Buzz
Within a vehicle's braking mechanism, the brake pads are securely positioned.
iStockphoto.com/Brian SullivanWhoa -- there's a reason we're advised to check both sides before crossing the road. That pedestrian shouldn't have stepped onto the street. Clearly, she didn't notice you. So you slam on the brakes, and she leaps back. Crisis averted -- except that loud screeching noise isn't coming from her. It's emanating from your vehicle.
It seems like your brakes might need relining. Don't fret; brake relining is among the most routine forms of brake upkeep. It's a straightforward process.
All braking systems function by applying friction to counteract the forward movement of your car's wheels. This friction gradually increases resistance, ultimately bringing the wheels to a halt. In scientific terms, your brake pads are converting the car's kinetic energy into thermal energy. Disc brakes achieve this through a friction pad (also known as the brake shoe or brake line) that presses against a rotor (the disc).
Over time, the constant friction leads to wear and tear. Brake relining simply involves replacing these friction pads. It's a routine aspect of vehicle maintenance and doesn't necessarily indicate a major issue with your car.
In this article, we'll explore the process of removing old brake lines and installing new ones. But first, how should you prepare for this task? What tools will you require? Keep reading — and if your brakes are excessively noisy, it might be time to visit the auto shop.
Brake Relining Preparation
You've confirmed that the noise is originating from the front brakes, which house the disc brakes in most modern vehicles.
Before dismantling your wheels, inspect the brake caliper through its opening. Can you spot the friction material? If it's less than 1/4 inch thick, it's time to replace the brake shoes. If it's under 1/8 inch, act immediately — insufficient friction material poses a safety risk and could harm the brake rotors, leading to more expensive repairs.
If the brake rotors show signs of damage, consider having a mechanic smooth out or "turn" any deep grooves. This process involves sanding the surface to restore smoothness. However, if this has already been done, the rotors might be too thin for further use, indicating it's time for replacements [source: Buckman].
Refer to your car's owner manual to determine the minimum thickness for brake rotors. Overly thin rotors are less effective at slowing your vehicle, and replacements are generally affordable.
You should also prepare for the possibility of replacing your brake calipers. As part of a hydraulic system, they can develop leaks or corrosion over time. Since you'll already be disassembling the brakes, consider investing in new calipers.
Inspecting these components might seem excessive, but remember — anything causing unnecessary friction reduces fuel efficiency and could compromise your safety.
Before diving in, review the list of tools and parts on the following page. For a quick refresher, you might also want to revisit the components and design of a disc brake system.
Unless you own a high-performance sports car, your rear wheels likely use drum brakes. While disc brakes are far more efficient and can shorten stopping distances, enhancing safety, why don't manufacturers equip all four wheels with them? For starters, drum brakes are more cost-effective. Additionally, approximately 90% of a car's braking power comes from the front wheels. Automakers have strategically placed the superior technology where it matters most — up front [source: Memmer].
Tools for Brake Relining
As previously mentioned, brake relining is a straightforward process, and you don't need overly specialized tools to do it correctly. Here’s a list of essentials to gather before starting:
- A reliable method to lift your car. This includes two jack stands — not hydraulic jacks — or a floor jack. Ensure it’s sturdy enough to support your vehicle safely for several hours.
- A tire iron or spinner
- Brake pad grease (also known as caliper slide grease)
- The crucial new brake pads
You might also consider having the following items on hand:
- A vise grip, channel lock, or C clamp
- Heavy-duty gloves
- A dust mask
- A micrometer
Depending on your workspace and how prone you are to accidents, you might also want to keep a few disposable plastic cups and a Sharpie® handy. These can help you organize, separate, and label bolts and fasteners as you disassemble the brake components.
