Drum Brake Replacement Techniques

Study Notes

Drum Brake Replacement Techniques

Drum brakes are a crucial component for automotive braking systems, known for durability and reliability
Understanding the process of replacing drum brakes is vital for maintaining vehicle safety and performance
Drum brakes have several key components that work together, including brake shoes and springs, wheel cylinders, and adjusters, converting mechanical energy to thermal energy to slow or stop the vehicle
Replacing drum brakes involves a systematic approach of disassembly, inspection, adjustment, and reassembly to ensure optimal performance and safety

Drum Brake Components

Backing Plate: A thin, metal-based band placed behind the drum brake; serves as a protective shield for other components; circular shape with holes and protrusions to match the standard drum brake part
Wheel Cylinders: Components that convert fluid pressure into mechanical motion; vital for the braking mechanism; dual piston wheel cylinders are common due to accompanying leading and trailing drum types; these cylinders include housing, bleeder nut, piston boot, spring and piston
Brake Shoes and Pads: Often found in drum brakes; a brake shoe or pad facilitates braking; brake shoes have a circle shape consisting of two semicircle shoes, and brake pads are placed on the brake shoes; brake pads are made of organic ceramic
Return Spring: An important component in drum brake systems; responsible for returning the brake shoe to its original position upon release of pressure from brake lever or pedal; it includes an upper spring and a lower spring, with the latter maintaining the position of the brake shoes on the adjuster
Brake Shoe Holder: Attaches the brake shoes to the backing plate in the drum brake system; consists of various parts, including pins, springs, and a pressure plate, for added support and stability to the drum brakes
Brake Shoe Adjuster: Located at the bottom of the drum brake; its shape resembles a screw on an adjuster; adjusting the gap between the drum brake pads and the drum surface to ensure smooth braking operation
Parking Brake Lever: A lever exclusively found in cars and designed for parking brake functionality; its construction includes two levers - park brake lever and brake shoe link; one end of the lever has a hinge attached to the brake shoe, while the other is attached to the brake cable
Drum Brake: A component in the drum brake system, a medium for friction with brake pads to slow or stop vehicle wheels; made of cast steel with a drum or tube shape; directly connected to wheel bolts

Steps to Replace Drum Brakes

Step 1: Wear an asbestos respirator to protect against hazardous brake dust
Step 2: Remove the hubcap and loosen the lug nuts; block the front wheels with wheel chocks; jack up the car and secure it on jack stands; do not work on a car supported by a jack alone (use stands to guarantee safety).
Step 3: Spray the hub of the wheel with penetrating oil (like PB Blaster)
Step 4: Grip the brake drum edges and pull it off while wiggling it to aid removal; back off the brake adjuster to facilitate removal of the drum
Step 5: If brake drums are held on by screws, remove them first as per needed
Step 6: Examine the drum for any damage—scoring requires refacing or replacement. Take detailed pictures or drawings of the component setup before disassembling so you can put it back together correctly
Step 7: Place the whole brake mechanism in a container and spray it with brake cleaner to keep the dust from becoming airborne (asbestos dust is hazardous)
Step 8: Compare the new brake shoes with the old ones; ensure they are the same shape, holes, and width
Step 9: Dismantle the brake by removing the shoe return springs, detaching the parking brake lever, and removing retaining pins and springs; spread the shoes apart from the top and disengage the shoes from the wheel cylinder pins
Step 10: Carefully reassemble the brake components using cleaning materials and reattaching necessary parts like the return springs and parking brake lever
Step 11: Check the reassembled brake components against the previously taken images or detailed drawings to ensure precise assembly and accurate placement
Step 12: Reinstall the tire and torque the lug nuts along with reinstalling and attaching the hubcap; repeat the process on the other side; bleed the brake system and road test the vehicle to make sure everything is working properly