What is the purpose of shifting?
If you want to go faster, you have to turn the pedals faster. Quickly, the speed of rotation of the pedals is too important, you run out of steam without taking a lot of speed.
Shifting allows the bike to go at very different speeds while the rider turns the pedals at a constant speed.
It is for an absolutely identical reason that there is a gearshift on a car: its engine, like the cyclist, has a rotation speed which makes the maximum efficiency. For the geeky cyclist, it is, roughly speaking, one pedal turn per second.
There are two types of gear changes:
1) The derailleur:
It allows the chain to pass from one gear to another. There is a “rear” derailleur to change sprocket (name of the sprockets of the rear wheel axle). There is a “front” derailleur to change the plate (name of the cycling gears of the axis driven by the pedals)
2) The gearbox:
It’s a box that is in the axis of the rear wheel.
These two systems produce the same effect.
Discovery of the gear change:
The discovery is done on a vast flat ground without obstacle. You never look at the wrists / joysticks that you will operate to change gears. With the derailleur system, at a standstill by lifting the rear wheel and turning the pedals by hand (do this manipulation with two), you put the chain on the smallest development (small plate and large pinion).
Then you put on the biggest development (large plateau and small gable). With a gearbox bike, before you start you put the controller on the lowest number, you test. Then you put it on the biggest number then you test.
Handling the gearshift:
With a derailleur bike, you put the chain on the middle chain if the bike has a “front” derailleur. To change gears, it is always necessary to pedal (so that the chain passes from one cogwheel to another) but at the moment of the change, you press very weakly on the pedals.
With a bike with a gearbox, you do not have to pedal but if you pedal at the time of the change, as with the other system, you have to release the pressure on the pedals. The bike has little inertia, your speed often varies. So you must change gears very often, as soon as you pedal a little too fast or a little too slowly.