Pontiac FIREBIRD 1972 Service Manual page 499

1972 PONTIAC SERVICE MANUAL
The piston is formed from steel, precision ground and
nickle-chrome plated, giving it a very hard and durable
surface. The use of abrasives or any attempt to re-machine
the piston will destroy the plating.
The machined caliper casting has two mounting holes at
each end of the caliper. The holes in the inboard ears are
larger in diameter than the holes in the outboard ears.
Sleeves and rubber bushings are assembled through the
two large holes in the inboard ears.
The caliper on A and G Series models is attached to a
support bracket mounted on the suspension. Bolts are
inserted through the sleeves, support bracket, under the
ears on the inboard shoe and through the outboard ears
on the caliper. The bolt threads engage tapped holes in the
support bracket and the bolt heads are tightened against
the ends of the sleeves. The caliper on
B,
F and
X
Series
mounts directly to an integral one piece steering knuckle
and brake caliper support (Fig. 5E-18). There is, therefore,
no separate mounting braket on these models. The caliper
is free to slide on the sleeves at the inboard ears and on
the bolt at the outboard ears.
The shoe and lining assemblies are constructed of a
stamped metal shoe with riveted lining.
INBOAR0 SHOE
OUTBOlRO SHOE
The rotor is a cast iron ventilated type with two machined
braking surfaces separated by fins.
OPERATION
The Significant feature of the single piston caliper operat-
ion is that it is free to slide on the two mounting bolts
which thread into the support bracket. Lining wear is
automatically compensated for by this sliding caliper fea-
ture. Fig. 5E-2 shows a simplified cross section of the
caliper, with both new and worn linings, and the forces at
work when the brakes are applied.
Upon application of the brakes, pressure is exerted equally
against the bottom of the piston and the bottom of the
piston bore. The pressure applied to the piston is transmit-
ted to the inboard shoe and lining, forcing the lining
against the inboard rotor surface. The pressure applied to
the bottom of the piston bore forces the caliper to slide or
move on the mounting bolts toward the inboard side, or
toward the car. Since the caliper is one piece, this move-
ment toward the car causes the outboard section of the
caliper to apply pressure against the back of the outboard
shoe and lining assembly, forcing the lining against the
outboard rotor surface.
NEW
"
WORN
Fig. 5E-1 Disc Brake Assembly
Fig. 5E-2 Simplified Single-Piston Disc Brake