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Squeaky Brakes? Grinding Noises? What it Means, and What to Do

Mia Bevacqua
February 13, 2018

brakes

Brake noise is like fingernails on a chalkboard. Every time your vehicle comes to a stop, the brakes squeak, grind or squeal — it’s so annoying. But more important than that, brake noise can indicate a serious safety problem that could affect your car’s ability to stop.

If your brakes are making a racket, it’s a good idea to have a mechanic check them out as soon as possible. 

How your brakes work

Brakes bring your car to a stop — we all know this. But how does it happen?

There are two basic types of braking systems: disc and drum. Most vehicles have disc brakes on at least the front axle, and many have discs all the way around. 

Disc brake system components:

  • Pads
  • Rotors
  • Calipers

Drum brake system components:

  • Shoes
  • Drums
  • Wheel cylinders

Both types of systems have a master cylinder, where hydraulic pressure is created when you press the brake pedal. Pressing the pedal forces the pressurized brake fluid through a series of brake lines and hoses to the wheels. 

At each wheel, the brake fluid forces a hydraulically operated caliper to push the brake pads against the rotor. In a drum brake system, hydraulic pressure causes the wheel cylinder to push the brakes shoes against the drum. Either scenario slows down the vehicle and eventually brings it to a stop.

Common noises

When brake issues occur, they usually cause the following noises:

  • Grinding
  • Squealing or squeaking 
  • Clattering or rattling

Let’s look at what causes these noises, and what to do about it. Keep in mind that some brake problems can cause more than one type of noise, depending on the vehicle design and how the parts are worn.  

Get it diagnosed by a professional
 

Grinding

If your brakes are grinding, they need immediate attention. Typically, this means the brake pad or shoe material is worn away, leading to metal-to-metal contact. This is both dangerous to drive with and can create more expensive repairs. Here are the most common causes of grinding brakes:

Worn brake pads or shoes: Brake pads and shoes consist of friction material mounted to a metal backing plate. When the pads and shoes wear down, it can result in a metallic grinding noise, as the backing plate starts making contact with the rotor or drum. Brake pads also have a metal wear indicator that drags on the rotors when the pads are worn out. This will make a grinding or squealing noise.

Solution: Your brake pads or shoes need to be replaced. When your mechanic does this, he or she will also visually inspect the rotors or drums for signs of damage such as cracks, scoring and heat spots. The mechanic will also measure the thickness of the rotors or drums to see whether they can be machined or if need to be replaced. 

Sticking caliper or wheel cylinder: A sticking caliper can cause the pads to be continuously forced against the rotor, creating a grinding or squealing noise. The same is true for a wheel cylinder that’s stuck, forcing the shoes against the drums.

Solution: In some cases, removing the caliper and greasing its slides may help. If not, the technician will replace the caliper or wheel cylinder and bleed the brakes. You’ll also want the pads and rotors, or shoes and drums, inspected for damage and replaced as needed.

Squealing or squeaking  

Squeaking sounds could just mean you’ve got cheap brake pads or hot brakes, or they could be a sign of a bigger problem. Brakes that are overheating can cause a light squeaking, especially when the brakes are still cold. But if your brakes are consistently squealing, you should get them inspected. Here are the most frequent causes:

Pad or shoe friction material: In some cases, poor-quality friction material may cause a squealing noise. This is especially common in semi-metallic brakes.

Solution: Replace the brake pads with ones of better quality. Ceramic brakes are a good choice, as they typically make very little noise — though they tend to be a little more expensive.

Worn brake pads: As mentioned above, brake pads have a metal wear indicator that drags on the rotors when the pads are worn out. This will make a squealing or grinding noise.

Solution: You need to have your brake pads replaced.

Foreign debris: Occasionally, debris such as small stones may get trapped between the pad and rotor, or shoe and drum. This can cause a grinding or squealing noise.

Solution: The mechanic will inspect the brakes and disassemble them as needed. The debris will be removed and any damaged components will need to be replaced.

Glazed rotors or drums: Brake rotors and drums wear over time, resulting in a glazed or rough finish. As a result, the brakes may make a squealing or screeching noise.

Solution: If the rotors or drums are still thick enough, they typically can be machined to improve the finish. If they’re not, they’ll need to be replaced. Either way, they should first be inspected for damage such as cracks, scoring and heat spots. 

Lack of lubrication on drum backing plate: In a drum brake system, the shoes and drum mount to a backing plate. If the backing plate isn’t lubricated at the shoe contact pads, you may hear a squealing noise.

Solution: Remove the drum and shoes and lubricate the backing plate.

Clattering or rattling

If you hear clattering sounds when you hit the brake pedal, it usually means that something is off kilter in you braking system. You might also feel a pulsing sensation through the pedal or steering wheel. An inspection is in order. Here are some common causes:

Warped rotors or drums: Brake pads make uneven contact with warped rotors. This can result in a clattering noise, typically accompanied by a pulsating brake pedal and, in some cases, a vibrating steering wheel. The same is true for drums that are worn unevenly, preventing the shoes from making proper contact.

Solution: You should have the rotors measured for minimum thickness, variations in thickness, taper and runout (which causes the pedal pulsation). In a drum brake system, the drum diameter should be measured and checked for an out-of-round condition. Have the rotors or drums machined or replaced as needed.

Damaged, missing or loose hardware: Anti-rattle clips, shims and pads are used to secure the brake pads inside the calipers. Similarly, brake shoes are secured to a backing plate using a collection of springs and retainers. If any of these bits of hardware are missing, you might hear a rattling or squeaking noise.

Solution: You’ll need to get missing hardware replaced or reinstalled. If more lubrication is needed, apply brake grease where the hardware contacts the brake caliper.

Get your brakes checked

Even if you don’t hear a problem (or feel one), your brakes should be inspected at least once a year. How often you need to get them replaced will vary depending on your car and your brake usage.

Remember, brakes are the most important safety feature on your car, and if something seems wrong with them, get your car inspected by a professional technician immediately.

Mia Bevacqua

About the Author

Mia Bevacqua is an automotive expert with ASE Master, L1, L2 and L3 Advanced Level Specialist certification. With 13-plus years of experience in the field, she applies her skills toward writing, consulting and automotive software engineering.

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