Bendix Commercial Vehicle Systems MANUAL SLACK ADJUSTERS - Manual (Page 2)

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Using the Positive Lock Slack Adjuster Mechanism: (Fig. 1)
Wipe the adjusting screw nut and locking sleeve area clean.
Position wrench or socket over the adjusting screw and
disengage the locking sleeve by depressing the lock sleeve.
Make the necessary adjustment by turning the adjusting
screw with the locking sleeve depressed.
When adjustment is completed, the adjusting screw nut
should be positioned so the locking sleeve engages the
adjusting screw nut, thus locking the adjusting screw in
place. DO NOT ATTEMPT TO TURN THE ADJUSTING
SCREW WITHOUT FULLY DEPRESSING THE LOCK
SLEEVE.
Using the Ball Indent Slack Adjuster Mechanism: (Fig. 2)
Before proceeding with adjustment, measure distance from
top of lock screw head to slack adjuster body.
To adjust, back off lock screw (counter clockwise) and make
necessary adjustment by turning the adjusting screw. After
adjustment is complete, retighten lock screw, making certain
that lock ball is engaged on the plunger shaft. (Proper
engagement can be confirmed by checking the measurement
from the top of the lock screw head to the slack adjuster
body. It should be the same before and after the adjustment.)
PROCEDURE
Vehicle brakes should normally be adjusted using the vehicle
or brake manufacturer’s recommendations. If they are not
available, the following can be used:
1. Bring the vehicle to rest on a level surface and chock the
wheels.
2. Mechanically release (“cage”) the spring brakes.
BRAKE ADJUSTMENT CHECK
A. PREFERRED METHOD
Determine the brake chamber size. Make a 100 psi
application to the service brakes and measure the push rod
stroke. Using the chart (Fig. 3) compare the actual chamber
stroke to the recommended maximum stroke to determine
if brake adjustment is required.
B. ALTERNATE METHOD
Determine the slack adjuster arm length (Dim. A). Measure
push rod movement (stroke) by manually extending push
rod until brake shoes contact drum. Refer to chart (Fig. 4). If
Dim. “B” is greater than allowable stroke indicated brakes
need to be adjusted.
BRAKE ADJUSTMENT
A. PREFERRED METHOD
Raise the vehicle wheel that is to be adjusted off the ground
so that it turns freely. Turn the slack adjuster adjusting
mechanism until the brakes begin to drag. Adjustment is
then backed off until the wheel turns freely. This adjustment
method will result in the shortest possible actuator stroke
without the brakes dragging.
B. ALTERNATE METHOD
Regardless of the brake chamber size or the slack arm length
adjust the slack adjuster so that there is 3/8" travel of the
push rod when manually extended to contact the brake shoes
to the brake drum. After adjustment, check for brake drag
by gently striking the brake drum with a hammer. When the
brake shoes are away from the drum, a ringing sound will be
heard. A dull sound indicates brake drag and requires
readjustment until the drag is eliminated.
NOTE: If the brakes cannot be adjusted per the above
instructions inspect the foundation brake and drum
for worn or damaged components.
PREVENTIVE MAINTENANCE
Every month, 8000 miles or 300 operating hours; check push
rod travel. Stroke should be short as possible without brakes
dragging or chamber rod binding. Adjust if necessary.
Every six months, 500,000 miles or 1800 operating hours;
lubricate slack adjuster with chassis lube N.L.G.I. grade 1
or 2. Apply a sufficient amount of grease to completely fill
body cavity.
FIGURE 3
CLAMP RING TYPE CHAMBER DATA
(Dimensions in inches)
Max. Max. Stroke
Stroke at Which
Effective * With Brakes
Area Outside Max. Brakes Should Be
Type (Sq. In.) Diameter Stroke Adjusted Readjusted
6 6 4-1/2 1-5/8 Should 1-1/4
9 9 5-1/4 1-3/4 be as 1-3/8
12 12 5-11/16 1-3/4 short as 1-3/8
16 16 6-3/8 2-1/4 possible 1-3/4
20 20 6-25/32 2-1/4 without 1-3/4
24 24 7-7/32 2-1/4 brakes 1-3/4
30 30 8-3/32 2-1/2 dragging 2
36 36 9 3 2-1/4
*Dimensions listed do not include capscrew head projections
for rotochambers and bolt clamp projections for clamp type brake
chambers.
A
B
FIGURE 4
Slack Adj. Arm Length Push Rod Movement (stroke)
“A” Dim. (in.) “B” Dim. (in.)
5 1-1/2
5-1/2 1-1/4
6 1
6-1/2 3/4