SECTION 4E
REAR DRUM BRAKES
DESCRIPTION AND OPERATION
GENERAL DESCRIPTION
This drum brake assembly is a leading/trailing shoe design. Both brake shoes are held against the wheel cylinder pistons by the lower return spring and the fixed anchor plate near the lower return spring. When the brakes are applied, the wheel cylinder pistons move both shoes out to contact the drum. With forward wheel rotation, the forward brake shoe will wrap into the drum and become self-energized. With reverse wheel reta-tion, brake shoes is transferred to the anchor plate through the braking plate to the axle flange. Adjustment is automatic and occurs on any service brake application. Do not switch the position of shoes that have been in service, as this may render the self-adjustment feature inoperative and result in increased pedal travel.
Notice :
- Replace all the components included in the repair kits used to service this drum brake.
- Do not use lubricated shop air on the brake parts, as damage to the rubber components may result.
- If any hydraulic component is removed or disconnected, it may be necessary to bleed all or part of the braking system.
- Replace the shoe and linings in axle sets only.
- The torque values specified are for dry, unlubricated fasteners.
- Perform service operations on a clean bench that is free from all mineral oil materials.
COMPONENT LOCATOR
REAR DRUM BRAKE
- Rear Brake Drum Assembly
- Bleeder Screw
- Bleeder Screw Cap
- Backing Plate
- Wheel Cylinder
- Upper Return Spring
- Adjuster
- Lower Return Spring
- Retain Spring Pin
- Retain Spring
- Retain Spring Plate
- Brake Lining
- Brake Drum Screw
- Brake Drum
DIAGNOSTIC INFORMATION AND PROCEDURES
LINING INSPECTION
- Raise and suitably support the vehicle.
- Remove the rear wheel. Refer to Section 2E, Tires and Wheels.
- Release the parking brake.
- Remove the drum. Refer to "Drum" in this section.
- Inspect the lining for wear or stain with oil
- Measure the lining thickness.
|
Lining Wear Limit Value
|
0.5 mm (0.02 inch)
|
Caution : To avoid injury when servicing brake parts, do not create dust by grinding or sanding the brake linings or by cleaning the wheel brake parts with a dry brush or with compressed air.
Important : Replace the shoe and lining assembly in axle sets only.
- If the measured value is within the limit value, or if the defect is found, replace the lining.
- Install the drum. Refer to "Drum" in this section.
- Install the rear wheels. Refer to Section 2E, Tires and Wheels.
- Lower the vehicle.
REAR DRUMS
Whenever brake drums are removed, they should be thoroughly cleaned and inspected to see if the drums are cracked, scored, deeply grooved, or beyond the specified out-of-round limit.
- A cracked drum is unsafe for further service and must be replaced. Do not attempt to weld a cracked drum. Smooth out any slight scores.
- Heavy or extensive scoring will cause excessive brake lining wear and may require refinishing the drum braking surface.
- If the brake linings are slightly worn but are still reusable and the drum is grooved, polish the drum with a fine emery cloth but do not refinish it. Eliminating all grooves in the drum and smoothing the ridges on the lining removes too much metal and lining. If left alone, the grooves and ridges match, and satisfactory service can be obtained. If the brake linings need to be replace, refinish a grooved drum. A grooved drum, used with a new lining, will not only wear the lining, but also will make it difficult, if not impossible, to obtain proper brake performance.
- An out-of-round drum makes accurate brake shoe adjustment impossible and is likely cause excessive wear of other parts of the brake mechanism. An out-of-round drum can also cause service and irregular tire tread wear, as well as a pulsating brake pedal.
- The extent to which a drum is worn or out-of-round can be measured accurately with an inside micrometer fitted with the proper extension rods. When measuring a drum for wear or the extent to which it is out-of-round, take measurements from the inside edge to the outside edge of the machined surface at 90-degree intervals around the circumference of the drum.
When the drum exceeds the specified out-of-round limit, refinish the drum.
