One of the most common complaints involving car brakes are unusual noises – namely a squeaking noise. Brakes are arguably the most important safety feature in any moving vehicle. Nobody is comfortable driving a car with faulty brakes, it is therefore important to keep braking systems in optimum condition.
Whilst some brake noise may be harmless, others are not and it can be difficult to differentiate between the types of noises. Any persistent and unusual noise may be a warning of a more severe problem and should be investigated at your local garage to ensure there is nothing wrong with your car.
How Do Car Brakes Work?
The car brake pedal is connected to a master cylinder inside the engine compartment. When the driver pushes down on the brake pedal, pressurised brake fluid from the master cylinder is forced along a network of brake pipes until it reaches the piston in each wheel’s hub. The hydraulically activated pistons force the friction material, be it brake pads or shoes, onto the rotating parts, causing the car to slow down and stop.
Most modern vehicles are fitted with a disc brake system. This is comprised of a brake disc, a brake calliper and brake pads. The car’s wheels are attached to rotors (metal discs) which spin alongside the wheels. When the brake pedal is pressed, hydraulic pressure forces the calliper piston to clamp the disc brake rotor between the disc and the brake pads creating friction – causing the car to slow down or stop.
These are a more common sight in older vehicles, resembling a drum in shape and are usually made from cast iron. The system consists of a hydraulic wheel cylinder, brake shoes and a brake drum. When the brake pedal is pressed, the hydraulic wheel cylinder is pushed against the inner surface of the rotating brake drum resulting in friction which forces the vehicle to slow down.
What Causes Squeaky Car Brakes?
Thinning Brake Pads
One of the most common causes of squeaking brake pads – consistent use means all brake pads eventually wear down and become thinner. As a safety precaution, many manufacturers fit a small steel strip to the brake pad. This scrapes on the disc as the pad wears away and reaches its limit – serving as an indication that the pads need changing. It’s worth noting however that different manufactures attach wear indicators in varying ways.
High Metal Content
Cheap brake pads with high metal content may also make a squeaking noise. All brake pads contain a percentage of metal, usually in the form of small particles – high quality brake pads contain more organic brake material. However, some cheaper brake pads may be made with a higher metal content, containing large chunks of metal, the large pieces of metal can scrape against the rotor causing a high-pitched squeak.
Sometimes overnight rain or condensation may cause a thin layer of rust to form on the rotor surface. When the rotor turns, the pads scrape the rust off causing a squeaky noise.
Other causes may include misaligned or loose callipers, warped rotors, loose wheel bearings, incorrectly sized pads or sticky pistons. Excessive vibration from the brake pad vibrating against the rotor can cause it to make a high squeaking noise.
Although most modern vehicles are fitted with front disc brakes, many vehicles still use drum brake systems in the rear. Squeaking drum brakes are usually a sign that the shoe to baking plate contact points need to be lubricated. Lack of lubrication can cause the metal to rust resulting in a squeaking noise with the rotation of the wheels.
Car Brakes Grinding?
The unmistakable ominous sound of grinding car brakes, rather like hitting a rumble strip at high speed, is a clear indication of a serious problem and a sign to stop driving the car immediately. Grinding noises are usually caused by a lack of brake pad material. The pads will have been completely worn away and part of the calliper is coming into contact with the rotors, the metal rubbing on metal causes the grinding sound.
Another cause of brake grinding may be a foreign object lodged somewhere in the calliper. In either case, the issue should be dealt with immediately.
Regardless of what is causing your brakes to squeak or make any other type of noise, they should be inspected and repaired as soon as possible. Newer vehicles will advise drivers when brake pads are reaching their wear limit with a dashboard warning, older models however will not. The importance of maintaining your braking system should not be under estimated. Regular servicing of your vehicle will ensure your brake pads are road safe and help you avoid expensive repairs caused as a consequence of worn brake pads.