People who drive cars often encounter squeaking, grinding, and scraping sounds. That may result from vibration when braking their cars, especially brake noise at low speeds. To get a clear picture, you need to understand the braking system and how brakes work. Thus, we can know why these sounds are happening and how to prevent them in the future.
The working principle of braking is friction between the braking pad and the rotors attached to the wheels, decreasing speed until a full stop. So, when you hit the brake pedal, the hydraulic fluid presses the brake pads against the rotors to generate friction and stop the car. In this braking process, you may hear noise when you’re braking at Low speed. Usually, this indicates a defect in one of the braking elements.
What are the reasons for Noise when braking at low speed?
When you hear a strange noise while braking at low speed, be aware. These sounds can be an alert for danger. It’s safe to conduct a sound check to identify the sources of these noises. In this section, we’ll be discussing the main reasons for such noises.
Worn-out braking pads: One of many reasons for strange braking sounds. The brake pads are usually manufactured from a mixture of graphite, iron, and copper. These things are bonded together to form the brake pad. When you use the brakes, the brake pads wear down until the outer metal cover touches the rotors. At that time, you will start hearing a creaking noise when braking at a low speed. So, if your brake pads have been used for a long time or are worn out, change them immediately. Or else, you can do harm to other braking elements, or they can get damaged.
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Cheap/low-quality brake pads: As we discussed before, brake pads are made from a mixture of different materials to help the pad bond. To produce the best braking pad, manufacturers combine these elements in a specific ratio to achieve optimal braking performance and eliminate noise during braking. But the cheap aftermarket braking pads are never made with this level of accuracy in selecting the materials of the pads. They always try to lower prices, which means quality decreases. Not only do they produce noisy sounds, but they also rub and scrape the surface of the rotors. So, if you’re planning to replace your braking pads, you have to choose the original ones only.
Worn-out rotor disks: Worn-out rotor disks may result from braking with worn-out pads or using a cheap/low-quality braking pad that scratches the rotor surface. So, after a while, the surface of your rotors will never stay flat as it is. Another reason for surface deflection on the rotors is washing your car and exposing them to cold water while they are still hot. This will lead to surface deflection, and you’ll hear sounds while braking and feel irregular vibrations when you press the brake pedal.
Solid items between rotor and pad: If you’re using your car in a dusty environment, it is normal for braking parts to catch dust, dirt, and grime. Besides, very tiny rocks and sands can get in between the braking pad and the rotor. These items will cause grinding noise even if you’re not using the brakes.
Parking the car for too long: Leaving your car in the garage for too long in bad weather, such as an air full of water vapor, can cause a rust layer to form on the rotors. This may also cause corrosion on the rotors, which can spread to other braking system elements.
Unlubricated caliper screws: This is also another cause of a scraping noise when braking due to a lack of lubrication on the caliper screws and bolts. If this happens to you, then you have to ask your mechanic to change them.
Broken shims: Brake pad shims are thin rubber or metal adhesive that fit between the brake caliper and the brake pad to fill small gaps that can cause noise. A worn-out shim will cause metal-to-metal contact, producing a grinding sound. And probably you will hear a knocking noise when braking at low speeds. Make sure you replace them when making any brake job.
Read Also: Brake Caliper Sticking When Hot [Causes and How to Fix it]
Types of the noise of Braking Systems
In this section, we’re going to differentiate between the different braking noises. And we’ll know how to diagnose the defect from the sound itself. Here we have three types of braking noise, and those are grinding, squeaking, and squealing
Grinding noise: This should be your wake-up call. If you hear a grinding noise from your car, stop immediately. This means the brake pad has worn out, and you are now making metal-to-metal contact between the caliper and the rotor.
Squeaking: If you hear that very annoying squeaking or scraping sound when you hit the brake pedal, it means the brake pad installed in your car is of low quality. Because it might contain a large metal flake in its mixture. So, when it drags along the rotor, you’ll hear this sound.
The best way to avoid this type of noise is to choose a high-quality braking pad. Also, if you hear a squeaking or scraping noise while you’re stopping the car with the brakes, it means the rotor is being hit by the brake wear indicator, which is making the noise. This thing named the wear indicator of the brake is a metal tab attached to the pad of the brake when the brake pads are worn out and need to be replaced. This indicator starts dragging to the rotor to let you know that you need to change the pads.
Squealing: This happens when you park your car in an outdoor or wet area. The rotors accumulate a layer of rust on their surfaces. This can cause a thumping or squealing sound when you start moving your car. This sound might have vanished after many breaks, as the rust layer will be worn away.
How to fix the brake noise problems
So, we’ve learned more about the noise we may hear from our braking system and also how to differentiate between them. Besides, we got exposed to the reason why these sounds might happen. In this section, we’ll learn how to perform some checks to know where the defective part is.
