Restoring Your Ride: Drum Brake Overhaul

When your vehicle's braking performance starts to feel less than optimal, perhaps with a peculiar noise or a less responsive pedal, it's often a sign that your braking system needs attention. While modern cars predominantly feature disc brakes, many vehicles, particularly on the rear axle, still rely on the robust and cost-effective drum brake system. Understanding how these vital components work and how to maintain them is crucial for your safety on the road. This guide will walk you through the intricacies of drum brakes, from their fundamental operation to a complete replacement and adjustment, ensuring your stops are as reliable as they should be.

Understanding Drum Brakes: The Basics

Drum brakes are a traditional type of braking system that has been used in cars for many years. They operate using friction-lined brake shoes, which are positioned inside a rotating brake drum. As the vehicle moves, the wheels, and thus the brake drums, rotate. When the brake pedal is pressed, small pistons push the brake shoes outwards, pressing their friction material against the inner surface of the brake drum. This contact creates the necessary resistance to slow down or stop the car effectively.

While drum brakes have seen a decline in prevalence compared to their disc brake counterparts in modern front-axle applications, they remain a reliable and effective solution for many vehicles, especially on the rear axle. Their design offers certain advantages, though they also come with distinct characteristics when compared to disc brakes.

Drum Brakes vs. Disc Brakes: A Comparison

Understanding the differences between drum and disc brakes can help you appreciate the role each plays in your vehicle's overall braking performance.

Signs Your Drum Brakes Need Attention

The efficiency of a vehicle's braking system is paramount for on-road safety. Paying close attention to any warning signs can help you identify a problem with your vehicle's drum brakes before it escalates. Addressing these issues promptly is key to maintaining vehicle safety and preventing more extensive repairs.

• Noises From the Vehicle: A vital sign of failing drum brakes is noise emanating from the vehicle's rear end during braking. This can manifest as squealing, grinding, or clunking sounds. Such noises often indicate worn brake shoes, damaged drums, or other internal component issues, leading to reduced braking performance.
• Loose Parking Brakes: If your vehicle's parking brake feels loose, requires excessive pulling, or isn't engaging effectively, it can be a significant indicator of a problem with the drum brakes. Since drum brakes often house the parking brake mechanism, wear or improper adjustment can directly affect its functionality.
• Trouble Stopping the Vehicle: When the drum brakes begin to wear down, you may notice that the stopping distance of your vehicle increases. The car may not halt as quickly or as decisively as it once did, requiring more pedal pressure or a longer distance to come to a complete stop. This reduced stopping power is a critical safety concern.
• Brake Pedal Vibration: If you experience a vibration or pulsation through the brake pedal when applying the brakes, it can indicate issues with the drum brakes. This sensation might be caused by warped or out-of-round brake drums, unevenly worn brake shoes, or other internal irregularities that disrupt smooth contact during braking. This symptom is often associated with a 'faded' or inconsistent pedal feel, where the effectiveness seems to diminish.

The Comprehensive Guide to Replacing Drum Brakes

Replacing drum brakes can seem daunting due to the numerous springs and components, but by following a methodical approach, it's a manageable task for the diligent home mechanic. Remember, safety is paramount throughout this process.

1. Preparation and Safety First

Before you begin, gather all necessary tools and parts. Drum brake replacement, especially on older vehicles, can release hazardous materials like asbestos dust into the air. Always wear a mask and work in a well-ventilated area. Ensure no one else is near the vehicle during the repair.

Prep your vehicle by:

• Removing the wheel covers.
• Loosening the lug nuts while the vehicle is on the ground.
• Using a jack to raise the vehicle and securing it safely with jack stands. Never work under a vehicle supported only by a jack.
• Disengaging the parking brake to allow the drum to be removed freely.

2. Removing the Old Drum and Inspection

With the vehicle safely elevated, remove the wheel and then the brake drum. Some front-wheel-drive cars may have a hub with traditional cone bearings integrated into the drum, requiring the removal of the spindle nut (or axle nut) to take off the entire hub-and-drum assembly. To remove the drum, start by removing any drum retaining screws or clips. The drum should then slide off, though it might be stuck due to rust or tight shoes. You may need to wiggle it, apply a penetrant, or gently tap the face of the drum with a hammer to loosen it. In rare, severe cases, the drum might need to be cut off.

