10/01/2015
Reinstalling a brake drum correctly is the final, crucial step in completing a rear brake shoe replacement. While the process of replacing brake shoes can be intricate, varying slightly between manufacturers due to diverse system designs, getting the drum back on properly is paramount for your vehicle's safety and braking efficiency. This detailed guide will walk you through the entire process, providing technical insights and practical tips to ensure you perform the job with confidence and precision, making sure your vehicle is roadworthy and reliable.
Safety First: Essential Preparations
Before you even think about putting tools to metal, safety must be your absolute priority. Working on your vehicle's braking system requires a meticulous approach to prevent injury and ensure the repair is sound. Always don the appropriate personal protective equipment, including safety glasses and gloves, especially when dealing with brake dust, which can contain harmful particles. The dust created by worn brakes should be treated with caution; avoid inhaling it. Using a bucket with water to rinse away dust particles, as described later, is an excellent practice to minimise airborne contaminants.
To begin, park your car on a level, firm surface. Engage the front wheels with sturdy wheel chocks to prevent any movement. Crucially, ensure the parking brake is completely disengaged, as it will impede the removal and reinstallation of the drum. A vital tip for any DIY mechanic is to work on only one side of the vehicle at a time. This allows the untouched side to serve as a valuable reference point for how the components should be assembled. A quick picture taken with your phone before disassembly can also be an invaluable aid. Once prepared, use a robust floor jack to raise the rear of the car and securely support it with jack stands. Never rely solely on a jack for support. Finally, remove the rear wheel from the car to gain full access to the braking components.
The Foundation: Installing New Brake Shoes
Before you can even consider reinstalling the brake drum, the new brake shoes must be correctly fitted. This is a complex but essential part of the process, as the drum's fit and subsequent braking performance depend entirely on the shoes being perfectly positioned and adjusted.
Checking the Wheel Cylinder
With the old brake shoes removed, you'll have a clear view of the wheel cylinder. This component is critical for hydraulic brake operation. Use a small, flat-blade screwdriver to gently pull back the rubber dust boots on either end of the wheel cylinder. Look for any signs of brake fluid leakage. Even a small amount of fluid indicates a failing seal, necessitating replacement. While it's often recommended to replace wheel cylinders every time new brake shoes are installed, especially if the vehicle is older or has high mileage, you might get away with leaving them if they are relatively new and show no signs of leakage. However, if one side is leaking, it's highly advisable to replace both wheel cylinders as a pair, as the other side is likely not far behind.
Transferring Components to New Shoes
The new brake shoes typically come without the springs, parking brake lever, or self-adjuster mechanism attached. These components must be transferred from the old shoes to the new ones. Lay the old and new brake shoe sets side-by-side on a clean, flat workbench. This side-by-side comparison is crucial for understanding the correct orientation and placement of each spring and lever. Take another photo with your phone if it helps clarify the arrangement.
Begin by carefully removing the springs and the parking brake lever from the old shoes and installing them onto the corresponding positions on the new shoes. This is also an opportune moment to consider installing a new brake spring hardware kit. Springs can become brittle and lose their strength over time, particularly if they've been subjected to excessive heat cycles. If your vehicle's brakes have overheated, or if it has covered more than 80,000 miles, replacing the entire hardware kit (springs, retainers, etc.) is a wise investment in long-term reliability.
Next, remove the self-adjuster mechanism from the old shoe set. If it's the threaded type, disassemble it and thoroughly clean the threads. Apply a small amount of high-temperature brake lubricant to the threads to ensure smooth operation and prevent seizing. Reset the adjuster by pushing the adjuster wheel away from the pin or twisting the threads inwards to make it as short as possible. This ensures that when the drum is reinstalled, there's enough clearance for it to slide over the new, thicker shoes. It's paramount to avoid getting any dirt, grease, or brake fluid on the new brake shoe linings, as this will severely inhibit their braking performance. If contamination occurs, use a small amount of dedicated brake cleaner and a clean shop towel to carefully remove it.
