Brakes squeak because the friction produced by the contact between the brake pad and the rotor make noise when a certain frequency is reached. You can think of this like a violin being played or when you rub your wet finger around the rim of a glass.
When two surfaces contact each other and are rubbed together, vibrations are produced depending on which string is played – how tight it is – or how full the glass is.
The same concept applies to brakes depending on several factors.
What Causes Brakes to Squeak?
The reality is that eventually, most brakes will end up squeaking at some point in time because conditions are constantly changing when you drive, and even when you don’t.
Anything that causes the frequency of the vibrations within the exterior braking mechanism to be altered will affect if and when your brakes squeak. Most of the things that cause brakes to squeak are not preventable at face value, but many are fixable to differing extents.
Here are the most common causes for squeaking brakes:
Dirt and Debris
Because your wheels are always moving, there is a good chance that at least some road debris will get kicked up onto your car. The potential also exists for this debris to occasionally get kicked into the brakes.
Though your brakes are usually well-protected, dirt and debris are everywhere you go. Small rocks and dirt accretion, especially when they get in between the rotors and pads, can get ground into the rotors or pads and effect the vibrations caused by the friction of the brakes, thus causing your brakes to squeal.
In addition to regular road dirt, brake dust can also contribute to squeaking. Brake dust results from brake pad material slowly wearing down as the brakes are used and contact is made with the spinning rotors. Brake dust can be particularly tricky to remove and can easily accumulate on pads and other braking components.
Brake Pad Materials or Brake Rotor Type
Brake pad materials have improved with technology. Better, more efficient materials are often used in newer vehicles that were not used twenty or thirty years ago. Many of these pads are made from harder materials as well, and with that often comes some amount of brake squeaking.
Along with the hardness of the brake material, the material of the pad itself can also affect its noise. Semi-metallic brake pads are known for being especially noisy. This is because they contain metal fibers within the pad material.
Even though these fibers are small, it still means that on some level, there is metal to metal contact within your brakes, giving them their reputation for being squeaky at times. These types of pads do offer superior stopping power but also tend to wear the brake rotors faster than other types of pads because of their metallic content.
Cars equipped with high-performance braking systems are also known to have squeaky brakes. Both the high-quality brake pads and even the type of rotor contribute to the noise.
Vented or drilled brake rotors are often noted to contribute to brake noise, and high-performance brake pads often sacrifice a reduction in brake noise for the best stopping materials possible.
Extreme weather conditions can wreak havoc on many different components of your vehicle, especially if your vehicle is not garage-kept or you just happen to get caught in some kind of storm. Even passive weather like extreme cold or extreme heat and humidity can have an effect on your brakes.
Rain, snow, and ice can affect the amount of lubrication present on your brake pads and rotors. If they get wet, your brakes will be more prone to squeaking in addition to hampering your vehicle’s braking ability.
Additionally, extreme heat, cold, and humidity can microscopically expand and contract various materials, making brake squeaking more common.
We have already examined how weather and moisture it produces can cause brake squeal, but standing water can do the same by splashing onto your brakes.
Squeaking because of driving through a puddle can be briefly annoying. Usually, as you apply the brakes and the water is skimmed off the rotors, the squeaking will go away, but if the puddle is large enough, your vehicle’s brakes may not work properly because of the additional lubrication on brake surfaces.
This is just one of the reasons that safety professionals and meteorologists advise not to drive through standing water.
It is common for most modern cars to weigh between three thousand and four thousand pounds depending on how large they are, and large pickup trucks can weigh more than six thousand pounds.
Manufacturers would not equip brakes to a two-ton vehicle that were only designed to handle one ton of weight because of safety ramifications. Therefore, manufacturers equip vehicles with brakes that are proportionate to the vehicle’s weight.
Often times, they will even equip brakes that are able to handle much more weight or more extreme conditions as in performance cars and large trucks that are typically meant to haul large loads.
Despite this, adding extra weight to the vehicle or using the brakes for an extended period of time can push the braking system close to the edge of its design parameters. Even if brakes can handle the additional weight of a trailer or the high speeds of track racing, it does not mean that these greater loads are just as easy to handle when the vehicle is operated under normal conditions.
Adding weight, adding speed, and therefore, adding work that the brakes need to accomplish can make them squeak. This does not necessarily mean the brakes will fail, but the additional friction and heat generated by the increased loads can change the conditions and make the brakes complain.
Chances are that you woke up one morning, walked out to your vehicle, and panicked a little because your brakes looked a little "rusty." This is actually normal, and it is because of the oxidation that occurs on steel – a common brake rotor material – from overnight moisture or from sitting for a long period of time.
