Do Drum Brakes Automatically Adjust?

Yes—most drum brakes built from the mid-1960s onward include a self-adjusting mechanism that automatically compensates for lining wear, usually when you brake while reversing or when you use the parking brake. However, not all systems are self-adjusting, and even those that are can stop working if parts are worn, corroded, misassembled, or neglected, which may require manual adjustment or repair. Understanding which system you have and how it works can help you maintain consistent braking performance and pedal feel.

How Automatic Adjustment Works

Self-adjusting drum brakes maintain a small, consistent clearance between the brake shoes and the drum. As shoes wear, an adjuster expands incrementally, keeping the pedal travel and braking response stable. The mechanism typically relies on a star-wheel adjuster screw and a lever that advances it when certain conditions are met.

Two Common Self-Adjuster Activation Methods

Most vehicles use one of two activation methods. The following list outlines how each approach triggers the adjuster.

• Reverse-braking actuation: When you back up and apply the brakes firmly, the primary (leading) shoe shifts enough to move a lever that clicks the star wheel forward, lengthening the adjuster screw.
• Parking-brake actuation: Applying the parking brake pulls a cable or link that moves the adjuster lever, advancing the star wheel to take up slack in the system.

Both designs only advance when shoe-to-drum clearance exceeds a threshold, so you may not notice an adjustment every time. Proper assembly and free movement of parts are essential to reliable operation.

When They Do Not Adjust Automatically

Even self-adjusting systems can fail to take up wear if key components are compromised. The next list covers common reasons self-adjustment stalls.

• Corroded or seized star wheel/adjuster screw threads that won’t turn.
• Weak, stretched, or broken return and adjuster springs.
• Misassembled hardware (e.g., shoes swapped left/right, lever on the wrong side, missing anti-rattle components).
• Damaged, frayed, or disconnected parking-brake cables on parking-brake–actuated systems.
• Contamination or glazing that prevents the shoe from moving far enough to trigger the lever.
• Older vehicles or aftermarket conversions that use manual-only adjusters.

If any of these conditions exist, the brakes may require manual adjustment and hardware service before the self-adjusters will resume working.

Signs Your Drum Brakes Are Out of Adjustment

Out-of-adjustment drums often give noticeable symptoms. The following points can help you recognize the condition early.

• Longer brake pedal travel or a low, “spongy” pedal with normal hydraulic feel otherwise.
• Poor parking-brake holding power or a high parking-brake lever/foot-pedal position.
• Rear-wheel braking that feels weak, especially under light-to-moderate braking.
• Uneven braking or pulling if one side adjusts and the other does not.
• Audible scraping or squeal from excessive shoe-to-drum clearance or contamination.

These symptoms can overlap with other brake issues, so confirm with inspection rather than relying on feel alone.

How to Encourage Self-Adjustment Safely

If your system is designed to self-adjust and is in good order, you can prompt it to take up slack. The steps below describe typical procedures—always follow your vehicle’s service manual.

• For reverse-actuated systems: In a safe, open area, back up slowly and apply the brakes firmly to a near stop. Repeat 3–5 times. You may notice improved pedal height afterward.
• For parking-brake–actuated systems: With the vehicle stationary, apply and release the parking brake fully 5–10 times. Avoid driving with the parking brake engaged.
• Verify drag: After adjustment, a properly adjusted drum may exhibit a very light, even drag when the wheel is spun off the ground by hand.
• Access-hole check: Some backing plates have a rubber plug; removing it allows a technician to confirm star-wheel position or make minor manual corrections.

If these steps don’t improve pedal feel or holding power, the adjuster mechanism may be stuck or misassembled and should be serviced.

Maintenance and Service Tips

Regular service keeps self-adjusters working and extends brake life. The following practices are standard in professional shops.

• Clean and lubricate the adjuster screw threads with a high-temperature brake lubricant during brake jobs.
• Replace the hardware kit (springs, clips, adjuster lever, and cable/link) whenever you replace shoes.
• Inspect backing plate shoe contact pads; dress minor grooves and apply a thin film of appropriate brake grease.
• Confirm correct shoe orientation: primary (shorter lining) shoe toward the front, secondary (longer lining) toward the rear, unless your service manual specifies otherwise.
• Check parking-brake cables for smooth operation and free return; replace seized or frayed cables.
• Ensure drums are within spec and not overly worn or out-of-round; machine or replace as needed.

These routine steps help ensure the adjuster can move freely and the mechanism can operate as designed between service intervals.

Related: Disc Brakes and “Drum-in-Hat” Parking Brakes

Disc brake calipers are inherently self-adjusting: the caliper piston maintains pad-to-rotor clearance as pads wear. However, vehicles with rear disc brakes often use a small “drum-in-hat” parking brake inside the rear rotor hat. Those miniature drum shoes typically rely on a manual star-wheel adjustment during service, and some electronic parking-brake systems perform software calibrations rather than mechanical self-adjustment.

