Understand the development ratios in BMX Race

In BMX Race, the choice of good development is essential to optimize its starts, reminders and technical passages. At pride racing , we help you see more clearly, especially on an often overlooked point: the impact of the tire size on the development .

• What is BMX development?

Development (also called Gear Ratio ) corresponds to the distance traveled at each complete pedal turn. It is influenced by three main elements:

• the tray (number of teeth),

• Pignon (number of teeth),

• The real wheel diameter , which depends strongly on tire size Used.

but to go further, you have to distinguish two main ways of measuring this development:

Ratio, gear inches and roll out: what difference?

1. Gear ratio (raw transmission ratio)

This is simply the relationship between the number of teeth on the tray and gable.

• Example: 44 teeth/16 teeth = 2.75
< means that for 1 pedal lap, the rear wheel runs 2.75 times.

2. Gear inches

This is the transmission ratio multiplied by the real diameter of the wheel in inches .

• This gives a abstract value but useful to compare setups. Example: with a 20 "workforce tire and a 2.75 ratio → gear inches = 55"

The higher this figure, the more the bracquet is "long".

3. Roll out (development in meters or thumbs)

it's distance really traveled on the ground in a pedal turn , taking into account the tire circumference. meters or in inches traveled.

• Example: roll out = ~ 5.58 m with a 44x16 setup + tioga powerblock tire.

In summary:

• gear ratio = ratio brut

• gear Imps = Comparison between setups

• roll out = real distance traveled on the ground

• ‍♂️ why is the size of the tire crucial?

two tires displaying the same nominal size (for example 20x1.75) can have different active diameters depending on the different mark, pressure or type of carcass. And this diameter directly influences the distance traveled by pedal turn.

• a larger tire = longer development
• A smaller tire = shorter development