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68
BRAKE SYSTEM
RIM BRAKES
ROAD BIKE RIM BRAKES
Brakes – how they work and what to do about wear
Actuating the hand lever on the handlebar causes a
stationary brake pad to be pressed against a rotating
braking surface, and the resulting friction slows down
the wheel. The rate of deceleration is not only deter-
mined by the force with which the brake pad is pressed
against the braking surface, but also to a decisive de-
gree by the coefficient of friction, which depends on
the two materials that are rubbed against each other.
When water, dirt or oil gets in contact with one of the
engaging surfaces, this changes the coefficient of
friction. This is why brakes respond at a slight delay
and less powerfully in wet weather. The friction gen-
erated by braking causes wear to the brake pads as
well as to the rims! Frequent rides in the rain hasten
wear on both engaging surfaces.
Rims are provided with wear indicators, i.e. grooves
or circular indentations. If the rim is worn down to the
point where the grooves or indentations are no longer
visible, they need to be replaced. Once the abrasion
of the rim has reached a certain critical point, the rim
may break under the tyre pressure. This can make the
wheel jam or the inner tube burst, both of which can
cause an accident!
We advise you to have the remaining thickness of the
rims checked at the latest when you are through your
second set of brake pads.
When replacing brake pads, be sure to
i
only use marked original brake pads
matching your rim.
Ensure that braking surfaces are abso-
!
lutely free of wax, grease and oil. Ask a
skilled mechanic to examine the rims at the latest
when you are through your second set of brake
pads. Worn down rims may make the inner tube
burst, thus leading to a crash! In order to maintain
their effectiveness brakes need to be checked
and readjusted from time to time.
Brake pads with worn down wear indicators, i.e. grooves, (bottom
brake pad) must be replaced
Have your rims regularly inspected and measured
Carbon rims require special brake pads according to the instructions
of the wheel manufacturer
Damaged brake cables that are for exam-
ple frayed should be replaced immediate-
ly, as they can otherwise fail in a critical moment,
possibly causing a crash.
Checking and readjusting road bike brakes
With side-pull brakes the brake arms are suspended
from a common point, thus forming an integral sys-
tem. When actuating the brake lever, both arms are
tightened by the cable, the pads touch the rim.
Checking the brake system
Check whether the brake pads are accurately
aligned with the rims and still sufficiently thick (see
chapter "The brake system").
Do both brake arms contact the rim simultaneous-
ly when actuating the brake levers? Do you get a
clear-cut braking response when you pull the brake
lever hard, and does the lever remain clear of the
handlebars no matter how hard you pull?
An accurate adjustment of the brake is achieved,
when your brake system has passed on all of the
above points.
Vertical adjustment of the brake pads
Release the fastening bolt of the brake pad by one
to two complete turns at the most.
Push the brake pad to the correct height and align
it according to the rim before re-tightening the fas-
tening bolt to the specified torque.
Manufacturers of brakes deliver their
i
products with detailed operating instruc-
tions. Be sure to read these operating instruc-
tions carefully before you dismount a wheel or do
any maintenance work.
RIM BRAKES
BRAKE SYSTEM
69
The brake pad must hit the rim accurately
To adjust the height of the brake pads tighten the bolt to the pre-
scribed torque
When replacing any parts be sure to only
i
use original spare parts!
After the readjustment do a brake test in
standing. Make sure the brake pads en-
gage fully with the rim when you pull them hard
without touching the tyre. Furthermore you
should not be able to pull the brake levers all the
way to the handlebars. Otherwise the brake might
fail or the tyre sustain damage, thus causing an
accident.
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