Once the drum is off, you'll see the intricate inner workings of the drum brake assembly: the shoes, springs, and wheel cylinder. Before disassembling, thoroughly spray the entire assembly with brake cleaner to remove dust and grime. Now, carefully inspect the components:

• Brake Shoes: Use a digital micrometer to measure the thickness of the friction material. If it's less than 1/16th of an inch, the brake shoes must be replaced.
• Brake Drums: Inspect for scoring, cracking, grooving, or hot spots. Measure the inside diameter with a brake micrometer and compare it to the specification stamped on the drum. If it has heat cracks, deep gouges, severe hot spots, or exceeds the maximum diameter specification, it must be replaced. If it's within spec and only has minor imperfections, it might be possible to have it machined or 'turned' at a machine shop. However, if you've had to hammer extensively to remove it, it's safer to replace it to avoid vibrations.
• Wheel Cylinders: Check for any leaks of brake fluid. If leaks are present, the wheel cylinders need to be replaced.

3. Disassembly and Component Removal

Before removing any parts, take a clear photo of the brake assembly. This visual reference will be invaluable during reassembly. Use needle-nose pliers or a brake spring tool to pull the shoe-retaining springs. These are typically held by pins that come from the rear and lock into place. Rotate the circular plate/spring until the pin aligns with its slot and pops off. Remove both. Next, carefully remove the horizontal return springs. Specialty spring pliers can make this task much easier.

Once the springs are off, one of the brake shoes and the adjuster mechanism should become loose or even fall out. The other shoe is often attached to the parking brake lever. You'll need to remove a small metal horseshoe clip using a flathead screwdriver or pliers to separate this shoe. Don't worry about damaging this clip, as new ones are typically included in a spring replacement kit.

4. Cleaning and Reassembly

With the old components removed, thoroughly clean the backing plate with a metal brush or sandpaper, and spray generously with brake cleaner. Clean all dirt and rust.

Now, begin reassembling with your new parts:

• Reattach the new shoe to the parking brake lever, securing it with a new horseshoe clip.
• Install the adjuster screw assembly and screw spring.
• Slide the pin through the new shoe from the back, then use your tool to push the plate and spring over the pin, twisting it to lock into place. Do the same for the other shoe, ensuring the adjuster and adjuster lever are correctly positioned between the two shoes as you secure the second holder spring.
• Reinstall the new tensioning springs (horizontal/return springs). It's often easiest to start with the top spring, then the bottom. Again, specialty spring pliers will significantly ease this step.

5. Installing the New Drum and Final Adjustments

Before installing the new drum, clean it thoroughly with a cleaning spray, as some drums come with a thin oil coating for protection. Also, clean the hub face with sandpaper and a metal brush, and sand down any lip on the inside of the drum if you are reusing it. Once prepped, carefully slip the new drum over the brake shoes and onto the hub. If it doesn't slide on easily, the brake shoes might be too tight. Turn the star wheel on the adjuster (usually through the rubber access port on the backing plate) one increment at a time to slightly loosen the shoes until the drum slides on properly without excessive resistance. Ensure the drum is fully seated and fitted correctly.

6. Crucial Post-Installation Steps: Bleeding Brakes and Wheel Installation

This step is absolutely critical and should never be skipped. Bleeding the brakes removes any air that may have entered the brake lines during the process, which can cause a mushy pedal feel and severely reduce braking effectiveness. Always use brand-new brake fluid.

The bleeding process involves attaching a hose to the bleeder valve on each wheel and drawing air out of the system. This can be done by having a second person press the brake pedal, or by using a hand pump or vacuum pump to create suction. Work methodically, typically starting with the wheel furthest from the master cylinder.

Finally, place the wheel back onto the hub and hand-tighten the lug nuts in a star pattern. Once they are snug, remove the jack stands and lower the vehicle to the ground. Use a torque wrench to properly tighten the wheel lugs to your vehicle's specified torque settings. Take your vehicle for a cautious test drive in a safe area to ensure everything feels normal and the brakes are functioning correctly.

When to Replace or Machine Your Brake Drums

The decision to replace or machine (turn) your brake drums depends on their condition. Once the brake drum is off, it's essential to clean and inspect it thoroughly for heat stress cracks, hot spots, or deep gouging. Use a brake micrometer to measure the inside diameter of the drum. This measurement should then be compared to the diameter specification, which is usually stamped visibly on the outside of the drum itself.

• Replace the drum if: It exhibits heat cracks, deep gouges, severe hot spots, or if its measured inside diameter exceeds the manufacturer's specified limit. Extensive hammering during removal can also compromise the drum's integrity, making replacement a safer choice to avoid vibrations.
• Machine (turn) the drum if: It is within the specified diameter limit and only shows minor imperfections that can be corrected by resurfacing. Machining removes a thin layer of material to create a smooth, true surface for the new brake shoes to bed against.

