Merida E-bike - Bicycle Valves and Rim Trueness

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a
b
c
d
Valves
There are three valve types in general use on city and
trekking bikes:
1. Sclaverand or Presta valve (a) : This valve is nowa-
days used on almost all types of bikes. It is designed
to withstand extremely high pressures.
2. Schrader or American valve
(b) : This is an adapted
car tire valve.
3. Dunlop or Woods valve
(c) : the usual valve.
All valve types come with a plastic cap to protect them
from dirt.
The Schrader and Dunlop valves can be inflated with a
suitable pump directly after removing the protective cap.
With Presta valves you first have to undo the small
knurled nut a little and depress it carefully until air starts
to escape. Check the valve core is tightened and seated
in its stem, otherwise air may slowly leak out. Do not
forget to tighten by hand the valve nut after inflating.
Tires with Schrader valves can conveniently be inflated
at car filling stations with a compressed air dispenser.
The same applies to Dunlop and Presta valves fitted
with a special adapter. A compressed air dispenser must
be used very carefully in short bursts as you may other-
wise overinflate the tire and make it burst.
To let out air, press the needle in the center of the
Schrader valve or the knurled nut of the Presta valve
(d) .
In the case of the Dunlop valve unscrew the knurled nut
until air comes out of the valve. Retighten the knurled
nut subsequently. Normally, you have to inflate the tire
completely.
It can be hard to inflate tires to the necessary pressure by
using hand pumps. It is much easier with a track pump
equipped with a pressure gauge.
Rim trueness and spoke tension
For the true running of the wheel it is imperative that
the tension exerted by the spokes is distributed evenly
around the rim. If the tension of a single spoke changes,
e.g. as a result of riding fast over a kerb or of a loose
nipple, the tensile forces acting on the rim become un-
balanced and the wheel will no longer run true. The
functioning of your MERIDA bike may even be impaired
before you notice the wobbling appearance of a wheel
that has gone out of true.