Air Brake Manual

· Make a chalk mark where the push rods enter the
brake chambers.
· Reapply spring parking brakes and measure the
distance from the brake chamber to the chalk
mark. Ensure the slack (push rod travel) is within
1/2 - 3/4 inches or within manufacturer’s
specifications and the angle between the slack
adjuster and push rod is 90° or as close as
practical. If not, then a brake adjustment is
required.
The following are recommended adjustment steps
for S-cam brakes with manual slack adjusters.
· Ensure vehicle is secure and wheels blocked,
release the spring parking brake.
· Verify reservoirs are at full pressure.
· Use a wrench to disengage the external locking
device (if so equipped) from the adjustment bolt of
the slack adjuster.
· Turn the adjustment bolt until the brake lining
contacts the brake drum. If possible, visually
check to see that the brake linings are in contact
with the brake drum.
· 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. Check that the push rod free travel is now
between 1/2 to 3/4 inches, or within
manufacturer’s specifications.
Brake Test
· Reapply the spring parking brake, remove wheel
blocks.
· Gently tug against the spring parking brakes in
low gear, it should hold the vehicle.
· Release the spring parking brakes.
· Move vehicle ahead slowly and make a service
brake application to check brake response.
Combination Unit
When upgrading your driver’s licence from single to
combination vehicles with air brakes, you will be
required to satisfactorily demonstrate the pre-trip air
brake inspection for combination vehicles.
The pre-trip air brake inspection should be completed
within 30 minutes. Failure to complete the test within
30 minutes may result in the test being discontinued.
Practical examination will be conducted in either the
metric or imperial systems of measurement,
whichever coincides with the equipment being
operated.
Vehicle Secure
· Set the spring parking brake on tractor and trailer.
· Block the wheels; the vehicle should be on level
ground if possible.
· Check that the compressor is secure.
· Check the drive belt and pulleys for wear, cracking,
slippage and tension (if equipped).
· Drain all reservoirs completely on the tractor
(wet/supply reservoirs first) then the trailer.
When reservoirs are empty close the drain valves.
“For testing purposes only, the applicant will not be
required to manually drain the reservoirs. Instead,
the applicant will verbally explain the steps that they
would follow when draining the reservoirs and then
fan the brake pedal to empty the reservoir.”
· Check brake chambers, air lines and slack adjusters
for security and wear.
· Ensure the air brake glad hands and trailer electrical
cord is connected properly.
Compressor and Warning Devices Check
· Start the engine and run at fast idle to build up air
pressure.
· Warning device(s) must operate to 55 psi or higher.
· Ensure reservoir air pressure builds from 50 to 90 psi
within three minutes.
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