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The brakes, many would argue, are essentially the most important part of the car, after the wheels and tires. It’s all very well getting power and propulsion from your engine, but if you have no method of slowing down or stopping, this is as good as useless.
Brakes have become drastically more effective as time has moved on. Some of the performance brake discs today can stop a car in an almost scarily quick way.
How Do Car Brakes Work?
There are two standard ways that brakes on cars can be set up – these are disc brakes and drum brakes. In modern cars, the disc brake is by far the most common.
Disc brakes have three major components to them – the disc (sometimes also called a rotor), the brake pads, and the caliper. The caliper holds the brake pads and, when you press your brake, the brake fluid causes the caliper to squeeze the pads and press them onto the disc as it’s turning. The surface of the brake pads that makes contact with the disc is made of a high-friction material. Most of the time this has a frictional coefficient of between 0.3 and 0.5. This frictional force causes resistance that slows the disc down, which, in turn, slows down the rotational speed of the wheel. This is how the car slows down. You can think of it as much the same type of brake as when you pull the lever on your bicycle.
Drum brakes, essentially, work by having a pair of “shoes” inside a drum. Pressing the brake pedal (or pulling the handbrake) causes the shoes inside the drum to push outwards onto the drum, slowing down its rotational speed from a frictional resistive force. In very basic terms, imagine a circle within a circle. For simplicity in this image, imagine the inner circle expanding, so it touches the outer circle. This is how drum brakes work to slow down a car.
Drum brakes were invented in 1900, whereas disc brakes first came out in 1902.
Which Type of Brakes?
It’s common to see all-drum systems on older cars and all-disc braking systems on new cars, although some will still opt for a disc-and-drum setup. Second-hand cars currently on the market will often be fitted out with disc-and-drum braking systems – that is, disc brakes at the front and drum brakes at the rear.
The way that manufacturers choose between what type of brake to put is relatively simple. Disc brakes provide much more “stopping power,” especially modern ones that are made of high-quality metals and work with high-powered caliper systems, ABS (anti-lock braking systems), and advanced heat dispersion techniques. Although drum brakes do not provide as much stopping force (you’ll probably feel on edge the whole time if you are driving a car with only drum brakes in this era!), they do allow for a cable handbrake. This is a simple type of parking brake, which is particularly useful when driving a standard transmission, allowing you to get the engine up to speed in neutral before you set off on a hill.
Instead of a cable handbrake, modern cars utilize an electronic handbrake – this is usually a button in the center console. This allows all four wheels to have disc brakes, maximizing the force with which a car can be brought to a standstill. However, it does mean saying goodbye to handbrake turns, the staple for any motoring enthusiast.
Why Do You Need New Brakes?
You will need new brakes when the old ones begin to stop working, as obvious as it is to say. In almost every case, this will just be down to general wear. This is absolutely fine, and brakes are designed for this.
When you get new brakes, we always recommend replacing both the disc and the pads and that they both come from the same manufacturer. This ensures that everything matches up and works perfectly together.
It’s recommended to replace your brake pads (and the disc) when pads reach about 3 mm of thickness. Many modern cars will be equipped with sensors that will cause a warning light to appear on your dashboard when this happens, but on older ones, you may need to keep an eye on it manually.
Another way to be able to tell when your brakes need replacing is when they start to screech (a different type of noise to the “squeaking” we are exploring in this article). Brake pads are built with a layer of a different sort of metal in them, so once they are worn down to this level, you’ll hear a nasty-sounding noise. Not to worry, this is specifically designed to let you know that they need changing, and as long as you act on it as soon as possible, everything will be fine.
It can sometimes be difficult to tell if you need new shoes in your drum brakes. These won’t need changing as often as your drum brakes, but it’s useful to get them serviced (this essentially just involves cleaning them up) every year or two. There may be a problem with your drum brakes if your cable handbrake isn’t working very well, if the car struggles under braking, or if your mechanic flags something up during an inspection or brake test.
