Porsche 928 S 1984 Owner's Manual page 25

Brakes
Functioning of brake system
Your Porsche is equipped with a power as-
sisted hydraulic dual circuit brake system with
disc brakes at the front and at the rear. Both
circuits function independently.
In the unlikely event of hydraulic failure of
one circuit, push the brake pedal down
firmly and hold it in that position. A mechan-
ical linkage activates the second circuit,
and you will be able to bring the vehicle to
a safe stop.
WARNING
Failure of one brake circuit will impair the
braking capability resulting in an increased
stopping distance.
If one brake circuit has failed, the other will still
operate. However, you will notice an increased
pedal travel when you step on the brake.
Should you encounter such experience, bring
your vehicle safely to a full stop.
Avoid driving the vehicle and have it towed
to the nearest authorized Porsche dealer.
24
Brake pedal
WARNING
• The movement of the brake pedal must
never be obstructed by a floor mat or
any other object. In case one of the two
brake circuits fails, increased pedal tra-
vel is required to bring your vehicle to a
full stop.
• Make sure that the size of your floor mat
does not hamper the movements of
either brake, clutch or accelerator ped-
als in any way.
• Secure the floor mat against sliding into
positions that could interfere with the
safe operation of your vehicle.
• Do not "ride the brakes" by resting your
foot on the pedal when not intending to
brake. Overheating and wear of the
brakes is the result.
• Before descending a steep grade, re-
duce speed and shift transmission into
a lower gear or driving position to con-
trol speed. Do not ride the brakes or hold
pedal down too long or too often. This
could cause the brakes to get hot and
not function properly.
With correctly adjusted brakes, and a correct-
ly working brake system, the pedal travel to
the point of brake actuation should be 1 -3/16"
to 1 -9/16" or 30 to 40 mm. Whenever the brake
pedal travel exceeds this distance, have the
brake system checked.
Keep in mind that the braking distance in-
creases very rapidly as the speed increases.
At 60 mph or 100 km/h, for example, it is not
twice but four times longer than at 30 mph or
50 km/h. Tire traction is also less effective
when the roads are wet or slippery. Therefore,
always maintain a safe distance from the car
in front of you.
Moisture or road salt on brakes affects
braking
WARNING
Driving through water may reduce the trac-
tion. Moisture on brakes from road water
or car wash or coating of road salt may af-
fect braking efficiency. Cautiously apply
brakes for a test. When the vehicle is driven
on salted roads for extended periods, the
brakes should be hosed down thoroughly
about every 2 weeks. An automatic car-
wash facility cannot do this job properly.
Brakes will dry after a few cautious brake
applications.