Since external derailleur gear systems are located on the outside of
the bicycle and are not equipped with any protection, you should, if
possible, wear tightly fitting trousers or use a clip to secure trouser legs
so that they do not get pinched by the chain or cogs. This reduces the
risk of falls.
We can distinguish three types of shifters: grip shifts (Figure 20/1), shift
levers (Figure 20/2) and combined brake and shift levers (Figures 20/3
and 20/4).
Shift levers have two functions: you can switch to a bigger cog with your
thumb, or to a smaller one with your index finger. This means that by
applying pressure to the left-hand side shifter with your thumb the front
derailleur will move to a bigger chainring, resulting in a more demanding
transmission ratio. The same movement on the right-hand side shifter
produces an easier transmission. Grip shifts work on a similar principle.
In general, if you rotate the grip shift towards yourself, you switch to a
bigger cog, and in the opposite direction to a smaller one.
On combined brake- and shift levers the same lever functions as both
brake and shift lever. Pull the lever to brake, and rotate it to shift between
gears. Nowadays, use of this system has spread beyond racing bikes.
Derailleurs
The derailleur gears of the bicycle bring the rider's performance
and desired speed in line with terrain conditions. Derailleur gears
do not affect the amount of physical work to be performed, as
work= force x distance. Derailleur gears basically influence the
amount of force that needs to be exerted and the distance
travelled. In practice, this means that if you shift to a low gear
when riding uphill, you will need to exert only a small amount of
force, but due to the high number of pedal turns you will travel
more slowly.
If you shift to a high gear when cycling downhill, you will travel a
greater distance with a single turn of the pedal, and accordingly
will travel faster.
To be able to ride even longer distances without getting exhausted
and to utilise your optimum performance, cycle with a cadence of
70 - 100 (number of crank revolutions per minute).
External derailleur
gear systems
External derailleur gear
systems consist of the
following: front and rear
derailleurs and shifters.
The task of the front
derailleur (Figure 18) is to
move the chain between the
front chainrings (2 or 3
chainrings). With the rear
derailleur (Figure 19) the
correct transmission ratio
can be selected from usually
10 rear cogs. Derailleurs
can be operated with the
shifters mounted on the
handlebar. In most cases,
the left-hand side shifter
controls the front, and the
right-hand side the rear
derailleur.
Figure 20/1
Figure 20/2
Figure 20/3
Figure 20/4
Figure 19
Figure 18
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ENGLISH