Troubleshooting Stuck Brake Drums

A brake drum can become stubbornly stuck on the axle hub, especially if it's been in place for a long time and rust has set in. Applying penetrating fluid to the hub-drum interface and waiting 10 minutes or longer can help dissolve the rust. A brake drum puller can significantly ease removal, applying even pressure to dislodge it without damaging the axle or drum. Position the puller with its center point pushing on the axle's centre and tighten the jaws to create pressure on the drum. Tapping on the drum or the puller can help break it loose. In the most severe cases, the drum may need to be cut off, but this is a rare last resort.

Frequently Asked Questions About Drum Brakes

Here are some common questions regarding drum brake maintenance and replacement:

Q: Can you put new brake shoes on old drums?
A: Yes, you absolutely can, provided the old drums are in good condition. If they aren't severely rusted, cracked, or beyond their wear limit, you can clean them thoroughly and reuse them. If you notice severe pitting, cracking, or structural damage, they should be replaced.

Q: How many brake shoes are in a drum?
A: Each wheel equipped with a drum brake system typically has two brake shoes inside the drum.

Q: Is the hand brake part of the drum brakes?
A: Yes, it's common for the hand or parking brake mechanism to be integrated into the drum brake assembly, particularly on the rear wheels. The parking brake cable often connects to one of the brake shoes, activating it independently of the hydraulic system.

Q: Do I need to change the brake fluid when replacing drum brakes?
A: While it's not strictly necessary for a shoe replacement unless you open the hydraulic system (e.g., replace the wheel cylinder), it's always good practice to check your brake fluid level and condition. If you replace the wheel cylinder or open the lines, bleeding the system and topping up with fresh fluid is essential.

Q: Is installing new brake pads and shoes safe without changing the brake fluid first?
A: Yes, it is, provided you don't introduce air into the hydraulic system. However, ensure the brake lines aren't too hot to touch and that the master cylinder reservoir doesn't overflow when you push the caliper pistons/wheel cylinders back.

Q: Will my car run okay after I replace the brake pads and shoes?
A: Your car should run perfectly fine, if not better, after a proper drum brake replacement, provided all steps are followed correctly, especially bleeding the brakes. You may notice an initial 'bedding-in' period where braking effectiveness improves slightly.

Q: Are there any special instructions for using my new brake pads and shoes?
A: Not really, beyond standard driving practices. We recommend following your specific vehicle manufacturer's directions for any break-in procedures, which usually involve a series of moderate stops to properly seat the new shoes against the drum.

Q: How often should I change my brakes?
A: The lifespan of your drum brakes depends on your driving habits and vehicle maintenance. A general recommendation is to inspect your brake shoes every 12 months or 12,000 miles, and replace them when they show signs of significant wear, typically when the friction material thickness is below 1/16th of an inch.

Q: What type of brake pads should I use?
A: For drum brakes, you'll be replacing brake shoes, not pads. The best choice depends on your vehicle's specifications. Most modern brake shoes use semi-metallic or organic friction materials. Always use shoes designed for your specific vehicle model and type.

Q: Can I use different brake pads for the front and rear wheels?
A: Yes, it's very common for vehicles to have different types of braking systems and thus different brake components (e.g., disc brakes at the front and drum brakes at the rear), requiring different 'pads' (shoes for drums, pads for discs) for each axle.

Q: Why does my car feel squirrely sometimes when I press down on the brake pedal?
A: This sensation, often described as a 'faded' or unstable pedal, is usually caused by worn brake linings or warped brake drums, which can cause uneven contact or vibration. Replacing your brake shoes and/or drums will typically resolve this issue, restoring a firm and consistent pedal feel.

Q: My car has a manual transmission. Does this mean I can only install drum brakes?
A: Not necessarily. The type of transmission does not dictate the type of brakes. Many vehicles with manual transmissions still use disc brakes, especially on the front axle. If your vehicle originally came with drum brakes, you'd need a significant conversion to switch to discs, which is generally not recommended unless you are an expert.

Q: Where can I buy replacement brake pads and shoes?
A: You can purchase replacement brake shoes and other drum brake components at your local automotive parts store. They are also widely available from various reputable online retailers, often offering a wider selection and competitive pricing.

Conclusion

Maintaining your vehicle's drum brakes is an essential part of ensuring your safety and the longevity of your car. While they may seem complex, understanding their function and following a structured approach to replacement and adjustment can empower you to tackle this crucial maintenance task. From diagnosing tell-tale signs like a vibrating brake pedal to meticulously cleaning and reassembling components, a comprehensive drum brake overhaul will restore your vehicle's stopping power and provide you with peace of mind on every journey. Always prioritise safety, use the correct tools, and don't hesitate to seek professional advice if you encounter challenges beyond your comfort level.

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