Parts of Rear Drum Brakes

Rear drum brakes typically consist of the brake drum, two brake shoes (primary and secondary) with friction linings, a wheel cylinder, a backing plate, return and hold‑down springs, a self‑adjuster mechanism (star wheel, screw, and lever or cable), an anchor pin, and parking‑brake components (lever and strut). Depending on the vehicle, the assembly may also integrate the hub/bearing and include ABS hardware such as a tone ring and wheel‑speed sensor. Below is a clearer look at each piece and how it contributes to stopping power and parking‑brake holding force.

Core components and their functions

These are the main structural and hydraulic parts that convert pedal pressure into friction at the rear wheels.

• Brake drum: The cast‑iron ring that rotates with the wheel; the shoes press outward against its inner surface to create friction and slow the vehicle.
• Brake shoes (primary and secondary): Curved steel shoes lined with friction material; the primary (usually with shorter lining) faces the front of the vehicle, and the secondary (longer lining) faces the rear to provide greater braking force in many designs.
• Friction linings: Bonded or riveted material on the shoes that actually contacts the drum; formulated for heat resistance and wear.
• Wheel cylinder: Hydraulic cylinder with two pistons that push the shoes outward when brake fluid pressure rises; includes dust boots and a bleeder screw.
• Backing plate: Stamped steel plate bolted to the axle or knuckle; supports shoes and hardware and serves as a reaction surface.
• Anchor pin: Fixed post at the top (or top and bottom) of the backing plate where shoes and springs register, controlling shoe movement.
• Hub/bearing (if integrated): Some drums are built into the hub and contain the wheel bearing and wheel studs; others use a separate drum that slides over the studs.

Together, these components translate hydraulic force into controlled friction, with the backing plate and anchor pin governing shoe geometry and the wheel cylinder delivering the clamping action.

Hardware, springs, and the self‑adjuster

Springs and adjuster parts control shoe return, retention, and the automatic compensation for lining wear.

• Return springs (primary and secondary): Heavy springs that pull the shoes back from the drum when you release the pedal.
• Hold‑down springs, pins, and cups: Retain each shoe against the backing plate while allowing limited sliding motion.
• Self‑adjuster assembly: Typically includes a star wheel and threaded adjuster screw between the shoes, plus a lever/pawl and either a cable or link; advances the star wheel to keep the shoe‑to‑drum clearance correct as linings wear.
• Guide plates/anti‑rattle clips: Small clips or plates that stabilize shoes and reduce noise.
• Lubrication pads: Raised pads on the backing plate where shoes slide; require a thin film of high‑temp brake grease.
• Inspection plug and adjuster slot: Rubber plug and access window on the backing plate for checking or manually turning the star wheel.

This hardware ensures the shoes move smoothly and consistently, and that the brake pedal remains firm by automatically maintaining the correct shoe clearance.

Parking‑brake components

The parking‑brake (handbrake) uses mechanical linkage inside the drum to hold the vehicle stationary without hydraulic pressure.

• Parking‑brake lever (actuating lever): Attached to the trailing shoe; converts cable pull into shoe expansion.
• Parking‑brake strut/bar: Rigid bar between shoes that transmits parking‑brake force and balances load.
• Parking‑brake cable and equalizer: Cable from the cabin lever or pedal to the rear brakes; the equalizer divides force left and right.
• Lever return spring: Dedicated spring that returns the parking‑brake lever to rest when released.

These parts deliver reliable mechanical holding force independent of the hydraulic system, critical for parking and as a backup in emergencies.

ABS and sealing‑related parts around the drum

Many modern vehicles integrate wheel‑speed sensing and protective elements near or within the drum/hub area.

• ABS tone ring (reluctor): Tooth ring used by the ABS to measure wheel speed; may be pressed on the axle, integrated into the hub, or located behind the drum.
• Wheel‑speed sensor and grommet: Sensor reads the tone ring; wiring passes through seals to prevent contamination.
• Dust shield/splash guard: Metal shield that helps keep water and debris off the assembly.
• Grease/dust cap (serviceable bearings): On some older RWD designs, caps protect user‑serviceable bearings within an integrated hub/drum.
• Axle/hub seals: Seals that prevent gear oil or grease from contaminating the brake shoes and drum.

While not all vehicles share the same layout, these elements protect the brake from contamination and enable ABS to function accurately.

