What Causes the Squeaking Noise When Starting and Braking?

[KyleAnn]

The causes of squeaking noise when starting and braking are: 1. Metal particles or small gravel between the brake pads and brake disc; 2. Excessive wear of the brake disc or brake drum; 3. Overly hard brake pads; 4. Rusty brake caliper; 5. Inflexible handbrake cable; 6. Slow return of the master brake cylinder. Solutions for brake squeaking include: 1. Checking the lubrication of the shock absorber top rubber or buffer rubber; 2. Breaking in new brake friction pads; 3. Replacing brake pads promptly; 4. Cleaning foreign objects from the surface of the brake disc. Braking, also known as deceleration, refers to the action of stopping or reducing the speed of moving locomotives, vehicles, other transport tools, or machinery.

[Ellie]

I've encountered this situation many times, especially on rainy days or after the car has been parked for several days. Usually, it's because the brake disc surface has some rust, and when you step on the brake to start, the rusted area rubs against the brake pads, making that squeaking sound. It should go away after driving for a while and the friction cleans it off. If there's a sharp metallic scraping sound every time you start, it might be that the brake pads have worn to their limit, and the warning metal piece is making contact with the brake disc as an alert signal. Another possibility is that there's a small stone or other foreign object stuck in the brake caliper. I would first check the thickness of the brake pads; if it's below 3mm, they need to be replaced, otherwise, it not only wears out the brake discs faster but also affects safety. If the brake pads have just been replaced, it might be that the new brake pads haven't fully broken in yet.

[OJudah]

This issue is quite common and usually nothing to worry about. I've experienced it a few times, all due to temporary causes: brake discs getting wet from rain and rusting, or brake pads picking up some dust, which disappears after some wear. If the noise persists for a long time, first recall whether you've recently driven through puddles or in the rain, as water may have entered the brake caliper and caused rust. Another easily overlooked situation is driving with the handbrake not fully released, causing continuous friction on the brake disc. For new cars, the brake pads might contain more metal components, making them harder and more prone to noise, but this should improve after a few thousand kilometers. However, if accompanied by a softer brake pedal or longer braking distance, immediately visit a repair shop to check for brake fluid leaks in the brake lines.

[McSarah]

I have summarized three common causes: first, rust on the brake system, especially on vehicles parked after humid weather; second, brake pad wear alerts, where the metal piece contacts the brake disc and produces a sharp sound; third, uneven brake discs with grooves, causing uneven friction and resulting in abnormal noises. The solution depends on the specific situation: temporary rust can be ignored, but if the wear reaches the warning line, the brake pads must be replaced. Deep grooves on the brake disc require resurfacing. As a reminder, don’t use low-quality brake pads to save trouble—they may break under high temperatures. If the noise occurs in a new car, it will likely resolve itself after a few hundred kilometers, so there’s no need for immediate action.