What Causes the Noise When Braking a Car?
4 Answers
There are several reasons for noise when braking a car: 1. If there is a slight squeaking sound at the pedal position when lightly pressing the brake while the vehicle is stationary, this is mostly caused by the return spring of the brake light switch on the brake pedal; 2. If there is a noticeable squeaking sound when braking at low speeds, the noise comes from the brake disc area. Many new cars or those that have recently had their brake pads replaced often experience such braking noise issues during driving. The steps to check the brakes are: 1. Inspect the brake pads. The effectiveness of braking largely depends on the condition of the brake pads, so checking whether the wear level of the brake pads is normal is crucial for ensuring braking performance; 2. Check the brake fluid. It is important to consider the weather characteristics of your location and destination to prevent excessive moisture from entering the brake fluid, which could adversely affect braking.
I get particularly nervous every time I encounter brake noise. Last time I went to the mechanic, they found that the brake pads were worn thin. It turns out that when the brake pads wear down to the warning indicator, the metal friction between the pads and rotors produces a high-pitched screech, which feels like nails on a chalkboard. Another common issue is rust on the brake discs, especially noticeable after rain, but it usually wears off after a few brake applications. Pebbles stuck in the calipers can also cause a clicking sound, and you might hear a crunching noise when reversing. Additionally, loose suspension components can lead to squeaking sounds during braking. It's best to check the brake pad thickness monthly with a flashlight—replace them if they're below 3mm. If you encounter continuous unusual noises in an emergency situation, be sure to increase your following distance!
With ten years of experience in car repair, brake noises can be categorized into several scenarios: a high-pitched squeal is likely due to worn-out brake pads, where the metal backing plate directly scrapes against the brake disc; a rustling sound indicates trapped debris like small stones or metal shavings; a rumbling noise might suggest a faulty brake caliper, often accompanied by steering wheel vibration when braking. Occasional noise in new cars is normal, but if it persists beyond 5,000 kilometers, an inspection is necessary. I recall a customer who delayed repairs for three months, resulting in deep grooves on the brake disc and doubling the cost to replace the entire brake system. Nowadays, after washing a car, I advise owners to pump the brakes a few times to remove water rust, which helps extend the brake disc's lifespan.
I've changed three sets of brake pads before realizing how particular the materials are. Metal pads are cheap but always squeak when the car is cold in winter. Semi-metallic pads are quieter but produce a lot of black dust. Ceramic pads are the quietest, though they cost twice as much and can still squeak in rainy weather. The last time I upgraded to slotted rotors, which solved the weird braking noise in the rain. Now, during every maintenance session, I make sure the mechanic measures the brake disc thickness—if it's below 22mm, it must be resurfaced. The maintenance manual states that the brake caliper grooves should be cleaned of sand particles every 20,000 kilometers, a job you can do yourself by removing the tires. If you hear a rubbery squeaking sound, it's usually due to hardened, aged dust boots.