Common design variations

Drum brakes come in several configurations that change how parts look or interact but keep the same core purpose.

• Duo‑servo vs. leading‑trailing: Duo‑servo designs link shoes via an adjuster and floating anchor to amplify braking in reverse/forward; leading‑trailing uses a fixed anchor and distinct shoe roles for consistent response.
• Integrated vs. slip‑on drums: Some drums are integral with the hub and bearing; others slip over wheel studs for easier service.
• Automatic vs. manual adjusters: Most modern systems auto‑adjust during reverse braking; older or simpler setups may rely on periodic manual adjustment.
• Shoe identification: In most setups, the primary shoe has a shorter lining and faces the front; the secondary has a longer lining and faces the rear.

Knowing which design you have helps with correct assembly, adjustment, and diagnosis after service.

Maintenance and service considerations

Proper care extends the life of drum components and preserves braking performance.

• Inspection intervals: Check rear drums, shoes, cylinders, and hardware at regular service or every 20,000–30,000 miles, or sooner if symptoms appear.
• Replace hardware as a kit: Springs and small parts fatigue with heat cycles; replacing them with the shoes is best practice.
• Measure the drum: Verify inside diameter against the maximum spec cast into the drum; resurface only if within spec.
• Check for leaks: Inspect wheel‑cylinder boots and axle seals; any fluid on the shoes requires shoe replacement and leak repair.
• Clean safely: Use brake cleaner and avoid blowing dust; wear appropriate respiratory protection.
• Lubricate contact points: Apply a thin film of high‑temp brake grease to backing‑plate pads—never on friction surfaces.
• Adjust and bed‑in: Set shoe clearance correctly and bed the brakes per the lining manufacturer’s guidance.

Following these steps improves pedal feel, braking balance, and the longevity of both friction and hardware components.

Common symptoms of wear or failure

These signs often point to specific drum‑brake issues that warrant inspection and repair.

• Long pedal travel or soft pedal: Out‑of‑adjustment shoes or a leaking wheel cylinder.
• Poor parking‑brake hold: Glazed/contaminated linings, misadjusted cables, or worn strut/lever components.
• Pulling, grabbing, or chatter: Uneven shoe wear, weak/broken return springs, or distorted drum.
• Squeal, grind, or scraping: Worn linings to the rivets/bond line or scored drum surface.
• Burning smell or hot drum: Sticking wheel cylinder, seized parking‑brake lever, or over‑tight adjuster.
• Fluid or grease on backing plate: Wheel‑cylinder brake fluid leak or axle seal failure contaminating the shoes.

Addressing these symptoms promptly restores braking safety and prevents more costly damage to drums and shoes.

Summary

Rear drum brakes are built from a brake drum, two shoes with linings, a wheel cylinder, a backing plate, anchoring hardware, return and hold‑down springs, and a self‑adjuster, with additional parking‑brake levers and struts and, on many vehicles, ABS‑related parts. Understanding what each part does—and how designs vary—makes it easier to service the brakes correctly, diagnose issues quickly, and keep stopping distances short and consistent.

What are the parts of the rear brake?

Main parts of rear drum brakes: 1-Baking plate, 2-Drum, 3-Brake shoe, 4-Shoe lining, 5-Rivet, 6Brake adjuster, 7-Elements for holding the shoes, 8-Shorter return spring, 9-Longer return spring, 10-Lever mechanism of the parking brake 11-The return spring.

What does a drum brake consist of?

And now we can remove the wheel hub. Assembly. Now there’s a few main components that go into this drum brake assembly. We have the wheel cylinder up here which is your hydraulic piston.

What are the 5 parts of a drum brake system?

Drum Brake Components

• Backing Plate. The backing plate is one of the drum brake components in the form of a metal-based band which is relatively thin and is placed on the back of the drum brake system.
• Wheel Cylinders.
• Brake Shoes and Pads.
• Return Spring.
• Brake Shoe Holder.
• Brake Shoe Adjuster.
• Parking Brake Lever.
• Drum Brake.

What parts to replace on drum brakes?

If the thickness of the brake shoes is less than 1/16th of an inch, the brake shoes should be replaced. Next, go for the brake drums for any scoring, cracking, or grooving. Also, inspect the wheel cylinders for any leaks of brake fluid. If so, then the wheel cylinders need to be replaced.