BMW 645Ci Coupe 2004 User Manual

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103

road surface. This phenomenon is referred
to as hydroplaning, and is characterized
by a partial or complete loss of contact
between the tires and the road surface, ulti-
mately undermining your ability to steer
and brake the vehicle.

The risk of hydroplaning increases as the
tread depth of the tires decreases, also
refer to Tire tread on page

167

Driving through water

Do not drive through water on the
road if it is deeper than 1 ft/30 cm,

and then only at walking speed at the most.
Otherwise, the vehicle's engine, the electri-
cal systems and the transmission may be
damaged.

Braking safely

Your BMW is equipped with ABS as stan-
dard. The best way to achieve optimized
braking response from the ABS is to apply
maximum pressure to the brake pedal in
situations where this is required: panic
stops. Since the vehicle maintains steering
responsiveness, you can nevertheless
avoid possible obstacles with a minimum
of steering effort.

Pulsation at the brake pedal combines with
sounds from the hydraulic circuits to indi-
cate to the driver that ABS is in its active
mode.

Do not drive with your foot resting on
the brake pedal. Even light but con-

sistent pedal pressure can lead to high
temperatures, brake wear and possibly
even brake failure.

Driving in wet conditions

While driving in wet conditions and in
heavy rain, it is a good idea to apply light
pressure to the brake pedal every few
miles. Monitor traffic conditions to ensure
that this maneuver does not endanger
other road users. The heat generated in this
process helps dry the pads and rotors to
ensure that full braking efficiency will then
be available when you need it.

Hills

To prevent overheating and thus
reduced efficiency of the brake sys-

tem, downshift to a gear in which only min-
imal brake applications are needed when
descending long or steep downhill
stretches. Even light but consistent pedal
pressure can lead to high temperatures,
brake wear and possibly even brake fail-
ure.

You can further enhance the engine's brak-
ing effect by selecting a lower gear in the
automatic transmission's manual mode,
downshifting as far as first gear on
extremely steep stretches, refer to
page

. This strategy helps you avoid

placing excessive loads on the brake sys-
tem.

Never drive with the clutch pressed
or allow the vehicle to coast with the

transmission in Neutral – or with the engine
switched off – there is no engine braking
when the transmission is in Neutral, and no
power assist for brakes and steering when
the engine is not running.
Never allow floor mats, carpets or any other
objects to protrude into the area around the
accelerator and brake pedals and obstruct
their movement.

Corrosion on brake rotors

When the vehicle is driven only occasion-
ally, during extended periods when the
vehicle is not used at all, and in operating
conditions where brake applications are
less frequent, there is an increased ten-
dency for corrosion to form on rotors, while
contaminants accumulate on the brake
pads. This occurs because the minimum
pressure which must be exerted by the
pads during brake applications to clean the
rotors is not reached.

Should corrosion form on the brake rotors,
the brakes will tend to respond with a pul-
sating effect that even extended applica-
tion will fail to cure.

This manual is related to the following products:

645Ci Convertible 2004