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3.3.3.3 Rear shock
A rear shock is primarily fitted to mountain bikes
and helps to protect the ebike and rider against
impacts and vibrations caused by uneven
ground. A rear shock travels when a coil
spring, air suspension, or both suspension
types act on it.
Sag
The sag is the percentage of total spring
deflection that is compressed by the rider's
body weight, including equipment (such as a
backpack), their seating position and frame
geometry. Sag is not caused by riding.
Figure 15: Optimum rear shock ride performance
When optimally adjusted, the rear shock
counteracts deflection, stays higher in its
Figure 16: Optimum rear shock ride performance on hilly terrain
The rear shock rebounds at a controlled speed if
it is optimally adjusted. The rear wheel does not
bounce off rough surfaces or the ground; it stays
in contact with the ground instead
(blue line).
The saddle is raised slightly if the bump is
compensated and gently sinks downwards when
the suspension travels as soon as the wheel
touches the ground after the bump. The rear
shock rebounds in a controlled way, so that the
rider remains sitting in a horizontal position
when the next bump is absorbed. The
suspension motion is predictable and controlled.
The rider is not thrown upwards or forwards
(green line).
deflection range and helps to maintain speed
when riding on hilly parts of terrain.
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