BENDIX SD-20-6608 User Manual
1
Bendix
®
A2LS
™
Hydraulic Drum Brakes w/Parking
SD-20-6608
FIGURE 1 - A2LS
™
AUTOMATIC ADJUSTING TWO LEADING SHOE DRUM BRAKE
WHEEL CYLINDER
WHEEL CYLINDER END
SHOE RETURN SPRING
GROMMETS
CAP SCREWS
SHOE HOLD-DOWN CLIP (NOT
FITTED TO EARLY BRAKES)
DIRT SHIELD
CROSS-OVER
PIPE
GASKET
EXPANDER END SHOE
RETURN SPRING
DESCRIPTION
The A2LS
™
drum brake is a hydraulically operated
duo-duplex brake with an automatic adjustment and parking
brake feature. The A2LS
brake feature. The A2LS
™
drum brake (automatic adjust,
two leading shoes) provides two leading shoes in either
direction of drum rotation and an automatic adjustment of
the brake shoes to compensate for lining wear.
direction of drum rotation and an automatic adjustment of
the brake shoes to compensate for lining wear.
Both the wheel cylinder unit and expander unit have cast
integral brake mounting lugs, each taking the brake torque
load. The wheel cylinder unit contains two single acting
hydraulic cylinders with automatic adjusters. The expander
unit contains a double acting hydraulic cylinder with a park
brake wedge expander. Wheel cylinder and expander units
have either a 1-5/8 inch (41,3mm) or 1-3/4 inch (44,5mm)
diameter bore depending upon vehicle brake requirements.
The units are hydraulically connected together with a bridge
pipe or crossover tube.
integral brake mounting lugs, each taking the brake torque
load. The wheel cylinder unit contains two single acting
hydraulic cylinders with automatic adjusters. The expander
unit contains a double acting hydraulic cylinder with a park
brake wedge expander. Wheel cylinder and expander units
have either a 1-5/8 inch (41,3mm) or 1-3/4 inch (44,5mm)
diameter bore depending upon vehicle brake requirements.
The units are hydraulically connected together with a bridge
pipe or crossover tube.
The single web brake shoes are located by slots in the
wheel cylinder tappet head, the expander input tappet/
piston and abutment tappet, and are retained by the shoe
return springs. As with all Bendix automatic adjusting
brakes, provision is made for manual override of the
automatic adjuster. This should only be needed for initial
adjustment of the shoes to a specifi c drum clearance, or to
back off shoes to enable a lipped drum to be removed.
wheel cylinder tappet head, the expander input tappet/
piston and abutment tappet, and are retained by the shoe
return springs. As with all Bendix automatic adjusting
brakes, provision is made for manual override of the
automatic adjuster. This should only be needed for initial
adjustment of the shoes to a specifi c drum clearance, or to
back off shoes to enable a lipped drum to be removed.
The brake assembly incorporates an integral backing
plate (dirtshield) to protect the brake from excessive water
and dirt intrusion. The backing plate (dirtshield) contains
a steady post for each brake shoe to insure that lining
material is kept parallel to the drum braking surface. Both
brake shoes are free to slide on their abutment faces
against the backing plate (dirtshield) and are therefore able
to centralize themselves to the drum. Lining material is 3/4
inch (19,11 mm) thick in the center of the shoe tapering
to approximately 5/8 inch (15,9 mm) at each end. Lining
plate (dirtshield) to protect the brake from excessive water
and dirt intrusion. The backing plate (dirtshield) contains
a steady post for each brake shoe to insure that lining
material is kept parallel to the drum braking surface. Both
brake shoes are free to slide on their abutment faces
against the backing plate (dirtshield) and are therefore able
to centralize themselves to the drum. Lining material is 3/4
inch (19,11 mm) thick in the center of the shoe tapering
to approximately 5/8 inch (15,9 mm) at each end. Lining
CROSS-OVER PIPE
RETAINING SPRING
EXPANDER