Find Loose parts: The first step is to disassemble the car’s front wheels. Then you will perform a simple check by trying to wiggle the braking calipers, pads, and rotor, and other brake components. None of these parts should be moved or wiggled by hand. If you can vibrate it with your hands, then there are a few missing, damaged, or loose clips and bolts. You need to fix those immediately. This may lead to vibrating and noisy braking.
Apply Dampening Paste: Excessive vibration from braking parts often leads to loud noises when braking. So, after taking care of missing bolts and damaged shims or clips, you may need to apply damping paste, a water-based compound that is highly effective at reducing vibrations and noise from braking parts.
Apply a thin layer of this substance on the back of the braking pad on the metal part of it between the braking pad and the caliper piston. Give the paste plenty of time to dry (2-3 hours, or until completely dry) before reassembling the brake unit. It will become sticky and darker when it is dry.
Inspect Brake Pads or Brake Shoes: Check for wear or replacement. This is the main problem that many drivers face when they’re using their cars. Many brake pads have a wear indicator that makes noise when it’s worn out. Aftermarket brake pads vary in size. This will cause a brake pad to wear unevenly. This causes the brake pads to ride the edge of the rotor, producing a rougher braking noise; you may hear grinding when braking, but the pads are fine.
In this case, you can sand the lip down and make it even, which will increase brake pad life and eliminate the noise. If you find out that you need to replace the brake pad, try to find a good one. New brake pads can make a grinding noise, too, until they wear to the shape of the rotor’s surface.
Check the brake rotors: The last check you can perform is to inspect the braking rotors. While you are using your vehicle and changing brake pads, the brake rotors may be affected. An irregular brake rotor causes the brake pad to jump and wiggle.
You need a very smooth rotor surface. So, if the rotor wear is not too deep, you may need to have your rotors machined to smooth the rotor surface. Always check the rotor’s thickness before machining because this may affect the safety of braking. But if the wear is excessive, or the entire rotor is distorted or doesn’t have a secure thickness, you have to replace the rotors as soon as possible.
Extra check: It is always recommended to check the brake oil and the brake lines after any maintenance in the braking system. You have to check its level. If it is below the marked level, then you need to fill it up with the proper oil recommended by the manufacturer, Dot 3, Dot 4, and Dot 5.
Also, check the brake fluid color. It must be clear and bright. If it’s brown, then you have to change it. You may check for leakage in the brake line, and if you find any, change it as soon as possible.
Brake Noise FAQs
Why does my car make a creaking noise when I brake?
Ans: This may be because the shims, clips, and bolts are not well-fitted, and the brake unit is wiggling during car movement. To solve this creaking sound, you may need to check that all the above parts are well-fitted and securely connected to each other. Otherwise, you have to replace the defective one.
What do bad brake pads sound like?
Ans: Brake pads always make a squealing or screeching noise that sounds like the friction of the chalk on the board. This sound means the wear indicator is dragging into the rotor, the braking pads are made from a low-quality mixture, or a metal flake in the brake pad bond is dragging into the rotor.
Why does my car make noises when I brake?
Ans: There are many reasons brakes can make noise when stopping. Some of it is related to the worn-out brake pads and the use of low-quality marked brake pads. There is another reason the clips or shims are not well installed or defective. So, vibration occurs, leading to high braking noise. Another reason is that the braking rotors have an uneven surface. This may cause noise during braking. All you have to do is inspect the cause of the sound, and early detection may prevent you from a serious danger.
How do you know if you need new brake discs?
Ans: Run a brake disc inspection. Check the discs by looking at their surfaces and noting how smooth they are, or whether they have deep grooves. Besides, try listening and feeling the braking effect. If there are any squealing sounds while braking, does the car have vibrations when braking? If all checks are positive, you need new brake discs.
Final Words:
Finally, braking noise can be an early warning sign of a serious problem. In this guide, we will learn about the causes and types of braking noise problems that may help you protect yourself from them. If you suspect a fault with the braking system, self-diagnose the issue and try to fix it yourself. But if you’re confused about the failure in your car, just go to the nearest authorized workshop and get it fixed.
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Hey, Istvan, did you check the backing plate? The backing plate typically make noise when driving. But it can also cause braking noise at low speeds.
Inspect and bar the plate away from the rotor.
Thank you; great tutorial!
I have just replaced disk rotors with stainless types; replaced brake pistons properly; leveled brake pads with sand paper; new slide pins, But in one side the noise doesn’t go away . Pads aren’t weared down, but I consider replacing them with other ( original Daihatsu) brand. Now I use Toyota brand pads.