A number of factors are decisive for this: chainring size at the front, rear sprocket set, wheel size and cadence. In addition, the required power is also important.
To better illustrate this with an example, we make the following assumptions for this purpose:
- chainring front: 40 teeth
- rear sprocket: 10 teeth
- wheel size: 29 inch, wheel circumference 2.31 m
- cadence: 60 rpm
Transmission:
The gear ratio is the ratio of the number of teeth between the chainring (front) and the sprocket (rear). In our example we have a gear ratio of 4 (40/10 = 4.). This means that the sprocket rotates 4x, while in this time the chainring rotates only 1x. Front chainring with 40 teeth and the rear sprocket with 10 teeth -> 40/10 = 4.
Deployment:
One rotation of the chainring corresponds to one crank rotation - the distance covered is referred as deployment (m). So how many meters are covered in one crank rotation.
One rotation of the rear sprocket corresponds to one rotation of the tire. In our example, the sprocket (and thus the tire) is rotated 4x in one crank rotation, thus resulting in: 4 x 2.31 m = 9.24 m. The deployment is with our gear ratio and with our 29 inch rear wheel thus 9.24 m.
Cadence:
The pedaling frequency (also called cadence) provides information about the rotation of the cranks. This is usually given in rounds per minute (rpm). A comfortable cadence is around 60 rpm - this corresponds to one complete pedal rotation per second. This is considered comfortable by most cyclists. According to various studies, the optimal cadence is around 100 rpm. Ideally, the bicycle gear should always be selected in such a way that the cadence remains constantly in the desired range (pleasant or optimal) - regardless of whether riding uphill or on a flat track.
Speed calculation:
These values can be used to calculate the possible speed. In our example, we now know how many meters we cover per crank rotation (= deployment) - 9.24 meters. At a comfortable cadence of 60 rotations per minute, this results in: 9.24 x 60 = 554.4 meters. 554.4 m/min x 0.06 = 33.26 km/h. So at this cadence we manage a speed of about 33 km/h, at an optimal cadence of 100 it would be 55.4 km/h.
However, this figure is only theoretically available as long as the power required for it cannot be provided. In practice, the parameter "power" is added. Rough guide value: hobby riders usually manage approx. 2.5 - 3.5 watts/kg (professional athletes are at approx. 6-7 watts/kg), with which the power is approx. 200-300 watts (again depending on duration etc.). However, the total power can be significantly increased by electrical support ...
You can find some useful calculators online, for example:
With multiple shifting, the different sprockets can be used to obtain different gear ratios and thus different unfoldings (deployment) so that pedal cadence and / or effort remain as consistent as possible regardless of the terrain.
We hope that we could give you a little more clarity on this topic and wish you a lot of fun with the development of your power.