Inspect the brake drum as follow;
- Inspect the drum for crack or damage.
- Measure the inside diameter.
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Inside Diameter Wear Limit Value
|
231 mm (9.1 inch)
|
- If the measured valve is over the limit value, or if the defect is found, replace the drum.
REPAIR INSTRUCTIONS
ON-VEHICLE SERVICE
BRAKE ADJUSTMENT
Removal and Installation Procedure
- Release the parking brake.
- Operate the brake at least 10 times until the jumping of the adjustment spring on the adjustment nut can no longer be heard on either brake drum.
- Raise and suitably support the vehicle.
- Remove the rear wheels. Refer to Section 2E, Tires and Wheels.
- Remove the detent screw from the brake drum.
- Remove the brake drum.
Installation Notice
|
Tightening Torque
|
5 N•m (4 lb-ft)
|
- Using the rear brake adjuster nut, turn the adjuster assembly in until drag is felt on the brake drum.
- Make sure that the parking brake level stops are against the edge of the shoe web. If they are not, loosen the parking brake cable at the equalizer.
Installation Notice
- The brake pedal must be operated more than 10 times. When the clicking can no longer be heard, the clearance between the brake shoe and drum is adjusted.
- Adjust the parking brake. Refer to Section 4G, Parking Brake.
DRUM
Removal and Installation Procedure
- Release the parking brake.
- Raise and suitably support the vehicle.
- Remove the rear wheels. Refer to Section 2E, Tires and Wheels.
- Remove the detent screw from the brake drum.
- Remove the brake drum.
Installation Notice
|
Tightening Torque
|
5 N•m (4 lb-ft)
|
- Inspect the brake drum. Refer to "Drums" in this section.
SHOE AND LINING
Removal and Installation Procedure
- Raise and suitably support the vehicle.
- Remove the brake drum. Refer to "Drum" in this section.
- Remove the retaining spring plate, the retaining spring, and the retaining spring pin.
- Disconnect the upper link of the connecting link spring of the leading shoe. This relieves tension on the upper return spring.
- Remove the upper return spring and the adjuster.
- Remove the leading shoe by unlatching it from the lower return spring.
- Remove the lower return spring.
- Remove the middle spring and the adjuster lever.
- Disconnect the trailing shoe and lining assembly.
Installation Notice
- Measure the minimum brake lining thickness. Refer to "Lining Inspection" in this section.
- Clean the adjuster assembly and apply grease.
- If any parts are of questionable strength or quality because of heat discoloration, excessive stress, or wear, the shoes, the springs, or the adjuster assembly should be replaced.
- Inspect the threads of the adjuster assembly for smooth rotation.
- Do not overstretch the lower return spring and the upper return spring.
- Before installing the brake drum, make sure the adjuster assembly nut is drawn all the way to the stop. The nut must not lock firmly at the end of the adjustment assembly.
- Adjust the parking brake. Refer to Section 4G, Parking Brake.
WHEEL CYLINDER ASSEMBLY
Removal and Installation Procedure
- Raise and suitably support the vehicle.
- Remove the brake drum. Refer to "Drum" in this section.
- Remove the shoe and lining. Refer to "Shoe and Lining" in this section.
- Clean dirt and foreign material from around the wheel cylinder brake line inlet, the pilot, and the bolt.
- Remove the brake fitting nut from the wheel cylinder.
- Plug the opening in the brake line to prevent fluid loss or contamination.
- Remove the wheel cylinder-to-backing plate bolt.
- Gently tap out the wheel cylinder from the backing plate, using care not to damage the bleeder valve or its cap.
Installation Notice
|
Tightening Torque
|
Brake Fitting Nut
|
16 N•m (12 lb-ft)
|
|
Tightening Torque
|
Wheel Cylinder- to-Backing Plate Bolt
|
10 N•m (7 lb-ft)
|
HUB AND BEARING ASSEMBLY
Removal and Installation Procedure
- Raise and suitably support the vehicle.
