V-Brakes; Functional Check; Power Modulator - BMW Mountain Bike Enduro Owner's Manual

Ensure that the brake pads are absolutely free of wax, grease
and oil.
Have your rims regularly inspected and measured at a bicycle
specialist shop of your trust (a).
Brake cables that are damaged (b), e.g. frayed, should be
replaced immediately, as they can otherwise fail in a critical
moment, possibly causing an accident.

5.2.1 V-Brakes.

Common V-brake designs have two brake arms mounted separately
on either side of the rim. When actuating the brake lever, both arms are
tightened by the cable, the pads touch the rim.

5.2.1.1 Functional check.

Check whether the brake pads are accurately aligned with the rims and
still sufficiently thick. You can judge the wear of the brake pads by the
appearance of the grooves. If the pads are worn down to the bottom of
the grooves, it is time to replace them.
a b
The brake pads must hit the rim simultaneously, first touching it with the
front portion of their surface. At the moment of first contact the rear por-
tion of the pads should be a millimetre away from the rim. Viewed from
the top the brake pads form a "V" with the trough pointing to the front
(c). This V-shaped setting prevents the brakes from screeching when
applied.
The brake lever must always remain clear of the handlebars. You should
not even be able to pull them all the way to the handlebars in the event of
an emergency stop.
Only a successful passing of all these points will ensure a correctly
adjusted brake.
Adjusting the position of the brake pads relative to the rims
requires a considerable degree of skill. Replacing and adjusting
the brake pads is a job best left to a bicycle specialist shop of
your trust.
5.2.1.2 power modulator (d).
Some V-brakes are fitted with a power modulator that acts as brake
force control during braking hereby limiting the brake force.
This device is intended to prevent overbraking and a blocking of the
front wheel.
c
d
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