Drum Brakes
- Park the vehicle on a level surface, shut down the engine, and set the parking brake. Chock the tires. Once the tires are chocked, release the parking brake.
- With the engine off, and 100 psi (690 kPa) of air tank pressure, have an assistant apply and hold an 80 to 90 psi (552 to 621 kPa) brake application.
- Check to see if the colored over-stroke band on each brake chamber pushrod is exposed.
- Measure the applied chamber stroke. See Table. for the proper stroke for the type of chamber being used. If the stroke is too short, the brakes may drag or will not fully apply. Check for improper operation or adjustment of the automatic slack adjuster. See of the 108SD and 114SD Workshop Manual for inspection and troubleshooting procedures.
- Check all of the foundation brake components for damage,
wear, and loose or missing parts. Repair as needed. See of the 108SD and 114SD Workshop
Manual for inspection, troubleshooting, and repair procedures.
Table 1, Brake Chamber Stroke Specifications
Chamber
Max Applied Stroke: inch (mm)
Manufacturer
Type 1
Size 2
Gunite
Standard Stroke
9
1-3/8 (35)
12
16
1-3/4 (45)
20
24
30
2 (51)
36 3
2-1/4 (57)
Long Stroke
16
2 (51)
20
24
24
2-1/2 (64)
30
Haldex
Standard Stroke
12
1-3/8 (35)
16
1-3/4 (44)
20
24
2-1/2-inch Extended Stroke
24
2 (51)
3-inch Extended Stroke
24
2-1/2 (64)
Standard Stroke
30
2 (51)
Long Stroke
30
2-1/2 (64)
Meritor
Standard Stroke
9
Less than 1-1/2 (38)
12
16
Less than 1-3/4 (44)
20
24
Less than 1-7/8 (48)
Long Stroke
24
Less than 2 (51)
Standard Stroke
30
- Long stroke design is indicated by a tag, or embossing, on the brake chamber.
- Specifications are relative to a brake application with 80 to 90 psi (550 to 620 kPa) air pressure in the brake chambers.
- If type 36 chamber is used, slack length should be less than 6 inches.
Table 1, Brake Chamber Stroke Specifications
Warning: Manually adjusting an automatic slack adjuster to bring the pushrod stroke within legal limits is likely masking a mechanical problem. Adjustment is not repairing. Before adjusting an automatic slack adjuster, troubleshoot the foundation brake system and inspect it for worn or damaged components. Improperly maintaining the vehicle braking system may lead to brake failure, resulting in property damage, personal injury, or death.