There’s a reason we’re instructed to gaze in both directions before crossing the street. This pedestrian should not have left the sidewalk. Obviously, she cannot see you. So you apply the brakes, causing her to retreat. Except that high-pitched screeching noise does not appear to originate from the pedestrian. It emanates from your vehicle.
It sounds like your brakes may need to be relined. Brake relining is one of the most common types of brake maintenance, so you need not fret. It’s a straightforward procedure.
All brakes function by introducing friction to the wheels’ forward motion. The friction makes it increasingly difficult for the wheels to move forward, so — you guessed it — they stop. In terms of physics, this indicates that your brake pads are converting the vehicle’s kinetic energy into thermal energy. Disc brakes accomplish this by pressing a friction pad (also known as the brake shoe or brake line) against a rotor (the disc).
All of this friction eventually causes erosion. Relining brakes simply involves replacing the friction pads. It’s a normal part of driving, and it doesn’t necessarily indicate a major problem with your vehicle.
This article will examine how to remove the old brake lines and install the new ones. However, how do you initially prepare for this procedure? And what equipment will you need? If your brakes are extremely noisy, it may be time to walk to the auto shop.
Brake Relining Preparation
You’ve determined that the noise is indeed emanating from the front brakes, where most late-model automobiles feature disc brakes.
Examine the inspection opening in the brake caliper prior to disassembling the wheels. Are you able to see the line of the friction material? When there is less than 14 inch of friction material remaining on the brake shoes, it is time to replace them. If there is less than 1/8 inch of friction material, there is no time to waste; the lack of friction material could be hazardous. And it may be causing damage to the brake rotors, which is more costly to repair.
If there is damage to the brake rotors, you may wish to have a mechanic smooth out (or “turn”) any deep gouges in the discs. Essentially, this procedure involves sanding away the scars to create a new, smooth surface. However, if you have already done so, the discs may no longer be usable. Consequently, they should probably be replaced. [source: Buckman.
The minimum thickness of your brake rotors can be found in your vehicle’s owner’s manual. Thin rotors are less effective at slowing you down, and replacements won’t cost you a fortune.
Additionally, you may wish to be ready for the possibility of replacing your brake calipers. As a hydraulic system, they are susceptible to leaks and corrosion under normal conditions of use. Consider purchasing replacement calipers, given that you will be disassembling the brakes anyway.
Checking all these other components may seem excessive, but keep in mind that anything that adds unnecessary friction to your ride will decrease your fuel economy. Additionally, your safety may be compromised.
Before you begin, review the tools and parts list on the following page. As a refresher, you may also wish to review the disc brake’s components and construction.
Tools for Brake Relining
As we’ve mentioned, brake relining is a relatively simple process that doesn’t require any fancy tools. Before beginning, you should have the following materials on hand:
- A safe way to jack up your vehicle. This necessitates the use of two jack stands, not hydraulic jacks, or a floor jack. You need something sturdy enough to hold your vehicle securely for the duration of your work, which will last several hours.
- A tire iron or spinner
- Brake pad grease (a.k.a. caliper slide grease)
- The essential new brake pads
You may also wish to consider:
- The use of a vise grip, channel lock, or C clamp.
- Heavy-duty gloves
- A dust mask
- A micrometer
Depending on the location of your work and the likelihood of accidents, you may also want to bring along a few disposable plastic cups and a Sharpie®. As you disassemble the brakes, these can be used to contain, separate, and label the bolts and other fasteners for the different brake components.
Lastly, if the brake pads have worn down significantly (to 1/8 inch or less), the discs should be inspected. Warning signs include:
- an uneven surface
- a metal’s surface
- is pitted or grooved by abrasion.
- differences in thickness (even tiny ones can be problems; check using the micrometer)
- The warping
- have a diameter that meets or exceeds the rotor’s maximum (which should be stamped on the disc itself)
- Variations in rotor thickness between the two front wheels [source: Memmer]
If any of these signs are present, it is time to replace the discs. You can find replacement brake rotors at your local auto parts store.
On the following page, we’ll examine the first major step: removing the old brake pads.
Removing Old Brake Lines
Priority comes first: Park and jack up the front of the vehicle. Don’t forget to set the parking brake. And if you’ve been driving for a while (for example, to the auto parts store), keep in mind that engine components may be hot enough to cause burns.
Remove one of the front wheels using your tire iron or spinner. Removable the brake caliper. This will probably require the removal of bolts. Remember to store bolts in clearly labeled areas, so you can determine which bolts belong to which parts. The caliper must be slid off the rotor.
The brake pads are situated within the caliper. Depending on the vehicle, the pads may be attached to the caliper with bolts, springs, or clips. Unfasten the fasteners.
The new brake pads are noticeably thicker than the old ones. Therefore, the piston must be adjusted to accommodate the new thickness. Release the piston. When fully opened, it will be closer to the car’s center than the wheel. You may be able to open it with your bare hands, but if it resists, use a vise grip or channel lock to force it open. It can also be opened with a C-clamp. Get the clamp’s lips inside the piston, and then release the clamp. If you choose this route, however, you must protect the piston’s surface. And be aware that a tight piston could indicate caliper issues. [source: Memmer].
When the piston is opened, fluid is forced back into the hydraulic system. Before raising the vehicle on jacks, professional mechanics take the precaution of lowering the fluid level in the piston’s reservoir. If you disregard this step, the reservoir may overflow.
If you are replacing the rotor, it is now time to do so.
Before installing new brake pads, grease them with brake pad grease. Place it on the opposite side of the new brake pads from the rotor.
You’re well past the halfway point. Read on to learn how to install new brake pads and road test the vehicle.
Installing New Brake Lines
Install the replacement brake pads on the caliper. Reattach the clips, bolts, and anchors so that they are as uniform as possible. Variations in tightness can eventually cause rotor damage.
Next, reattach the caliper to the rotor by sliding it back onto it.
Repeat the entire procedure for the second front brake. And, most importantly, reattach the wheels.
Let’s now get this dog on the road. Professionals refer to this procedure as “burnishing” [see sidebar] the new brake pads. The heat and friction of driving are what optimize the performance of new brake pads. Nonetheless, this necessitates avoiding excessive heat before the pads are prepared to handle it.
- Replace any brake fluid that was drained from the piston reservoirs. Some mechanics recommend replacing the brake fluid as part of this process, but you won’t ruin anything by reusing the old fluid.
- Again, do not let the brakes overheat. Do not brake abruptly, and avoid coming to a complete stop until the burnishing is complete. And when you’re finished, do not immediately drive the vehicle again. Let it cool.
- Gradually accelerate to approximately 45 mph. Then, gradually slow to approximately 5 mph. Drive at that rate for approximately one minute. Then, gradually accelerate to 45 mph and then gradually decelerate. At least ten times, repeat the process.
- Choose a road that is relatively untraveled and leave more stopping distance than you believe you’ll need. You are inspecting the brakes due to the remote possibility that they may not function.
- As you drive, listen. As the brakes adjust to the new pads, you may hear a squealing sound. It’s likely nothing to worry about, but if it persists, you might want to examine your work more closely. Ensure that all clips and bolts are attached with the same degree of tightness.