Installation
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.
Free Stroke = B minus A
Applied Stroke = C minus A
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.
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" |
| |||
Type 24" (w/ | 2" |
| ||
extended stroke) |
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| ||
Type 24 (w/3" extended stroke) | 2.5" |
| ||
|
|
| ||
Type 20" and 16" | 3/8" to 1/2" | |||
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|
| ||
Type 12" | 3/8" to 1/2" | |||
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A
(Fully Retracted)
B
(Drum Contact Using a Lever)
1
C
2 | 3 | 4 | 5 | 6 | 7 |
8
9 AX011
Figure 18 Stroke Measurements | 11 |