Mounting the New Shoe Assembly
With the new shoes fully assembled with their springs and levers, they are ready for installation onto the backing plate. This step often feels like it requires an extra set of hands! Use needle-nose vice grips to hold the parking brake cable spring downward, keeping it away from the cable end. This allows you to easily attach the parking brake lever to the cable.
Carefully reposition the entire shoe set onto the backing plate, ensuring they sit correctly over the wheel cylinder. While holding the shoes in place, install the brake shoe retainer clips. There's typically one on each shoe, and a specific brake shoe removal tool can make this task much easier. Once the retainer clips are secure, reposition and attach the lower brake spring using your needle-nose vice grips. To complete the assembly, connect one side of the upper spring to a brake shoe. Then, using your needle-nose vice grips, grasp the spring and pull it towards the secondary shoe to connect the other end. This completes the physical assembly of the brake shoes.
Pre-Adjusting the Self-Adjuster
All drum brake systems incorporate some form of self-adjuster mechanism. Before reinstalling the drum, it's essential to reset this adjuster to its shortest position. This provides the necessary clearance to slide the drum back over the newly installed shoes. Initial adjustment is crucial to prevent the drum from becoming stuck or the shoes from being too tight, which can lead to overheating and premature wear. The fine-tuning will happen once the drum is on.
The Main Event: Reinstalling the Brake Drum
This is the moment you've been working towards – putting the drum back in place. Proper reinstallation is not just about sliding it on; it involves precise adjustment to ensure optimal braking performance.
Drum Inspection and Preparation
Before reinstallation, thoroughly inspect your brake drum. If you're replacing the drum, ensure the new one is an identical match to the old one. If you're reusing the old drum, it's imperative that it's either in excellent condition or has been re-machined by a professional. Brake drums have a specified maximum diameter, which indicates the limit to which they can be re-machined. Removing too much material reduces the drum's ability to dissipate heat, leading to brake fade and potential warping, which causes uneven braking and can be highly dangerous. Look for any signs of uneven wear, such as a prominent lip on the outer edge, which will prevent the new, perfectly flat brake shoes from making full contact, severely affecting braking ability.
Before fitting, use a clean shop towel and a dedicated brake cleaner (or carburetor cleaner) to meticulously wipe out the drum's inner shoe contact surface. This removes any contaminants, ensuring maximum friction between the shoes and the drum.
The Reinstallation Process: Step-by-Step
- Carefully slide the re-machined or new brake drum back onto the axle. As you do this, gently spin the drum.
- Now comes the critical adjustment phase: With the drum on, use a flathead screwdriver or brake spoon (depending on your drum's design) to subtly move the shoe self-adjuster outwards, one click at a time. After each adjustment, spin the drum. You're aiming for a very slight, consistent contact between the brake shoes and the drum. The drum should spin freely but with a gentle, audible drag from the shoes. This process may require several attempts to achieve the perfect fine-tuning. If the drum doesn't spin freely, or feels too tight, you've over-adjusted the shoes, and the drum must be removed to retract the self-adjuster slightly.
- Once satisfied with the shoe-to-drum clearance, if your vehicle's drum is secured by an axle bearing retainer nut, carefully insert it by hand. This prevents accidental cross-threading, which can damage the axle threads. Some drums simply slide onto the axle without a retaining nut.
- After hand-threading, use a torque wrench to tighten the retainer nut to the manufacturer's specifications. These specifications typically range between 170 and 240 foot-pounds of torque. Even after tightening the nut, the brake drum should continue to spin freely with minimal contact from the brake shoes.
WARNING: Do not make the critical mistake of thinking the shoes will simply "wear in" if they are too tight. This is a dangerous misconception. If the shoes are set too tightly, the friction will generate excessive heat, causing the brake components to expand. This expansion will worsen the problem, potentially leading to the wheel locking up completely, which is extremely hazardous, especially at speed.