What is Causing the Squeaking?
So you have a new set of brakes on your car, but you’re hearing a high pitched squeaking coming from them. What is the reason for this noise?
Well, for a start, often you’ll find that these squeaks are harmless. They are irritating and can definitely get under your skin, yes. But overall, they are generally harmless, and many will disappear with time or as you begin to drive.
We will now go through several reasons as to the cause of your squeaking brakes to help you try to understand what’s wrong.
As always, if you are in any doubt, it’s best to take your car to a professional mechanic to get them to check it out. When it comes to brakes, it’s not worth taking chances.
What’s causing the squeaking sound will be different, depending on whether it’s coming from a wheel fitted with a disc brake or a drum brake.
Causes of Squeaking in Disc Brakes
- New pads need bedding in – When your brake pads and discs are replaced, you may see the mechanic driving the car in what might appear to be an erratic manner. They might speed up and slam the brakes on several times consecutively. This isn’t just them taking your car for a quick spin. When the discs and pads are new, you’re going to need to “bed them in.” Not doing this will mean that the brakes feel spongey and like they aren’t working. Sometimes, during this early period, when the pads are creating a slight groove in the disc, you will hear more squeaking than once they have settled down.
- The high metal content of brake pads – While high metal content isn’t necessarily a terrible thing (brakes used in racing cars tend to have 100% metal brake pads fitted to them), they can make much more noise. The reason for this is the metal flakes that shave away from the pads as you use them. As these get trapped on the pad’s surface and on the disc, it causes a squeaking sound. For brake pads that make less noise, look for pads that are mainly composed of rubber, Kevlar, resin, and/or fiber. Ceramic pads are also an option for the ultimate quiet brakes, although these types can become malformed under intense heat (from heavy, sharp emergency braking).
- Moisture on the disc or pads – If you live in an area of high humidity, there is a high likelihood that the squeak you are hearing could be from moisture building up on the brake discs after your car has been stood still for a while, such as overnight. If the noise disappears very quickly after you start driving your car, this could be the reason alone. Sometimes consistent moisture exposure can result in thin layers of rust forming on the pads. These rust particles can cause the squeaking sound by themselves. You will probably be able to visibly see rust residue on your discs and pads if this is the case. Finally, rust could cause the surface of the pads to become uneven, so even if the rust has gone away, you may still hear the squeak because of this. In this case, you probably want to look at getting a new set of pads.
- Brake pads becoming worn down – As we mentioned earlier, brake pads are designed to produce a not-very-nice-sounding noise when they begin to get too thin. This would be described by most people as more of a “screech” than a “squeak,” though.
Causes of Squeaking in Drum Brakes
- Lack of lubrication – (Note: do not lubricate the shoe surfaces!) This will cause the brakes to fail completely, and you will crash. If you have any doubts at all about this, take your car to a mechanic. There are contact points on the inside of the shoes that may need lubrication. This lack of lubrication can lead to the shoes constantly touching against the drum, causing a squeaking sound as you drive. This noise will probably be constant, rather than solely when you are pressing the brake pedal. It will also only come from the wheels with drum brakes on them (if any, this will likely be one of the rear wheels).
- Brake service needed – If you have old brakes, it’s a good idea to get your drum brakes serviced. This is possible to do yourself, but it can be quite fiddly, especially to put everything back together. Servicing drum brakes essentially involves taking it all apart, using a wire brush to clean all the rust and residue off the shoes and the inside of the drum, and potentially replacing the spring with a new one. This will make sure your brakes are working as well as possible. It may also simply just be time for some new shoes (that’s for your drum brakes, not you).
So there we have it: several different causes that may be leading to a squeaking noise coming from your brakes.
If none of these seem to be the cause, we would recommend taking your car to a trusted mechanic who can run a full diagnosis for you.
Thanks for taking the time to read this article – we hope it’s been useful for you!
As a final warning, always be careful when working with brakes yourself – messing up could potentially be life-threatening.