Rim Trueness, Spoke Tension - BMW Mountain Bike Enduro Owner's Manual

Tyres with car valves can conveniently be inflated at car filling stations
with a compressed air dispenser. The same applies to Presta valves
fitted with a special adapter. A compressed air dispenser must be used
very carefully as you may otherwise overinflate the tyre and make it
burst. To let out air, press the needle in the centre of the car valve or the
knurled nut of the Presta valve using e.g. a spanner/key.
Hand pumps are often unsuitable for inflating tyres to high pressures. A
better choice is a foot-operated or a track pump equipped with a pres-
sure gauge (b).
Always ride your bicycle with the prescribed tyre pressure and
check the pressure at regular intervals, at least once a week.
Replace tyres with a worn tread or with brittle or frayed sides. Dampness
and dirt penetrating the tyre can cause damage to its inner structure.
The inner tube might burst. Risk of accident!
Observe the maximum pressure value of the rim. The pressure
is dependent on the tyre width! You will find the values in the
enclosed manuals of the rim manufacturers.
a
40
b

7.2 Rim Trueness, Spoke Tension.

To obtain true running of the wheel, the tension exerted by the spokes
has to be distributed evenly around the rim (c). 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 unbalanced and the
wheel will no longer run true. The functioning of your bicycle may even
be impaired before you notice the wobbling appearance of a wheel that
has gone out of true.
With rim brakes the sides of the rims also serve as braking surfaces. An
untrue wheel can impair your braking power. It is therefore advisable to
check the wheels for trueness from time to time. For this purpose lift the
wheel off the ground and spin it with your hand. Watch the gap between
the rim and the brake pads. If the gap varies by more than a millimetre,
you should ask at a bicycle specialist shop of your trust to true up the
wheel (d).
Do not ride with untrue wheels. In the case of extreme side-to-
side wobbles, the brake pads of rim brakes can miss the rim
and get caught in the spokes! This normally instantly jams the
wheel and throws you off your bicycle.
Loose spokes must be tightened at once. Otherwise the load
on the other spokes and the rim will increase.
Truing (retruing) wheels is a difficult job which you should
definitely leave to a mechanic of a bicycle specialist shop of
your trust!
c
d