What Causes the Squeaking Sound from Brake Discs When Starting a Cold Car?

[DiHannah]

The reasons for the squeaking sound from brake discs when starting a cold car are: 1. Use of inferior or overly hard brake pads; 2. Presence of sand or foreign objects between the brake pads and brake discs; 3. Severe wear of the brake discs; 4. The brake pads have worn down to the warning line. A brake disc is a circular disc that rotates as the vehicle moves. When the brakes are applied, the brake calipers clamp onto the brake disc to slow down or stop the vehicle. The brake disc is a crucial component in the braking system, which can be categorized into disc brakes, drum brakes, and air brakes based on type. Structurally, they are divided into solid brake discs and ventilated discs, and by material, they include carbon fiber ceramic brake discs and metal brake discs.

[ElizabethFitz]

The common cause of squeaking brake discs during cold starts is the noise generated by moisture or dust adsorbed on the brake discs while parked, which creates friction during initial movement, similar to the sound of scraping a rusty surface. I have personally encountered this situation multiple times, especially after parking in rainy seasons or humid environments. A few squeaks at startup that then disappear are generally not a big issue. However, for peace of mind, I simply check the condition of the brake pads to ensure there is no significant buildup of dirt or rust. Another factor is material contraction due to temperature changes, which can amplify the friction noise. It's advisable to park in a dry location and lightly press the brakes a few times before starting to clean the surface. If the noise persists or there is a sensation of brake shudder, it's time to visit a repair shop to check the flatness of the brake discs and the wear of the brake pads, to avoid long-term neglect affecting braking safety. This is usually a minor issue, but I always remind myself not to take it lightly.

[StJeremiah]

I often explore mechanical principles through car tinkering and have found that the squeaking noise from brake discs during cold starts usually stems from friction caused by surface oxides or tiny impurities. When the metal is cold upon startup, rust spots or dust on the brake discs can produce a squeaking sound under pressure, especially more frequently on humid days. In practice, I've tried gradually accelerating and lightly tapping the brakes, which often alleviates the noise. This issue may also relate to brake pad materials—some containing metal components tend to accumulate hard spots that generate noise. Another factor is clearance changes: thermal contraction causes looser contact between brake components, leading to momentary friction-induced vibrations and noise during startup. I recommend DIY periodic cleaning of the brake area using a soft brush to remove debris. If the noise persists, checking brake disc thickness or switching to high-quality brake pads can significantly improve driving comfort and reduce potential failure risks.

[BriannaAnn]

I encounter the issue of brake noise during cold starts several times during my daily commute, mostly caused by moisture or dirt on the brake disc surface. A simple test is to lightly press the brakes a few times after starting to see if the noise disappears; if it doesn't make noise, it's usually not a big deal. Possible causes include water residue after car washing, especially when parked overnight leading to natural rust formation. Personally, I pay extra attention to brake performance, and if the noise is loud, I quickly check at a roadside shop. Money-saving tip: Choose dry parking spots and avoid muddy roads.