Lastly, if the brake pads have significantly worn down (to 1/8 inch or less), inspect the discs for signs of damage. Indicators of potential issues include:
- an uneven surface
- a dull surface
- grooves or gouges in the metal
- variations in thickness (even minor ones can be problematic; verify with a micrometer)
- warping
- cracks
- a diameter that meets or exceeds the maximum limit for that rotor (usually stamped on the disc)
- differences in thickness between the rotors on the front wheels [source: Memmer]
If any of these signs are present, it’s time to replace the discs. Replacement brake rotors are readily available at auto parts stores.
On the next page, we’ll dive into the first major step: removing the old brake pads.
It’s a well-worn saying, but it holds true: having the right tools is essential for this — or any — auto maintenance task. Avoid using subpar tools or repurposing tools for unintended uses. High-quality tools are an investment in your home auto workshop, making the job easier and ensuring safety for both you and your vehicle.
Removing Old Brake Lines
Start by parking the car and lifting the front end with a jack. Don’t forget to engage the parking brake. If you’ve been driving recently (e.g., to the auto parts store), be cautious — engine components may still be hot enough to cause burns.
Next, use your tire iron or spinner to remove one of the front wheels. Detach the brake caliper, which will likely require removing bolts. Keep the bolts organized in clearly marked areas to ensure you know which ones belong to which parts. Slide the caliper off the rotor.
The brake pads are located inside the caliper. Depending on your vehicle, you’ll find bolts, springs, or clips securing the pads to the caliper. Remove these fasteners.
You’ll observe that the new brake pads are thicker than the old ones. This means you’ll need to adjust the piston to fit the new thickness. Open the piston fully, positioning it closer to the car’s center than the wheel. While you might manage this by hand, if it resists, use a vise grip, channel lock, or C clamp to push it back. If using a C clamp, ensure the piston’s surface is protected, and note that a stubborn piston could indicate caliper issues [source: Memmer].
Opening the piston forces fluid back into the hydraulic system. Professional mechanics often reduce fluid in the piston’s reservoir before lifting the car. Skipping this step may cause the reservoir to overflow.
Now, if necessary, proceed with replacing the rotor.
Before installing the new brake pads, apply brake pad grease to the side of the pads that will face away from the rotor.
You’re more than halfway through the process. To learn how to install the new pads and test the car on the road, continue reading.
Inspect the caliper closely. Is it corroded or leaking? Calipers aren’t designed to last indefinitely. Faulty calipers can result in poor braking performance, rotor damage, and reduced fuel efficiency. If you’re already replacing the brake pads, it might be wise to consider replacing the calipers as well. However, if there are no obvious issues, you may not need to take this step.
Installing New Brake Lines
Position the new brake pads onto the caliper. Reattach all clips, bolts, and anchors, ensuring they are evenly tightened. Inconsistent tightness can cause rotor damage over time.
Next, slide the caliper back onto the rotor and reattach it securely.
Now, repeat the entire process for the other front brake. Don’t forget the crucial step of reattaching the wheels.
It’s time to take the car for a test drive. Professionals call this process "burnishing" the new brake pads [see sidebar]. The heat and friction generated during driving help the new pads perform optimally. However, avoid excessive heat until the pads are fully conditioned.
- If you removed brake fluid from the piston reservoirs, refill it. While some mechanics suggest replacing the brake fluid, reusing the old fluid won’t cause significant issues.
- Avoid overheating the brakes. Refrain from sudden stops and try not to come to a complete halt until the burnishing process is complete. After finishing, allow the car to cool down.
- Gradually accelerate to around 45 mph, then gently brake to about 5 mph. Maintain this speed for a minute before repeating the acceleration and braking process. Perform this cycle at least ten times.
- Choose a quiet road for testing and leave extra stopping distance. You’re testing the brakes because there’s always a chance, however small, that they might not function as expected.
- Listen carefully while driving. Some squealing is normal as the brakes adjust to the new pads, but if it continues, double-check your work. Ensure all clips and bolts are evenly tightened.
Why does driving heat enhance the performance of your new brakes? The friction pad on the new brake shoe contains specific resins that are activated by heat. These resins rise to the pad’s surface, optimizing braking efficiency.
