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What Do Squeaky Brakes Mean?

By Autolist Staff | March 28, 2019

Squeaky brakes are an incredibly common car problem, and it doesn't always mean that your brake pads are on their last legs. If you're hearing brake noise on your vehicle, don't rush out for a brake job just yet. There are some reasons for brake squeal that aren't terribly serious, including overnight moisture and cold weather. Let's take a look at the benign and not so benign reasons that your brakes are making a squeaking noise.

What Causes Squeaky Brakes?

In short, the squeaking sound is the result of friction between the metal of your brakes, the brake pads and possibly some foreign material between them. The type of squeak you hear depends on the condition causing it. The squeak might be soft or it might be loud and shrill. It might be one high-pitched note or it might sound like sheet metal ripping. The latter sound is one you need to immediately pay attention to as it is the most indicative of a serious problem.

What Are Some Benign Reasons For Squeaky Brakes?

  • Dust, sand, grit getting into your brake system can cause squeaking

  • Cold weather might cause squealing

  • Moisture like snow or heavy rain can result in a thin layer of rust that will disappear after using the brake pedal a few times

  • Hauling heavy loads causes the brakes to be under more pressure, which results in heat, swelling parts and possibly squeal

  • Straining during a long downhill drive can cause squealing due to heat

  • Hard brake pads often found in newer cars may squeal

  • Semi-metallic brake pads also tend towards squeaking

  • Overnight moisture can get into the brake system and cause squeaking until it wears off

When Squeaking Brakes Are Serious

As previously mentioned, the ripping sheet-metal sound is not a good sound to hear from your brakes. Before you hear that sound though, you'll likely hear some type of squealing, which comes from a safety built into many brake pads. It's a small bit of spring steel that scrapes the brake disc when the pads begin to reach their limit of wear. If you ignore this sound and don't get new pads, eventually the steel safety friction material wears down and braking will result in the ripping sheet metal sound. This is the sound of your brake rotors scraping the metal backing plates and it will cause serious damage.

Types of Brakes

It's also important to know that there are two types of brakes you might find on vehicles. Disc brakes are by far the most common on modern cars. They function by having a brake pad press against a disc, also called a rotor, to slow or stop the car. The brake wear indicator squeak only happens on disc brakes. High metal pads and overnight moisture are also disc brake problems. Drum brakes are more likely to be found on older vehicles, but sometimes they're put on the rear wheels while the front wheels have disc brakes. Drum brakes work by having a brake shoe pressing against a hollow drum. You might hear a squeaking sound from drum brakes when the contact points between the shoe and the backing require lubrication.

Stopping the Overnight Moisture Squealing Sound

This sound happens when outside moisture collects on the rotor surface. This creates a filmy rust layer, which the pads then scrape against when you first start braking after the car has been sitting. Unfortunately, this type of brake squeak can only be prevented if you store your vehicle in a garage where it is not exposed to moisture.

Avoiding High-Metal Pads

All brake pads do contain some amount of metal, but there are cheap brake pads out there that have way higher amounts of metal. These pads have big metal chunks embedded into the material. Needless to say, these heavily metallic pads scrape on your rotor and makes squealing sounds. Unfortunately, these pads can last as long as 40,000 miles, so if you install these on your car, you'll be hearing that sound for a while. Avoid this by buying quality brake pads that have more organic material such as resin, rubber, fiber and the like.

Types of Brake Pads

There are three main types of brake pads: semi-metallic, non-asbestos organic and ceramic. Each has its pros and cons. Semi-metallic pads have the most stopping power and are able to conduct heat away from the rotor. However, they do have a tendency to make noise, are susceptible to rust and can cause too much rotor wear. Non-asbestos organic pads, sometimes called NAO, are less noisy and cost less than semi-metallic pads. They contain organic fillers that reduce both heat and vibration. The main downside is that the pads wear down faster. Ceramic pads are the most expensive type and they come in second in terms of stopping ability. The main benefits of this type are that they are quiet and don't rust.

Lubricating Drum Brakes

If your vehicle has drum brakes and you hear a squeal, it's a good warning sign that your brakes need lubrication. Once the contact points no longer have lubrication, the metal starts to rust. This causes the shoes to scrape on the backing plate and thus the squeal. Repairing or preventing this noise involves using either an anti-seize compound that can withstand high temperatures or Moly Paste 60, which is a lube for the back of the pad or shoe as well as for contact points.

How to Fix Squeaky Brakes Through Driving

If your noisy brakes are due to the driving conditions mentioned at the beginning, then you can mitigate them by changing your driving habits. For example, while going down a steep grade, you can downshift to let engine compression slow you down instead of your brakes. Keeping a safe driving distance between vehicles in stop and go traffic will keep you from having to stomp on the brakes suddenly. You can also downshift and roll in this situation. If your brakes squeak when you haul heavy loads, you might consider reducing your load weight to lessen the risk of overheating.

Brake Noise FAQ

  1. Why are my new brakes squeaking? If you just put on new brakes and they're squeaking, it's most likely from lack of lubrication due to mechanic oversight, or it might be due to having brakes with high metal content.

  2. What causes a grinding noise? Depending on the severity, this might be due to totally worn pads, overnight rust or rocks getting stuck between the rotor and the backing plate.

  3. How much is a brake job? Depending on what exactly needs to be replaced, a brake job might cost anywhere from $150 to $650 for each axle.

  4. Can brakes squeal when not being pressed? Brakes can squeal without being applied, and this usually happens when the brake pad wear indicator is scraping the rotor.

  5. Do new brake pads need to be broken in? New brake pads do not have a breaking in period. They should function normally from the very beginning.

  6. How long do a car's brakes last? Depending on how you drive and the conditions, they can last as long as 100,000 miles or as little as 15,000.