What Causes Abnormal Noise When Braking Just After Starting the Car?

[DeDiana]

The reasons for abnormal noise when braking just after starting the car are: 1. When the brake discs rub, they produce some metal dust, which can cause abnormal noises when braking. This type of noise from the brake pads is a normal phenomenon; 2. Abnormal noise from the brakes indicates that the brake pads have reached their wear limit, causing friction between the brake warning shim and the brake disc, resulting in a metal-on-metal sound. Solutions for abnormal noise when braking just after starting the car: 1. Firmly press the brakes several times or perform emergency braking in an open area, and the situation will improve; 2. It is necessary to replace the car's brake pads in time to prevent any potential hazards.

[VanAlex]

In winter mornings, my car always makes a 'squeaking' sound when I step on the brakes after starting it. I later specifically looked into it. Most of the time, it's because the brake discs and pads get damp and rust overnight, or the brake pads are too cold, causing the friction coefficient to be unstable when first applied. This is especially noticeable if the car was parked outside in the rain—it usually goes away after driving for a few minutes as the rust wears off. However, if the noise persists after driving for half an hour, it's necessary to check whether the brake pads have worn down to the limit indicator or if the brake discs have developed deep grooves. During the last maintenance, the mechanic measured with calipers and said the brake pads need replacement once they're down to 5mm, otherwise, it could damage the discs and cost more.

[LaBrooklyn]

Based on my years of car ownership experience, the most common causes of cold brake noise are three: first, the physical properties of the hard particles in metal brake pads and the brake disc change when rubbing at low temperatures; second, surface rust forms on the brake disc after rain or car washing in the past few days; third, issues with the material composition of the brake pads, as some semi-metallic pads harden at low temperatures. Once, when I had noise and went for inspection, I found that the caliper guide pins were slightly stuck, preventing the brake pads from fully retracting. Remember, if there's a sharp metal scraping sound that persists, you must immediately check the brake pad thickness to prevent wearing through and damaging the caliper.

[MacDiana]

Don't worry too much about brake squealing when starting up, it's mostly caused by humidity or temperature. My car improved a lot after switching to ceramic formula brake pads, whereas the semi-metallic ones would always squeak in the morning. However, pay attention to these special situations: new brake pads require a 200-kilometer break-in period; stepped wear on the edge of the brake disc; or continuous friction between pad and disc due to poor caliper retraction. Last time, my neighbor's car was squeaking, and it turned out to be a small stone stuck in the wheel hub.