Brake System Preventive Maintenance
– 152 – Y53-6008
Medium Duty (R10/06)
WARNING! Manual adjustment of automatic
slack adjusters is a dangerous practice that
could have serious consequences. It gives
the operator a false sense of security about
the effectiveness of the brakes. Contact the
Service Department at your dealership if the
stroke exceeds the above specifications. A
stroke exceeding these values may indicate a
problem with the slack adjuster or the brake
foundation.
• If the pushrod travel reaches the above specifications,
check the slack adjuster installation. Inspect brake
adjuster and anchor bracket for damage. The anchor
bracket should be tight.
• With the air system at 100 psi (690 kPa) or more, apply
the brake.
If adjustment is necessary and the slack adjuster is working,
the adjusting hex nut will rotate during the chamber return
stroke. Installing a wrench on the hex nut will make this eas-
ier to see. On each stroke after the first, the amount of adjust-
ment and chamber travel will be less.
Measuring Pushrod Travel
Table 5 Brake Adjuster Stroke
80–90 PSI (552 – 621 KPA) BRAKE APPLICATION
AIR CHAMBER
TYPE (Size)
BRAKE
PUSHROD TRAVEL
(Applied Stroke)
20 Front 1 to 1–3/4 in. (25–44mm)
30 Rear 1–1/4 to 2 in. (32–51mm)
SLACK
ADJUSTER
BRAKE
CHAMBER
PUSHROD
01830
“APPLIED STROKE”
