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Peterbilt Medium Duty Truck Owner's Manual - Peterbilt Motors

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Preventive Maintenance<br />

Measuring Pushrod Travel<br />

Table 4<br />

SLACK<br />

ADJUSTER<br />

Brake Adjuster Stroke<br />

80–90 PSI (552 – 621 KPA) BRAKE APPLICATION<br />

AIR CHAMBER<br />

TYPE (Size)<br />

BRAKE<br />

BRAKE<br />

CHAMBER<br />

“APPLIED STROKE”<br />

PUSHROD<br />

01830<br />

PUSHROD TRAVEL<br />

(Applied Stroke)<br />

20 Front 1 to 1–3/4 in. (25–44mm)<br />

30 Rear 1–1/4 to 2 in. (32–51mm)<br />

Brake System<br />

WARNING! <strong>Manual</strong> adjustment of automatic<br />

slack adjusters is a dangerous practice that<br />

could result in an accident involving death or<br />

injury. It gives the operator a false sense of<br />

security about the effectiveness of the brakes.<br />

Contact the Service Department at your dealership<br />

if the stroke exceeds the above specifications.<br />

A stroke exceeding these values may<br />

indicate a problem with the slack adjuster or the<br />

brake foundation.<br />

• If the pushrod travel reaches the above specifications,<br />

check the slack adjuster installation. Inspect brake<br />

adjuster and anchor bracket for damage. The anchor<br />

bracket should be tight.<br />

• With the air system at 100 psi (690 kPa) or more, apply<br />

the brake.<br />

If adjustment is necessary and the slack adjuster is working,<br />

the adjusting hex nut will rotate during the chamber return<br />

stroke. Installing a wrench on the hex nut will make this easier<br />

to see. On each stroke after the first, the amount of adjustment<br />

and chamber travel will be less.<br />

<strong>Medium</strong> <strong>Duty</strong> (R05/09) Y53-6027 – 187 –

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