- Remove the brake drum. Refer to "Drum" in this section.
- Remove the wheel hub cap (dust cap) and the caulking nut from the spindle shaft.
- Remove the hub and bearing assembly.
Installation Notice
|
Tightening Torque
|
235 N•m (173 lb-ft)
|
SPINDLE SHAFT
Removal and Installation Procedure
- Raise and suitably support the vehicle.
- Remove the shoe and lining. Refer to "Shoe and Lining" in this section.
- Remove the hub and bearing assembly. Refer to "Hub and Bearing Assembly" in this section.
- Remove the backing plate-to-spindle shaft nuts.
- Remove the spindle shaft.
Installation Notice
|
Tightening Torque
|
90 N•m (67 lb-ft)
|
BACKING PLATE
Removal and Installation Procedure
- Raise and suitably support the vehicle.
- Remove the shoe and lining. Refer to "Shoe and Lining" in this section.
- Remove the wheel cylinder. Refer to "Wheel Cylinder Assembly" in this section.
- Plug the opening in the brake line to prevent fluid loss or contamination.
- Remove the hub and bearing assembly. Refer to "Hub and Bearing Assembly" in this section.
- Remove the spindle shaft. Refer to "Spindle Shaft" in this section.
- Remove the parking brake retaining clip from the backing plate.
- Separate the backing plate and the gasket.
Installation Notice
UNIT REPAIR
WHEEL CYLINDER
Disassembly and Assembly Procedure
- Remove the wheel cylinder assembly from the backing plate. Refer to "Wheel Cylinder Assembly" in this section.
- Twist off the boots, the pistons, and the seals from each end of the wheel cylinder.
- Remove the spring assembly.
- Remove the bleeder cap and the bleeder valve.
Installation Notice
|
Tightening Torque
|
6 N•m (4 lb-ft)
|
- Inspect the wheel cylinder bore and the pistons for scoring, nicks, corrosion, and wear.
- Use a crocus cloth to polish out light corrosion in the wheel cylinder bore.
- If the bore will not clean up with a crocus cloth, replace the wheel assembly.
- Clean all the parts in clean denatured alcohol or brake fluid. Dry all the parts with unlubricated compressed air and lubricate the new seals, the pistons, and the wheel cylinder bore with clean brake fluid before assembly.
- Thinly coat all the parts except the dust caps with brake fluid.
- Inspect the pistons for free movement.
- After the installation, bleed the brake system. Refer to Section 4A, Hydraulic Brakes.
SPECIFICATIONS
GENERAL SPECIFICATIONS
|
Application
|
Unit
|
Description
|
|
Drum
|
Inside Diameter
|
mm (inch)
|
230 (9.06)
|
|
Wear Limit
|
mm (inch)
|
231 (9.09)
|
|
Out of Round
|
mm (inch)
|
0.1 (0.0039)
|
|
Brake Lining
|
Thickness
|
mm (inch)
|
MIN. 4.7 (0.185)
|
|
Wear Limit
|
mm (inch)
|
0.5 (0.02)
|
|
Distance Between Lining and Drum
|
mm (inch)
|
0.2~0.45 (0.0079~0.0177)
|
|
Wheel Cylinder
|
Diameter of the Piston
|
mm (inch)
|
20.64 (0.8126)
|
FASTENER TIGHTENING SPECIFICATIONS
|
Application
|
N•m
|
Lb-Ft
|
Lb-In
|
|
Brake Drum Detent Screw
|
5
|
4
|
44
|
|
Brake Fitting Nut (Wheel Cylinder)
|
16
|
12
|
-
|
|
Wheel Cylinder-to-Backing Plate Bolt
|
10
|
7
|
89
|
|
Caulking Nut
|
235
|
173
|
-
|
|
Backing Plate-to-Spindle Shaft Nut
|
90
|
67
|
-
|
|
Bleeder Valve Screw
|
6
|
4
|
53
|
