Solving Brake Problems
Disc brakes have been around for some time now. They were first developed in the 1890s but didn’t see mass production till about 1950 in the U.S. The principle is fairly simple. You have a brake caliper that houses the brake pads and caliper piston(s). When the brakes are applied, hydraulic pressure is exerted on the back of the caliper piston and the brake pads make contact with the brake rotor, thus converting the motion of the vehicle into heat. In its simplest terms, brakes turn speed into heat.
Disc brakes are commonplace on the front wheels of modern vehicles, and can also be found on the rear wheels of many other vehicles. The design of the front and rear disc brakes might differ, but in operation, they are virtually the same. The exception with rear disc brakes is that many times the parking brake is part of the rear caliper assembly. We’ll get into that more in the section on rear disc brakes. For now, let’s talk about some of the common problems with disc brakes.
This goes for drum brakes as well as disc brakes. The #1 cause of brake noise is the friction material itself. I’ve also come to learn that the backing has a lot to do with brake noise as well. If you purchase bargain brake pads or shoes, expect them to be noisy. These brake pads will stop your vehicle, but they won’t stay quiet. It doesn’t matter what kind of tricks you throw at them, or how much goop you put on them, they’re still going to make noise. Cheap friction material is just that — cheap.
If you have to put anything on the brake pad to keep it quiet, it’s not a good brake pad. Yes, some pads require shims and moly grease installed out of the box, but that’s different than the myriad products out there designed to keep brakes quiet. If you’ve installed pads that aren’t keeping quiet, getting rid of the noise might not be as simple as just replacing the brake pads, especially if they’ve been on there for a while. If that’s the case, you might also have to machine the rotors before installing better brake pads. We’ll talk more about the machining process later in the article.
Bottom line, if you’re going to put brake pads on your vehicle, get quality, name-brand pads. You’ll thank me later when you don’t hear anything and your vehicle stops on a dime. You’re already saving money by doing the work yourself, so why not invest in a good set of pads for the best possible result?
Noise can also be caused by more than just the pads themselves. Many brake pads come with a wear indicator. This indicator is designed to make contact with the brake rotor when the brake pads have reached their service limit. This is often a small metal tab that sticks out from the brake pad. When the pad gets worn, this metal tab comes into contact with the rotor and makes a very loud noise.
This is designed to make you notice that you need to service your brakes. You often hear this noise when backing up and the brakes are not applied. If you hear this noise, inspect the brakes; you might find that they’re worn and in need of replacement.
Some high-end vehicles use an electronic indicator to warn the driver when their brake pads are at their service limit.
On these systems, you might not hear any noise, but you’ll see an indicator on the dash that advises you to inspect your brake pad wear.
Another cause of brake noise is debris getting caught between the brake rotor and the brake pads. This often causes a scraping or sometimes even a grinding noise. The debris can be small rocks or small pieces of rust. This often happens after a wheel has been removed and something in the suspension or brakes has been serviced. Small bits of rust get knocked loose and end up stuck between the brake caliper and rotor. So if you or someone else has done work on your vehicle lately that required removing the wheels and you now have a scraping noise as you drive, remove the wheel(s), clean and inspect the brakes, then recheck for the noise.
A similar issue to debris is the splash shield coming into contact with the brake rotor. The cause of this is similar to what was listed above. Usually someone has gone in there and done some type of service and slightly bent the splash shield. This problem is easy to fix, and often, you don’t even need to remove the wheel. Just grab the splash shield and bend it away from the rotor slightly. Recheck for the noise. If it’s gone, move on with your life as a noise-eliminating hero.
Lastly, let’s talk about flash rust. This is something that often happens in humid climates. If you live in a dry climate, you might never encounter this issue. Flash rust occurs on the surface of the brake rotor (or brake drum) after the vehicle sits for a period of time. How much rust depends on how long it sits and the level of humidity in the air. After this rust forms, it can cause brake noise. It’s usually a scraping or grinding noise when you’re just coasting. Often, after a few brake applications, the noise goes away.
Sometimes flash rust can lead to a brake pulsation. This can happen after your vehicle has sat for an extend period of time in humid conditions. The pulsation comes about because under the brake pads the rust does not occur. This leaves a clean spot on the rotor.
As you apply the brakes, every time this clean spot comes around, it causes the rotor to shake or vibrate. If the rust is to this point, you might need to replace or machine the rotors to correct the problem. An easy way to spot if you have flash rust on your rotors is to simply look through the wheels. Oftentimes, you can see the rust forming right on the rotors. I will say that some rotors are worse than others when it comes to flash rust. Cheap parts yield cheap results. This is as true for brake rotors and drums as it is for anything else.
Here’s a video about finding noises in the suspension. It also covers some tips on how to track down noise due to brake-related issues.
As stated earlier, the number-one cause of brake noise is the friction material used. For that reason, it’s important to choose a quality friction material to help prevent noise when doing brake work. I can think of four main types of friction material found in brake pads and shoes: metallic, semi-metallic, organic, and ceramic. There are other friction materials, such as carbon ceramic, but those are not as common as the four I mentioned.
Each friction material has its own characteristics. For instance, metallic pads will last the longest but be the loudest and work best when they get hot. Metallic pads are great for racing applications, or at least they used to be before newer materials came along. Semi-metallics split the difference between wear and noise; they were the best of both worlds before ceramics came along. Organic pads will be the quietest, but they have a short life span and often leave a lot of brake dust on your wheels. Ceramics seem to be the best of both worlds now: They’re long-lasting, quiet, and have good wear capabilities. Thing is, they’re often expensive. When it comes to auto parts, you often get what you pay for. Stick as close to OE (original equipment) as possible and you’ll get the best results. If you use cheap friction material, expect cheap results.
At some point, you might encounter a vibration when applying your brakes. This is caused by your rotors or drums becoming warped, or out of round. When this happens and you apply your brakes, you get a vibration, either through the steering wheel or throughout the vehicle.
There is a way you can isolate where the vibration is coming from if you have the right type of brake design. While driving in an unpopulated area at a safe speed, lightly apply the parking brake. Your parking brake is connected to the rear wheels. If you apply the parking brake and you don’t feel a vibration, then your issue is likely with the front rotors. If you apply the brake and feel the vibration, then your problem is likely with the rear brakes. You cannot rule out the possibility that the front brakes are also warped, but at least you’ll know that you have an issue with the rear brakes. This will not work on all vehicles. It really depends on how the rear brakes are designed. If your parking brake is contained inside the hat of the rear rotor, this test will tell you nothing, as you would not be activating the rear caliper when applying the parking brake.
Also, if you have an electric parking brake, don’t even attempt this procedure. This is just something you can try to give you a little more information about where your vibration is coming from. Here’s a video on the process that might make things a little more clear.