Why Does the Brake Squeak When Pressed?

[ClaraFitz]

The reasons for squeaking when pressing the brake include: 1. Issues with brake fluid—insufficient, deteriorated, air-contaminated, or long-unreplaced brake fluid can cause the problem; 2. Oil leakage at the brake cylinder or pipeline joints, resulting in an inexplicably increased brake pedal travel or the pedal not returning, leading to squeaking; 3. Air in the brake lines that needs to be bled; 4. Problems with the master brake cylinder; 5. For some models with rear drum brakes, excessive clearance between the brake shoes and the brake drum can also cause squeaking. Braking, also known as deceleration, refers to the action of stopping or reducing the speed of moving locomotives, vehicles, other transport tools, or machinery.

[Ophelia]

I usually drive to and from work, and I've encountered the situation where the brakes squeak several times. The sound is like a mouse screeching on the wheels, which is quite scary. It's mainly because the brake pads are worn too thin, and the metal components inside directly rub against the brake disc, producing a harsh noise, especially when slowing down to stop gradually. Another possible reason is excessive moisture from rain, causing the brake disc to rust. The squeaking may occur briefly when starting the car but then disappear, indicating rust particles sticking to the surface. Dust or small stones getting stuck in the brakes can also create noise and affect braking performance. I suggest that whenever you hear such sounds, don't delay—visit a repair shop to check the brake pad thickness. If they're too thin, replace them immediately. Safety comes first, or else the braking distance may increase, leading to accidents. I’ve learned this the hard way—I almost rear-ended someone once.

[McSimon]

From a safety perspective, squeaking brakes should never be ignored as it often signals urgent issues with the braking system. Common causes include brake pads worn down to expose high-hardness metal ribs that directly scrape against the brake discs, or uneven brake discs with grooves. More hidden problems could involve caliper malfunctions, such as rusted or stuck guide pins preventing complete brake pad retraction. Once these issues worsen, they may lead to reduced braking power, increasing accident risks during emergencies. Especially in urban traffic congestion with frequent braking, the persistent squeaking serves as a reminder for immediate inspection. I recommend scheduling a professional check-up as soon as continuous squeaking is heard to eliminate potential hazards and protect both personal and others' safety—don’t wait until the noise escalates to scraping or vibration.

[AmaraLynn]

The most common cause of squeaking is excessive brake pad wear. The thin pad contains a metal fiber layer that starts to scratch the brake disc once the outer layer is worn away. Additionally, dust or dirt trapped in the brake components, or improper adjustment of the assembly gap causing misaligned brake pads to repeatedly rub against the edges, can also lead to noise. Temporary squeaking may occur if the brake disc surface rusts after the car is exposed to rain. For a quick fix, check around the tires for obvious foreign objects, but deeper issues require removing the wheel to inspect whether the brake disc is smooth and even or if the brake pad thickness is below 3mm, in which case replacement is necessary. Regular maintenance can help avoid these troubles.

[LaGia]

Especially during rainy and humid seasons, stepping on the brakes can easily cause squeaking. When the air humidity is high, metal components like the brake disc surface absorb moisture and develop a thin layer of rust, resulting in short friction noises when starting to drive. These noises usually go away after driving for a while. However, if the car is frequently parked outdoors, the noise can become more persistent and may even be accompanied by vibrations. Dust accumulation or salt corrosion near coastal areas can also be contributing factors, roughening the contact surfaces between the brake pads and discs. The solution is to drive out after rain and apply the brakes several times to remove the rust. In the long term, keeping the garage dry and minimizing exposure is key. I've seen a friend ignore this issue, leading to warped brake discs that required expensive replacements—definitely not worth it.