Air Brake Manual

S-cam Brake Adjustment with Manual Slack Adjuster
· Ensure vehicle is secure and wheels blocked,
release the parking brake.
· Verify system is at full pressure.
· Use a proper wrench to disengage the external
locking device (if so equipped) from the adjustment
bolt of the slack adjuster.
· Turn the adjustment bolt until the lining contacts the
drum and the adjustment bolt will not turn any
further. If possible, visually check to see that the
brake linings are in contact with the brake drum.
Pull or pry on the slack adjuster. There should be no
movement or free play. If there is free play, you have
turned the adjusting nut the wrong way.
· When turning the adjustment bolt on the slack
adjuster, the S-cam should turn in the same
direction as if a brake application were being
made.
· Back off the adjustment bolt about 1/4 to 1/2 of a
turn and ensure the locking device reengages.
· Now recheck slack adjuster travel. The travel
should now be between 1/2 to 3/4 inches free travel
while pulling on the linkage, or within
manufacturer’s specifications.
Note: Applicants conducting an air brake examination
will be required to satisfactorily adjust S-cam brakes
with manual slack adjusters.
The equipment required to adjust a brake must be
supplied by the applicant.
S-cam Brake with Automatic Slack Adjuster
Automatic slack adjusters adjust themselves during
brake applications to accommodate for brake lining
and drum wear. However, they must be checked
daily to ensure they are maintaining proper push rod
travel which normally is two inches when the brake
is applied. Normally two to four brake applications
of 80-100 psi per day will keep the brakes properly
adjusted, a driver may be required to consciously
make these applications when starting out for the
day or during the trip when possible. If they are
badly out of adjustment, a qualified mechanic should
inspect them. Adjusting automatic slack adjusters
by hand is not recommended unless you are
thoroughly trained on the proper adjustment
procedures as dictated by the manufacturer. If an
automatic slack adjuster requires adjusting by hand
the slack adjuster may not be working properly and
should be inspected or replaced by a qualified
mechanic as soon as possible.
Disc Brake Adjustment
There are a number of makes and models of air disc
brakes, each with a different adjustment procedure.
It is therefore recommended that you consult the
manufacturer’s manual for adjustment or service.
Wedge Brake Adjustment
Manual adjusters:
· Hoist or jack wheels off the ground.
· Remove dust cover from adjusting slots at two
places on each brake. On twin chamber units the
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