Brakes - Volvo 164 Instruction Book

TECHNICAL DESCRIPTION

BRAKES

The brake system is of the two-circuit type
with disc brakes all round. The system is
provided with a tandem-type master cylin-
der and a directly-operating booster cylin-
der. When the brake pedal is depressed,
the master cylinder is operated mechani-
cally via the booster cylinder, this boost-
i ng the pedal force about four times. The
brake pressure is transmitted hydraulically
from the master cylinder through the brake
l ines to the wheel cylinders. The pistons in
these are then pressed outwards and ope-
rate the brake pads. The pressure lines to
32
the rear wheel brakes are provided with a
reducer valve for each circuit to prevent
l ocking of the car wheels.
The principle of the two-circuit system is
that both the front wheels are connected
to one rear wheel, that is, should there be a
failure in one of the circuits, there is al-
ways braking power on both front wheels
and the other rear wheel. At normal pedal
pressure the braking effect of each of the
circuits is 50 % but when pedal pressure
,
i s increased, about 80 % of the full braking
power can be obtained in the one circuit.
This provides maximum safety and pre-
vents lateral dragging and rear-end lurch-
i ng. With the engine stopped, the booster
assists the braking a further 2 or 3 times
after which the pedal pressure must be
i ncreased about four times in order to
obtain a braking power corresponding to
the braking power available with the en-
gine running.
The handbrake operates the rear wheels
mechanically as the brake discs have also
been designed as brake drums in order to
i ncorporate the shoes for the handbrake.