If you haven’t noticed any rust on your brakes, you may have noticed some terrible grinding or squeaking noises coming from your brakes as you pull out of your driveway first thing in the morning. This happens because of the natural environmental factors that affect your vehicle as it sits. The longer it sits, the greater the chances of your brakes squeaking or making other noises.
Worn Out Pads
Often, the first thing people think about when they hear squeaky breaks is that the brakes need to be fixed. That may be true if there is constant squeaking or squealing.
Most braking systems have a small metal peg or pin that contacts the brake rotor when the pads get too low, similar to a needle on a record player. Some of these systems are designed to make a squealing noise even when the brakes are not applied, but most low pad systems only squeal when the brakes are pressed.
If you suspect that your brake pads are low because of consistent brake squeaking, you should consult a professional.
Should You Be Worried if Your Brakes Start to Squeak?
The short answer to this question is no.
There are many reasons why your brakes could be squeaking that your mind shouldn't immediately entertain the idea of brake failure, especially if you have a fairly new vehicle.
Brakes are designed to stop your vehicle, and unless there is something very wrong, you will still be able to stop your vehicle, despite any noises you hear.
There also is a difference between brake squeaking and brake squeal. You might think of this by comparing two different scenarios:
If you have ever gone to a basketball game, you have probably heard the constant squeaking of players’ shoes on the court. This is simply because the soles of the shoes are contacting the floor as the weight of each player is transferred onto the ground. It can get annoying if you are sensitive to sound, but the noise is just a result of the stickiness of the shoes gripping the court.
On the contrary, you have probably cringed when hearing someone’s fingernails slide down a chalkboard. Even thinking about that noise probably gives you shivers.
This is the difference between brake squeaking and brake squealing. The fingernails against a chalkboard are much more grating noise and are more persistent. This is more akin to what a low brake pad indicator would sound like as opposed to normal brake squeaks every once in a while.
What Can You Do to Fix or Prevent Squeaking Brakes?
There are many ways to fix brake squeaking, but there are few ways to prevent it altogether. This is because most people have to drive their vehicles, and exposing them to the environment exposes a vehicle to numerous elements that naturally can cause squeaky brakes.
That being said, there are five main ways to fix or prevent brake squeaking, even if it is just an annoyance rather than a problem with the brakes themselves:
Change Your Brake Pads and/or Rotors
The easiest way, but possibly the most expensive way to get rid of squeaky brakes is to change the pads, rotors, or both.
There are three main types of brake pads: Ceramic, semi-metallic, and non-asbestos organic. Ceramic brakes are reported to be the quietest type of pad while semi-metallic is often the noisiest. The downside to ceramic brake pads is that they are often the most expensive type of pads.
You may also want to explore changing your rotors if you have consulted a professional, and your brake pads are not the issue. Brake rotors can warp and ridge, especially if there is a bit of debris that lodges in between the pad and rotor or if your previous pads were excessively worn.
If you do go to change your brake pads, rotors, or both, and you do find that debris is lodged between the pads and rotors, you may be able to remove it and avoid changing anything if you catch it before any damage is done.
Keep Your Vehicle Sheltered
Not everybody is able to keep their vehicle in a garage, but the more you are able to control the environment in which your vehicle lives, the less chance you will have of experiencing squeaky brakes.
Keeping your vehicle out of the rain, snow, heat, cold, and humidity will prevent the typical early morning brake squeaking.
Drive More Conservatively
An easy way to prevent squeaky brakes is to drive more conservatively. Aggressive stopping, frequent stopping, and adding any excess loading to your vehicle are all small ways to prevent squeaking.
Sometimes, pulling a trailer is a necessity, especially if you do it for a living, but anything that makes your vehicle work harder than it usually does could cause squeaking.
Use a Brake Lubricant
Brake lubricant is not designed to be put directly on the brake rotor but rather on the edges of the brake pads, brake pistons, and caliper bushing.
You should never put brake lubricant where the brake pad would contact the rotor as you would effectively prevent the brakes from working properly. Brake lubricant is designed to reduce the vibrations within the braking system, and therefore, prevent squeaking.
Always read the instructions on your chosen brake lubricant to ensure proper application.
Use an Anti-Squeaking Adhesive
Like brake lubricant, anti-squeak brake adhesive is designed to reduce brake squeaking. Unlike brake lubricant, adhesive absorbs the vibrations produced by friction. It is usually applied to the back of the brake pad where it attaches to the caliper.
The answer to why brakes squeak is fairly straightforward. The vibration caused by the brake pads contacting the rotors produces sound in the form of squeaking, depending on several different factors.
Anything that affects the frequency of the vibrations like weather, dirt, or the type of brake pads on your vehicle can cause the squeaks you hear. Squeaking isn’t always a sign of brake failure and can be quite normal, but now that you know more about what causes brakes to squeak, you are now better prepared to respond appropriately when it happens with your vehicle.