Why Are My Brakes Squeaking? Causes and When to Worry

The short answer

Brakes that squeak for the first few stops of the day are usually fine. Overnight moisture leaves a thin layer of surface rust on the discs, and the pads wipe it off within a few applications. A squeal that happens every time you brake, however, can mean your pads are worn down to their built-in wear indicator, or that the pads are glazed, contaminated or vibrating against the caliper.

Squeaking is a very different sound from grinding. A high-pitched squeak or squeal is often an early warning. A harsh metal-on-metal grinding usually means the pads are already worn out, which we cover in our separate post on grinding brakes. If you hear grinding, book the car in straight away.

Harmless squeaks

Surface rust is the most common. It is worse after rain, a car wash or a frosty night, and disappears after a few gentle stops. Cars that sit unused for a week or more can build up more rust and may squeak for a little longer.

Brand new pads and discs can also squeak for the first hundred miles or so while they bed in against each other. Dust and small bits of grit caught between the pad and disc can cause a squeak too, and usually clear themselves.

Squeaks that are a warning

Many brake pads have a small metal tab called a wear indicator. When the pad material gets thin, the tab touches the disc and makes a steady squeal, often while you are driving and not just when you press the brake. It is designed to be annoying so you notice it. Some cars use an electronic wear sensor and a dashboard warning light instead.

Glazed pads are another cause. Hard braking, or dragging the brakes down long hills, can overheat the pads so their surface goes hard and shiny. They squeal and may not grip as well as they should.

Pads contaminated with oil, grease or brake fluid can squeal and lose grip too. That points to a leak nearby, such as a caliper seal or a hub seal, which needs finding and fixing, not just new pads.

Vibration: the hidden cause

Most brake squeal is simply vibration. The pad vibrates against the disc at a high frequency and you hear it as a squeak. Pads are normally fitted with shims and backing plates, and the contact points are lightly greased with the right brake grease, to stop that vibration.

If those shims are missing, the sliders are dry or sticking, or the pads are poor quality, squealing is common even when everything is otherwise in good condition. Correct fitting and decent parts solve most of these cases.

Rust can also build up on the outer edge of the disc, where the pad does not reach. Over time that lip of rust can catch the edge of the pad and cause a squeak or a scraping noise, particularly on cars that do low mileage or short trips.

Other signs to watch for

A squeak on its own is rarely an emergency. Get the brakes checked promptly if the squeak comes with any of these: the car pulls to one side when braking, the pedal feels soft or goes down further than usual, you feel a vibration through the pedal or steering wheel, a brake warning light comes on, or one wheel is much hotter or dirtier with brake dust than the others.

Any of those can point to a sticking caliper, a warped disc or a hydraulic problem, which affect how well the car stops.

Also listen to when the noise happens. A squeak only when braking points to the pads and discs. A squeak or chirp while driving that stops when you brake is often the wear indicator. A noise that continues whether you brake or not, and changes with speed, may not be the brakes at all, and could be a wheel bearing or something caught near the disc.

Try not to fix a squeak yourself by spraying anything onto the discs or pads. Lubricants and cleaners that are not made for brakes can contaminate the pads and make stopping worse.

Getting squeaky brakes checked

The only way to know whether a squeak is harmless is to look. At MF Autocentre in Walsall we take the wheels off, measure the pads and discs, check the calipers and sliders move freely, and look for leaks or contamination. If the brakes are fine, we will tell you. If something needs doing, you get a clear quote first.

Call us on 01922 636820 or book online if your brakes have started squeaking and you would like peace of mind.