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IM
Saab
Front Disc
Brake Service
Most of us consider disc brake service to be a fair
ly straightforward repair procedure. Resurface or
replace the rotors, clean the calipers, stuff in a new
set of pads and hardware, pump the brakes, and off
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you go. No big deal, right?
But what happens when the customer who owns
this Saab 900 model returns complaining about a
severe caliper clunk that didn't disappear with new
pads (especially when backing and braking at the
same time)? Or maybe there's still some brake shud
der he wrongly assumed would disappear with a sim
ple pad replacement.
The front discs on this Saab also contain the hand
brake mechanisms, and will require a little more ex
pertise on your part than you might expect. Knowing
a few tricks and recognizing excessive wear at certain
key points can save you the embarrassment of explain
ing away these annoying problems.
The fact that the hand brake mechanisms are in
cluded in these calipers complicates things only if
they stick, bind, or are improperly adjusted. As a
result, we include more than average coverage of the
hand brake and its hardware.
To start with, we suggest that all cleaning, inspec
tion, and especially lubrication be done before rotor
resurfacing or replacement. That way you won't be
slopping anti-seize all over the clean rotor surface and
brake pads.
In addition, when you're all finished with your
reline, don't just hop in the car and pump up the pads.
First pull the hand brake lever up six clicks. Then
pump the brakes to correctly position the pads before
releasing the lever. This will properly set the initial
pad-to-rotor clearance.
—By Ralph Birnbaum
Before you start, we wanted to take a moment to show
you where NOT to grab the brake/knuckle assembly
when turning it from side to side. Too much pressure
on the rotor splash shield can distort it and cause it
to rub on the rotor and make a scraping noise.
If the pads are worn thin, the primary piston (the one
next to the rotor) will be screwed out pretty far. Before
exercising the caliper, use Saab special tool 8996043
or equivalent to partially screw the piston in. Turn it
clockwise and be careful not to damage the caliper
boot.
Spray the big U-pin with penetrating oil and drive the
pin in slightly. This will force the penetrant into the
caliper holes, and remove the tension from the retainer
clip (black arrow). Now pry the U-clip out with a small
bar or screwdriver. The anti-rattle clip will fall out
(white arrow).
Here are the brake pistons removed. See how they
screw apart to compensate for pad wear? You want to
screw that primary piston (left) inward enough to keep
it from popping out of its seal when you begin exer
cising the caliper in the next step. Always check for
torn boots or rusted pistons.
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Now free the yoke by alternately prying between the
Don't just beat on the yoke to free the slides between
yoke and rotor (black arrow) and primary piston and
rotor (white arrow) to exercise the assembly. As you
pry the yoke outward, you'll see the primary piston
move toward the rotor. Once the yoke is fully outboard,
finish screwing in the primary piston.
the piston assembly and yoke. If the secondary piston
sticks to the yoke, you'll pop its seal. Pry as shown
as you tap the yoke inboard. This will free the second
ary piston and help free a sticking hand brake arm at
the same time.
These slides allow the caliper frame and pads to float
on the piston housing. The fit between the yoke and
housing is critical to proper brake operation. It must
be clean and well lubed so it can slide. It must also
be tight enough not to knock and make noise.
Here's a worn yoke removed from the caliper assembly.
This one is badly grooved where it rides in the piston
housing. When this customer backed the car and braked
at the same time, the extra slop allowed the caliper
to shift and clunk. It's new caliper time for this car.
Now remove the big return spring on the hand brake
activator and work the hand brake lever out of the
secondary piston. There is a replaceable seal on the
shaft where it rides in the secondary piston that can
seize and stick on the lever shaft.
This small rubber tab on the hand brake cable dust
boot keeps the cable in the hand brake arm. You'll have
to push it away before disconnecting the cable. With
the cable removed, check for signs of a torn boot or
sticking cable. Don't push the cable in too far, however.
We'll explain why later.
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Here, we've removed the hand brake activator from the
caliper frame. Make sure the areas shown are clean and
burr free. Always wire brush and lubricate this arm
with an anti-seize compound before reinstalling it. We
don't want it to stick and keep the hand brake applied
all the time.
Here's a better look at the hand brake mechanism and
activator. The notch in the shaft fits into the notched
round disc. The lever rotates the disc against ball bear
ings. The balls climb those ramps in their recesses,
forcing the discs apart. Again, we don't want the shaft
With the hand brake lever removed and the secondary
piston free of the yoke, clean and lubricate the second
ary piston slot and the yoke. Also clean and lubricate
the slot in the yoke where the hand brake lever rides.
Reinstall the hand brake lever before tapping the yoke
back on the secondary piston.
Now reinstall the brake arm return spring. Here's what
it should look like, just in case you forgot. Before you
reinstall the cable, check the arm for free movement,
making sure it returns to the fully off position without
sticking or binding. This is very important.
When reinstalling the hand brake cable in the arm,
it is very important that the hand brake cable isn't
either stuck "on" or adjusted up too tightly. There
should be a slight amount of free play between the
cable and arm (indicated by the feeler gauge), or the
brake will stay partially applied.
Remember we told you not to push the hand brake
cables in too far? If you do, you can push the shouldered
adjusting nut out of its hole in the hand brake and it'll
catch. You'll have to go inside the car, push the seat
forward and remove the inspection covers on the con
sole to reinsert them.
sticking in the "on" position.
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After reinserting the shouldered adjusting nut as
shown, double check to make sure that you have that
small amount of free play at the brake arm. The ad
juster for the right caliper is on the left side of the con
sole. The adjuster for the left caliper is on the right.
Don't be fooled.
Here are a couple quick tips on rotor R and R. Tired
After removing the rotors for resurfacing, clean the
drive hub/rotor locating surfaces. Remove all ac
out condition at the rotor braking face. A wire brush
and some sand paper, followed up by some anti-seize
compound, will do the trick.
The U-pin should have a slight bend in it of approx
imately 20 degrees. This puts tension on the pads and
caliper frame to further minimize any tendency for the
calipers to chuck and knock. Heat and normal use can
straighten the pins, however, contributing to caliper
knock.
Just in case this is your first run at these, you might
forget how this spring clip was positioned. This spring
goes in front of the U-clip and helps absorb some of
the U-clip vibration. It must snap in the center hole
in the yoke and then snap over the U-clip to be
effective.
After installing the U-shaped pad retainer clip, insert
the lock pin. Then pull the U-clip back against the
lock pin. This will tension the U-clip against the pin
to hold it. It will also give you a little room to drive
the U-clip in for the next brake job. Reinstall the antirattle clip.
cumulations of rust or corrosion, or you'll get a run
of breaking tips on your impact driver trying to remove
these Phillips® head screws? Place the ball end of
your ball peen on the screw head and rap it with a
brass hammer. This will loosen the screw. Then finish
removing it with your impact driver.