Brakes - Volvo 164 Owner's Manual

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 operates mechanically
via the booster cylinder, this increasing the
pedal force about three times. The brake
pressure is transmitted hydraulically from
the master cylinder through the brake to
the wheel cylinders. The pistons in these
are then pressed outwards and apply the
brake pads. The pressure lines to the rear
wheel brakes are provided with a reducer
38
valve which prevents the rear wheels from
l ocking before the front wheels. The prin-
ciple of the two-circuit system is that both
the front wheels are connected to one rear
wheel, that is, should there be a failure
i n one of the circuits, there is always
braking power on both front wheels and
the other rear wheel. So at normal pedal
pressure the braking effect of one of the
circuits is 50 % ,
but when pedal pressure
i s increased, about 80 % of the full brak-
i ng power can be obtained in the one
circuit. This provides maximum safety and
prevents lateral dragging and rear-end
l urching. With the engine stopped, the
booster assists the braking a further two
or three times after which the pedal pres-
sure must be increased about three times
as much in order to obtain a braking pow-
er corresponding to the braking power
available with the engine running. The
parking brake 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 parking
brake.