Bendix Commercial Vehicle Systems AUTO SLACK ADJUSTER SERVICE MANUAL - Manual (Page 12)

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1 2 3 4 5 6 7 8 9
A
(Fully Retracted)
C
(80-90 PSI Brake Application)
B
(Drum Contact Using a Lever)
Free Stroke = B minus A
Applied Stroke = C minus A
AX011
Adjust the Self Adjusting Brake Adjuster
Free Stroke Adjustment
1. With air chamber fully retracted, measure distance from
face of air chamber to centerline of clevis pin. Record
exact measurement as dimension A.
2. Use a lever to move the brake adjuster until brake shoes
contact the drum.
3. Measure the distance between face of air chamber and
centerline of clevis pin. Record distance as dimension B.
4. Subtract dimension A from dimension B. The difference
is free stroke. Allowable free stroke is a minimum of 3/8"
stroke.
5. Remove lever and check that brakes are not dragging:
• Spin wheel end assembly by hand
• Tap drum lightly with a hammer, listening for a sharp
ringing sound
If brake drag is noted, back off brake adjuster and recheck free
stroke.
Note: A properly working self adjusting brake adjuster does not
require manual adjustment while in service.
NOTE: A properly working Automatic Slack Adjuster does not
require manual adjustment while in service. The manual adjuster
hex is intended for use during adjuster installation and brake
overhaul.
WARNING: Automatic slack adjusters should not be repeatedly
adjusted to correct excessive in service pushrod stroke,
because this condition indicates that a problem exists with the
automatic adjuster, with the installation of the adjuster or with
related foundation brake components which manual adjustment
will not correct.
Applied Stroke Adjustment
1. Apply and hold an 80-90 psi brake application.
2. Measure distance between face of air chamber and clevis
pin centerline. Record distance as dimension C.
3. Subtract dimension A from dimension C. The difference is
applied stroke. Compare applied stroke to maximum value
in table below.
4. If applied stroke equals or exceeds maximum applied
stroke shown, adjust brakes. If less than the maximum,
no adjustment is required.
Figure 18 Stroke Measurements
Installation
80 - 90 PSI
Air Chamber Maximum Desired
Size Applied Free
Stroke Stroke
Type 30" Long Stroke 2.5" 3/8" to 5/8"
Type 30" 2" (Without Drag)
Type 24" 1-3/4"
Type 24" (w/ 2-1/2" 2"
extended stroke)
Type 24 (w/3" extended stroke)
2.5"
Type 20" and 16" 1-3/4" 3/8" to 1/2"
Type 12" 1-3/8" 3/8" to 1/2"