Squealing or squeaking brakes are a common occurrence when you’re at the track, but when you’re sitting in peak hour traffic on your way to work or in the city for a night out, the high pitched squeal can not only be annoying but even a little embarrassing!



Common Causes of Squealing Brakes

1. Worn Brake Pads

Squealing brakes can occur for a variety of reasons, with the first and foremost being worn out brake pads. Most brake pads have a small metal finger on the side of them which protrudes about 2mm past the backing plate. Once your brake pads have worn out, the metal finger begins to contact the brake disc. This results in that high pitched squeak we’ve all heard at one time or another. The manufacturer does this so that you’re prompted to have your brakes looked at and changed.


how to tell when brake discs are worn



2. Glazed Brake Pads

The other very common cause of squeaking brakes is the pads becoming ‘glazed’. All brake pads are constructed with an optimum operating temperature range. A good road pad that would be well suited to commuting to and from work or in start-stop traffic would have a low operating temperature (approx. 0-300 degrees Celsius). Performance orientated pads operate around the 400-800 degrees Celsius range, while dedicated race pads operate from 1000 degrees Celsius and up.


When a brake pad is forced to work beyond its ideal temperature range, this can lead to glazing. The brake pads material begins to break down and crystallise or harden. This results in a surface of very similar hardness and very low friction coefficient contacting each other, producing that same squealing noise. Performance brake pads are typically made of a different compound with a higher friction coefficient. This is why they are prone to squealing at low temperatures and are known for being harsh on brake discs.


Hot performance brakes


During this glazing process, the brake pads friction material can break down causing the friction material to adhere to the discs surface. This results in a pulsating brake pedal when slowing from speed as the discs typically flat surface now has high and low spots. Contrary to popular belief this is a common cause of brake run out, and as long as your discs are not below their specified minimum thickness they can be machined or cleaned to rectify this.


Glazed brake discs



3. Stones/Contaminants

A less common cause of brake squeal (although not uncommon) is when small stones/contaminants become stuck between the brake pad and disc. It’s easily fixed by quickly removing the pads and making sure they are free of grit. However, if you leave it unattended, this can result in the stone/contaminant cutting a groove into your disc as it pushes into the disc itself.


So there you have it. An in-depth look into the reasons why your brakes may be squeaking. Think it might be time for a tune-up? Head on over to Spares Box and check out our range of brakes and our Mid-Year Mega Sale! Saving up to 20% off!



Your brake rotors will generally give you signs when they’re starting to wear too thin. The forming of a lip on the edge of the rotor is a sign, as is any glazing on the finish of the rotor. You may also feel a spongey response form your brake pedal, and vibrations under braking while driving. You can machine your rotors to restore the finish, but as this can bring them to within unsafe thickness levels (and cost a lot of time) we’d generally recommend replacing them. For more detailed information, check out this article.

Having properly functioning brake disc rotors is key to making sure you’re getting the friction you need to stop safely and effectively on the road. Brake disc rotors are essentially the discs that spin with the wheel while you’re driving. When you press the brake pedal, the brake pads compress upon the disc rotor, generating friction and converting the kinetic energy of your car’s movement into heat energy. This slows the vehicle’s momentum, bringing it to an eventual stop.


Brake disc
There’s something unsettling about this gif, but it’s the best the internet could offer. Source: Wikimedia


As you could imagine, the brake disc rotors take a tremendous amount of punishment; even more so if you’re using a high-performance, high-friction brake pad. As such, to keep your stopping power at it’s best you want to make sure your disc rotors are free of wear, and replaced at regular intervals.



How Do I Feel When My Disc Rotors are Getting Past It?


Most of the time, you’ll be able to tell how your disc rotors are going just by being a conscious driver. When the brake disc rotors are worn, the pads aren’t able to get a consistent grip, leading to vibrations that you’ll feel upon pressing the brake pedal. The same problem will also cause the brakes to squeak in some cases and produce a less responsive, spongey feeling when you press the brake pedal. Any one of these three things (along with a general drop in braking performance from what you’re used to) can all be indicators of worn brake pads.



Are My Brake Disc Rotors Too Thin?


Simply measuring the thickness of the disc rotors is a major giveaway on whether your disc rotors are starting to wear too much. Once they get past a certain point (like these ones below), they’re going to need replacing. Consult with the manufacturer of your brake disc rotors for their recommended minimum thickness. If you’re not sure, any mechanic will measure them as part of a standard check up. As the brake pad only presses against a certain part of the disc rotor, they’ll be a different width along the top than they will at the their base. This also creates a bit of a lip at the very top of the disc rotor.


Brake Disc



Machining or Replacing? The Great Trade-Off


In some cases, as you can see below, they may just need machining. This is performed by a mechanic or a specialist brake shop on a specifically designed brake lathe. During the process, a small layer of metal is machined off of the top of the disc rotor, getting rid of the grooves and exposing a fresh surface of metal underneath. This allows the brake pad to get more grip on the disc rotor, rejuvenating your stopping power. Doing this will reduce the life of the disc rotor, and also take more time than simply replacing it. For many common cars, it will generally be more convenient to throw a new set of disc rotors on.


Brake disc



Making sure your brakes are at peak performance is one of the easiest ways of keeping you and your passengers safe. If you want to simply refresh your stopping power or make the upgrade to a more performance oriented feel, fresh brake disc rotors should be one of your first steps. When replacing your pads or brake disc rotors, make sure you change your brake fluid as well, as this can be a key cause of your brakes underperforming, and no amount of part replacements will make that much of a difference if your brake fluid isn’t where it should be. You can shop our huge range of braking products here.

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