What Causes the Sharp and Piercing Sound When Braking?

[ElleAnn]

Car brakes producing a sharp and piercing sound can be attributed to the following reasons: 1. The brake pads have worn down to the metal backing, causing the metal to rub and produce noise, signaling the owner to replace the brake pads; 2. Small stones or debris have become lodged in the brake pads, a common occurrence during rainy weather; 3. Issues with the brake pad material, often resulting in noise when the car is cold. Brakes are mechanical devices designed to slow down or stop a vehicle, also known as decelerators. The car's brake pedal is located below the steering wheel. Pressing the brake pedal activates the brake linkage, which applies pressure to the brake pads on the brake drum, clamping the brake rotor and causing the car to slow down or stop. The manual brake (handbrake) is located next to the gear shift and is connected to the brake lever.

[VanAutumn]

That sharp screeching noise when braking is really annoying, and I just dealt with this issue myself. The most common cause is the brake pads wearing down to their limit, where the metal backing plate starts rubbing directly against the brake rotor, creating that metal-on-metal scraping sound. Another possibility is that newly replaced brake pads need a break-in period, and some noise during the first few hundred kilometers is normal. Small stones or other debris stuck in the wheels can also cause a clunking sound while driving. In cold and damp weather, a layer of rust on the brake rotor surface might lead to squealing during the first few brake applications. It's best not to delay—last time I put it off, the brake rotor got gouged, costing me hundreds more to replace. The most reliable way is to visit a repair shop and measure the brake pad thickness with calipers; if it's below 5 mm, it's time for a replacement.

[MadisonLee]

Last week, my car also had squeaky brakes. After inspection, they found a fine scratch on the outer edge of the brake disc. The mechanic said it was caused by metal particles in the brake pads. He showed me the caliper, and there were indeed shiny little hard spots inside. These hard particles not only scratch the disc but also reduce braking effectiveness. The fix is simple: either sand the brake pads with sandpaper or replace them with ceramic ones. By the way, if there's a brief squeak when starting in the rain, don't worry too much—it's usually just moisture on the brake discs drying off. But if the noise persists for half a month, especially getting louder during hard braking, then you must check the remaining thickness of the brake pads.

[StNora]

Brake squealing is not something to be taken lightly. My colleague ignored this sound and ended up with significantly longer braking distances on the highway. There are a few common causes: the brake pads are worn thin and the warning shim is squealing; the brake disc is scratched by foreign objects; or the brake pad material is too hard. I once encountered a special case—the edge of the brake disc developed a flange, which also caused squealing when rubbing. If the noise persists for three consecutive days, even when lightly applying the brakes, it's advisable to get it checked immediately. A mechanic once taught me a simple self-inspection method: feel the wheel hub temperature when parked (if it's hot to the touch, it indicates brake pad sticking), or check the brake disc under light for any blue overheating marks.