Disc Brakes - BMW 840Ci Owner's Handbook Manual

Disc brakes

130
Disc brakes offer maximum braking
efficiency, responsive control of brak-
ing force and the ability to resist
severe loads.
If the car is not driven very far, is
parked out of use for lengthy periods
or is mostly driven very gently, corro-
sion of the brake discs and contami-
nation of the pads may unfortunately
be encouraged, since the minimum
pressures between pad and disc
which are needed to obtain an auto-
matic cleaning action are seldom
reached.
When the brakes are applied, cor-
roded discs tend to judder, and even
lengthy brake applications usually fail
to eliminate this effect entirely.
a
Use only brake pads approved
by BMW, or else the car's operating
permit will be invalidated.c
Driving hints
In damp weather or heavy rain it is
advisable to apply the brakes with
light pedal pressure every few kilome-
tres. When doing so, make sure that
no other road-user is endangered.
This will generate sufficient heat to dry
out the discs and pads.
It is a well-known fact that the best
braking effect is obtained not with-
locked wheels but with wheels that
are still just rotating. ABS maintains
this state of affairs automatically. If an
ABS malfunction occurs, the driver
should adopt the cadence braking
principle if possible (see Page 122).
To avoid any risk of brake fade when
descending long or steep hills, select
the gear which calls for a minimum
amount of braking (or shift the auto-
matic transmission down to an equi-
valent speed stage).
Engine braking can be enhanced by
shifting to a lower gear, if necessary
as far as first gear or selector lever
position 2.
If engine braking alone is insufficient,
do not apply the brakes for too long
with only slight or moderate force.
Instead, it is better to brake the car
quite hard (providing that the road
behind you is clear) so that your
speed is reduced noticeably, and to
repeat this process at brief intervals
as necessary. The cooling-down
phases between these brake applica-
tions should avoid overheating and
maintain full braking efficiency.
a
Never hold the clutch pedal
down, move the gearbox or automatic
transmission into neutral or – an even
more dangerous practice – switch off
the engine while the car is in motion.
Engine braking is lost in neutral, and
there is no brake servo effect when
the engine is stopped. Make sure that
the full travel of the brake, clutch and
accelerator pedals is never obstructed
by the floor carpet, loose mats or any
other items.c
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