- Finally, reinsert the bearing dust cap. Gently tap it into place using a hammer. These caps are often made of thin sheet metal, so be careful not to deform or bend them by hammering too hard. A distorted cap will lose its ability to securely hold onto the drum and will need to be replaced.
Once both sides of the vehicle's rear brakes have been completed, follow the appropriate guide for reinstalling the wheels and safely lowering the car from the jack stands.
Post-Installation Checks and Adjustments
The job isn't quite finished when the wheels are back on. Several vital checks and adjustments are necessary to ensure the braking system is fully functional and safe.
Brake Fluid Level Verification
Lift the bonnet and locate the brake master cylinder fluid reservoir. Before opening it, clean the top to prevent contaminants from entering the system. Loosen and remove the cap. Check the fluid level against the 'MAX' or 'FULL' line. If it's low, carefully add fresh brake fluid from a sealed container until the level reaches the designated mark. Never overfill. Reinstall and tighten the reservoir cap securely.
Setting the Rear Brake Shoes
Once the car is back on the ground and both rear wheels are reinstalled, the brake shoes need a final adjustment, or 'setting', to the drum. This is typically achieved by repeatedly applying the brake pedal and then actuating the parking brake lever. Depress the brake pedal several times, then engage and release the parking brake lever multiple times. This action helps the brake shoe self-adjuster mechanism to automatically fine-tune the shoe-to-drum clearance, ensuring proper engagement and increasing the firmness of the brake pedal.
Bleeding the Brake System (If Necessary)
While not always required for a simple brake shoe replacement, if you opened the hydraulic system (e.g., replaced a wheel cylinder), or suspect air has entered the lines, you must bleed the brake system. Air in the brake lines will result in a spongy brake pedal and reduced braking effectiveness, making the vehicle unsafe to drive. Consult your vehicle's service manual for the correct bleeding procedure.
Test Drive and Final Inspection
After all checks and adjustments, take your vehicle for a cautious test drive in a safe, quiet area. Pay close attention to the feel of the brake pedal – it should be firm and consistent. Listen carefully for any abnormal noises, such as squealing, grinding, or clunking sounds, which could indicate a problem with the installation or a faulty component. Test the parking brake engagement. If anything feels or sounds amiss, stop immediately and re-inspect your work. A thorough check now can prevent serious issues later.
Important Considerations and FAQs
Understanding these additional points can help you maintain your drum brakes effectively and troubleshoot common issues.
Are drum brakes susceptible to moisture?
Yes, drum-style brakes are inherently more susceptible to moisture, such as water ingress, compared to disc brakes. Water inside the drum can significantly decrease braking ability, especially immediately after driving through deep puddles or heavy rain, as it reduces the friction between the shoes and the drum.
When should I replace spring hardware?
Always inspect the spring hardware (return and mounting springs) during brake shoe replacement. If any springs appear damaged, stretched, or broken, they must be replaced. For larger vehicles or those with high mileage, it's often a good practice to replace the entire spring hardware kit every time the brake shoes are replaced, as springs can lose their tension and become brittle over time due to heat cycling.
Do all drum brake systems self-adjust?
While most modern drum brake systems feature an automatic self-adjuster, some older systems or specific applications may require manual adjustment after assembly. These systems typically provide an adjustment slot on the backing plate or drum, allowing you to manually turn an adjuster wheel with a brake spoon or screwdriver to achieve the proper shoe-to-drum clearance.
Why is quality important for brake components?
Always use high-quality, reputable brand brake shoes and hardware. Inferior parts can lead to premature wear, reduced braking performance, and even component failure, compromising your safety on the road. The longevity and effectiveness of your repair are directly tied to the quality of the parts you install.
What if I hear abnormal noises after the job?
Any abnormal noises, such as squealing, grinding, or clunking, after a brake job indicate a problem. This could be anything from improperly installed components, a faulty part, or a drum that needs re-machining or replacement. Do not ignore these sounds; stop driving and re-inspect your work thoroughly. If you cannot identify the issue, it's best to consult a qualified mechanic.
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