Volvo 164 Owner's Manual - page 37
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
36
wheel brakes are provided with a reducer
valve which prevents the rear wheels from
locking 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 one of the circuits fail,
there is always braking power on both front
wheels and the other rear wheel. So at nor-
mal pedal pressure the braking effect of
one of the circuits is 50 %, but when pedal
pressure is increased, about 80 % of the
full braking 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 press-
ure must be increased about three times as
much in order to obtain a braking power
corresponding to the braking power avail-
able 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 incorporate the
shoes for the parking brake.