Summary

Most modern drum brakes do automatically adjust through a built-in self-adjuster mechanism activated by reverse braking or the parking brake. But proper operation depends on clean, lubricated components, correct assembly, and intact hardware. If your pedal feels low, the parking brake is weak, or repeated reverse stops don’t help, the self-adjuster may be stuck or the system may require manual adjustment and service.

Do drum brakes adjust on their own?

Yes, most drum brakes are designed with self-adjusting mechanisms that automatically compensate for wear on the brake shoes, but they often require manual intervention to function correctly or at all. These self-adjusters typically work by shifting a component when the brakes are applied in reverse, causing a star wheel to advance, which tightens the brake shoes closer to the drum as they wear down. However, issues like rust or dirt, improper installation, or the absence of the correct parking brake usage can prevent the self-adjuster from working properly, leading to decreased braking performance.
 
This video explains how the self-adjusting mechanism works: 57sThomas EXOVCDSYouTube · Sep 22, 2019
How self-adjusters work

• The role of wear: As the brake shoes wear down, they move further from the drum. 
• The actuating mechanism: When the brakes are applied in reverse, the self-adjusting mechanism activates. A component, sometimes called a “pole,” moves to contact the star adjuster. 
• The adjustment process: This contact causes the star wheel to rotate, tightening the brake shoes to take up the increased distance created by the shoe wear. 
• The need for reverse: This action is often triggered when driving in reverse, as it allows the assembly to shift and the adjuster to advance. 
• Parking brake usage: For some vehicles, using the parking brake can also engage the self-adjusting mechanism. 

Why they might not work

• Rust and dirt: Corrosion or dirt can prevent the self-adjuster assembly from moving or functioning correctly. 
• Improper adjustment: If the drum brakes were not initially set up correctly, the self-adjuster may not function as intended. 
• Incorrect use of the parking brake: In some cases, consistent use of the parking brake is necessary for the self-adjuster to operate properly. 
• Worn or broken parts: The self-adjuster assembly itself can become worn or damaged, preventing it from doing its job. 

What to do if they aren’t adjusting

• Check for manual adjustment: If the drum brakes aren’t self-adjusting as they should, they may need a manual adjustment to function correctly. 
• Consult a professional: A mechanic can properly diagnose why the self-adjusting mechanism is failing and perform the necessary adjustments or repairs. 

How self-adjustment works on a brake drum?

As the brake linings wear, the shoes must travel a greater distance to reach the drum. In systems fitted with automatic adjusters, when the distance reaches a certain point, a self-adjusting mechanism automatically reacts by adjusting the rest position of the shoes so that they are closer to the drum.

How to tell if brakes are self-adjusting?

Visual Identification
To check if brakes are self-adjusting without removing the hub, remove the adjuster slot plugs on the backside of the brakes (Fig. 1A) and shine a flashlight in the holes. If the brakes are self-adjusting, the silver lever (Fig. 2A) that rotates the star lever will be visible.

Do parking brakes adjust themselves?

Yes, many modern parking brakes are designed to be self-adjusting, but this often depends on the specific vehicle and brake type. Self-adjusting mechanisms are typically integrated into drum brakes to maintain proper clearance between the brake shoes and the drum, or a system can adjust the cable length from the pedal for consistent travel. However, these systems can become frozen with age or disuse, requiring manual adjustment or replacement of components to restore proper function. 
How Self-Adjusting Parking Brakes Work 

• Drum-In-Hat Systems: Opens in new tabIn some drum brake setups, the parking brake mechanism includes a self-adjuster that is actuated by applying the parking brake. This mechanism tightens the brake shoes to take up slack as they wear, which helps maintain consistent pedal feel and holding power.
• Cable-Based Self-Adjusters: Opens in new tabSome vehicles have a self-adjusting feature that works on the parking brake cable. Instead of the wheels, the adjustment occurs at the pedal or an equalizer bar, managing the cable’s length to ensure consistent pedal travel over time, even as the brake shoes wear.

Why They Might Not Work

• Lack of Use: The most common reason for a self-adjusting parking brake to fail is that it isn’t used regularly. This leads to the adjuster components becoming stuck and unable to function. 
• Wear and Tear: Cables can become worn, rusted, or corroded, losing their tension and function, according to Firestone Complete Auto Care. 
• Initial Adjustment Needed: For some self-adjusting systems, the brakes may still require an initial manual adjustment before the self-adjuster can begin its work properly. 

When to Seek Professional Help

• If you notice increased travel in your parking brake pedal or if the parking brake doesn’t hold the vehicle securely, it may be time for a professional to check and adjust it. 
• A qualified mechanic can identify if the adjuster is frozen or if the components are too worn and need replacement.