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SUSPEnSIon FoRKS
Most trekking bikes
equipped with suspension forks. This feature gives you better control
of your WHEELER bicycle when riding cross-country or on rough road
surfaces and ensures more ground contact for the tyre. It noticeably
reduces the strain on you and your bicycle caused by the mechanical
shocks from the terrain.
a
Suspension forks
ing. The suspension is usually provided by coil springs, special types
of plastic (elastomers) or sealed air compartments, or combinations of
these options. The damping is usually done by oil or by the self-damp-
ing properties of the elastomers.
I
b
Adjusting the Spring Rate
To work perfectly, the fork has to be adjusted to the weight of the rider,
the sitting posture and the intended use. The suspension forks should
yield by about 10-25 % of their total travel under the rider's weight.
Be sure to have this adjustment carried out by your WHEELER bicycle
dealer at the time of delivery.
Note in general that the suspension fork must give in a little even when
you are just sitting on the bicycle – this is the so-called negative spring
travel or sag. If you ride over a pothole the spring is decompressed
c
and the suspension fork compensates for the unevenness. If the air
pressure or the spring preload are too high, this effect is lost because
the suspension forks is already fully extended. This means that an im-
portant comfort and safety factor is lost if the tyre briefly loses contact
with the ground.
The suspension fork should yield by about 10-25 % of its total travel
under the rider's weight (d).
Attach a cable tie around one of the stanchion tubes and pull it tight
enough so that it can still be moved but does not move by itself.
d
Sit on the bicycle while wearing your typical clothing for riding (with a
full backpack, if applicable), take up your usual riding position and lean
against a fixed object (railings, wall, etc.) so that you do not fall over.
Push the cable tie downwards against the dust seal at the lower tube
and get off the bicycle so that the fork does not compress any more.
76
(a)
and many city bikes and pedelecs
(c)
differ in their types of spring elements and damp-
Suspension fork manufacturers normally include instruc-
tions with their deliveries. Read them carefully before
changing any settings or doing any maintenance work on
your suspension fork. You can find the instruction of the
suspension fork manufacturer on the enclosed CD.
The distance between the cable tie and the dust seal is the negative
spring travel, or sag. Compare it against the total spring travel (as spec-
(b)
are
ified by the manufacturer) to determine whether the suspension should
be set to be harder or softer.
With most suspension forks with coil springs or elastomers the springs
can be adjusted and pretensioned within tight limits by turning a knob at
the top of the fork crown. If that is not possible and the desired negative
spring travel ("sag") cannot be set, the coil springs or elastomers must
be replaced by harder or softer examples. When replacing any parts be
sure to only use parts that bear the appropriate mark and, to be on the
safe side, original spare parts. Your WHEELER bicycle dealer will be
pleased to help you.
With pneumatic suspension forks the hardness of the spring is set by
the air pressure in the fork. The pressure must be set before the first
ride by means of a special high-pressure pump
and modified later as required due to changes in the weight of the
rider and/or load. Note the appropriate setting values and check them
subsequently at regular intervals. Always follow the recommendations
of the manufacturer and never exceed the maximum air pressure for
the suspension fork.
Always make a test ride after each change to the settings (f+g). Check
afterwards the position of the cable tie. Its distance from the dust seal
is the maximum spring travel that you have used. If the cable tie has
been moved by even a few millimetres, then the setting of the forks is
too hard. Reduce the pressure, or, in the case of coil springs, the spring
preload. If that brings no improvement then replace the springs.
If the cable tie has shifted over the entire length of the tube or if the fork
audibly "bottoms out" and hits the top repeatedly when riding off road
or on bad roads, then the setting of the springs is too soft. In this case
the spring preload/the pressure must be increased. If the adjustment
range of the coil spring is too small, have it replaced by your WHEELER
bicycle dealer.
G
Suspension forks are designed in a way to absorb shocks.
If the fork is too rigid and jammed, the terrain-induced
shocks pass directly into the frame without any damp-
ing. The frame is normally not designed to withstand such
undamped stresses. If your suspension fork has a lockout
mechanism (h), do not activate the lockout function when
riding in rough terrain, but only when riding over smooth
terrain (roads, field tracks).
(e)
with pressure gauge
e
f
f
g
h
77
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