every rotation of the pedals.

Calculating meters of development

We can calculate meters of development by combining what we know about wheel circumference and gear ratios.

The gear ratio is the number of times the rear wheel rotates for each full rotation of the pedals. The wheel circumference is the distance the wheel will roll each time it rotates. Therefore, multiplying the circumference by the gear ratio tells us how far the bike will travel with each rotation of the pedals, or meters of development.

meters of development = gear ratio * wheel circumference

We get the full calculation by breaking it down further with our previous formulas for gear ratio and wheel circumference.

meters of development = front teeth / rear teeth * π * wheel diameter

Now we can calculate the distance any bike will travel using any combination of gears.

Meters of development vs gear inches

You may have heard of a similar measurement, gear inches. It's a simpler calculation that provides an easy way to compare gears. The formula for gear inches is the front teeth divided by the rear teeth, multiplied by the wheel's diameter.

gear inches = front teeth / rear teeth * wheel diameter

Meters of development is more cumbersome to use than gear inches because it requires calculating with the irrational constant, π, which gear inches doesn't need.

You can see how the two formulas differ when you compare them. The inclusion of π in the meters of development formula is where the distance traveled comes into play.

Calculating gear inches is easier, but relating it to real-world use is harder. Meters of development rationalizes bicycle gearing by relating it to actual distances.

Comparing gears

You can calculate development meters for different gear combinations and then compare them. This will give you an idea of how the bike will perform in one versus the other.

For example, if you had a 1x gravel bike with a 40T chainring, 10-44T rear cassette, and 700c wheels (~0.7 meter tire diameter), you can compare the two highest gears. You can compare 40:10 and 40:11, which result in 8.79 development meters and 7.99 development meters respectively.

With each pedal rotation in the highest gear, you'll go 0.8 meters further vs the next one lower. Of course, you will have to pedal harder with each pedal stroke for that increased movement, but you can start to see how the two relate to each other.

It's useful to compare sequential gears to understand the relative steps between them. As sprockets get larger, bigger jumps in their number of teeth are needed to make the effort between each feel consistent.

Meters of development is more common in countries that use the metric system, and it is foundational for understandingbicycle gearing. It rationalizes different gear combinations in terms of distance traveled, which is the entire point of these machines, isn't it?