Ask Car Mechanic

Ask Car Mechanic

How To Fix It

What Causes Brake Squeal While Driving?


What Causes Brake Squeal While Driving?

Brakes play a critical role in keeping you safe on the road. Brake pads create friction with brake rotors to slow the vehicle down whenever necessary. But, despite the friction, squealing noises aren’t normal. So, why would brakes start squealing while driving?

Brake squealing can simply be the result of the brake’s design. For example, brakes have wear indicators that squeal to let you know a replacement is needed, while semi-metallic brake pads are more prone to squealing than other materials. Trapped debris between the pads and rotors can also cause squealing, as well rusted rotors and overheating from aggressive braking habits.

The following sections will show you the reasons why your brakes squeal as you’re driving. But, more importantly, you’ll also discover how to fix those causes and prevent them from happening again.

Why Do Car Brakes Squeal While Driving?

Car brakes usually function without any noise at all. So, if you hear squealing from any of your brakes, you must pay attention and troubleshoot the issue.

Here are the reasons your car brakes squeal while driving and how you can fix the problem as soon as possible:

Thinning Brake Pads

Believe it or not, your brake pads are deliberately designed to squeal when they start to wear out.

Your brake pads gradually wear out the more you use them. As they approach the end of their lifespan, they become so thin that a small part called the ‘squealer’ starts to grind against your brake rotors to create that squealing sound you hear.

That feature aims to alert you that your pads are worn out and that you must replace them as soon as possible.

This part of the brake pad’s design makes things very convenient, considering there’s no other way to monitor their condition. After all, those parts are hidden away at your wheels, away from your line of sight, and without any indicators of their condition.

How to fix it: Suppose your brake pads are squealing for the reason mentioned above. In that case, you must replace the pads with new ones. 

A fresh set of brake pads won’t just eliminate the noise but also ensure your braking system works correctly when you need it the most.

Read: What Happens When Brakes Overheat?

Trapped Debris Between Pads And Rotors

Naturally, brake squealing doesn’t just happen by design. In most cases, the squealing is also the result of a genuine problem, like debris getting trapped between the pad and the rotors.

Your wheels kick up all sorts of debris as they roll on the surface underneath. That’s especially true if you drive over trash or on unpaved roads, though the same can happen everywhere.

Despite your wheels being somewhat open, the debris can fill the gap between the brake pad and the rotor.

Then, even when you’re not applying the brakes, that debris will grind against your spinning rotor and create the squealing sound you hear from where you are in the cabin.

How to fix it: Assuming your brake components are in excellent condition, you only have to clear the debris between the brake pad and the rotor.

Depending on how bad it is, you might have to temporarily remove the wheel and brake caliper to perform a more thorough cleaning.

Read: 4 Signs Of Warped Brake Rotors (With Pictures)

Rusted Brake Rotor

The exposed positioning of your brake rotor doesn’t just leave it vulnerable to road debris. Unfortunately, that also increases its risk of experiencing corrosion and getting rusted over an extended period.

Remember: brake rotors are constantly turning as you drive. It’s only when you apply the brakes that those rotors slow down.

So, rusted brake rotors likely grind against other metal parts surrounding them. As a result, that friction generates squealing sounds you hear while driving, regardless of whether you’re applying the brakes.

How to fix it: Depending on the severity of the rust, you can resurface the rotor to continue using it without any squealing. However, you must replace all brake rotors eventually.

If you have the budget, a more comprehensive and long-term solution would be to replace the affected brake rotor with a new one. Not only will it eliminate the noise, but you also won’t have to worry about it for many years to come.

Read: Brake Pads vs Brake Rotors – What Are The Differences?

Aggressive Braking

Brake squealing can also be the temporary side effect of your aggressive braking style. To clarify, aggressive braking means applying the brakes harshly, especially at high speeds. For example, drivers who race their cars using stock brakes would fit into this category.

Remember: brakes work by creating friction that slows the wheels down. That friction converts kinetic energy, causing your brakes to heat up.

That heat is nothing to worry about under normal conditions. However, aggressive braking creates an overheating condition, leading to noises and smells coming from your brakes.

Among those noises is the squealing that you hear while driving.

How to fix it: Firstly, you can fix this problem and prevent it from happening by improving your braking habits. Gentle braking still generates heat but without overwhelming your brakes and causing squealing noises.

However, if you’re using your car in demanding situations that require aggressive braking, then you’re best upgrading the brake system to keep up. 

Heavy-duty brakes can dissipate heat more effectively, thereby preventing overheating and noises like squealing.

Read: Bad Brake Booster (Signs & Causes & Fixes)

Brake Pad Materials

Lastly, you must also consider the materials your brake pads are made of. In case you didn’t know, brake pads are made from a wide variety of materials which are also blended together.

Generally, the three types of materials for brake pads are organic, semi-metallic, or ceramic. Most cars often use semi-metallic pads made from a blend of iron, steel, and more.

Despite being so common, semi-metallic pads have one downside: they can sometimes create a squealing noise when using them.

The reason for that is straightforward. After all, the semi-metallic brake pad is pushed against the metal brake rotor. That friction can sometimes cause the squealing noise you hear, though it shouldn’t last very long.

As the noisy part of that brake pad wears away, so will the squealing noise it caused earlier.

How to fix it: If this is why your brakes are squealing while driving, there’s nothing to be fixed. That’s because the squealing noise is a natural side-effect of the brake pad material and not a sign of any real problems.

However, you can still prevent the noise in the future by being more mindful of your brake pad choices. Next time, you can switch to a brake pad with a lower percentage of metals in its materials.

That will reduce the likelihood of squealing coming from your brakes.

Final Thoughts

Your car’s brakes should never make loud noises while driving, regardless of whether you’re pressing down on the brake pedal. That’s why you should inspect your brakes if they start squealing.

Squealing can be done by design, such as with the brake wear indicators and with semi-metallic brake pads. Wear indicators squeal to inform you that you must replace the brake pads soon. Meanwhile, some parts of a semi-metallic brake pad will squeal temporarily as it pushes against your rotors.

Besides that, trapped debris, rusted rotor, and overheating due to aggressive braking can also cause the squealing you hear coming from your brakes.

Read: Warped Brake Rotors (Signs & Causes & Fixes)

Leave a Comment