What Causes the Thud Sound When Starting and Braking a Car?

[OmarDella]

Reasons for the thud sound when starting and braking a car: 1. If the thud occurs during emergency braking, it may be due to the activation of the ABS anti-lock braking system; 2. If the thud occurs during low-speed braking, it may be caused by issues with the brake pads or brake discs, such as incorrectly installed brake pads, mismatched models, or foreign objects on the brake pads or discs; 3. If the thud occurs when starting, it is likely due to foreign objects in the tire treads; 4. There may be a fault in the car's suspension system; 5. If the abnormal sound occurs during sudden starts and there is no noise when the engine is idling, the issue is likely with the carbon brushes inside the starter motor.

[CassandraAnn]

A clunking sound when braking at car startup is actually quite common. My car used to do the same, and it's usually an issue with the brake pads. If the brake pads are worn too thin or have debris stuck in them, they can make a clunking noise from friction during initial movement. Sometimes, it's due to loose ball joints or bushings in the suspension system, causing chassis vibration when braking. Or, with new cars during the break-in period, components may not have settled properly, leading to temporary noises. I typically start by checking if all the wheel bolts are tightened and inspecting the brake disc surface for rust or scratches. If the noise persists or the brakes feel less responsive during startup, I take it straight to the repair shop—they can use professional tools to test brake fluid pressure or caliper condition. Never ignore it; brake safety is critical, as failure mid-drive could be extremely dangerous. For regular maintenance, I periodically clean dirt around the wheels to minimize such noises.

[MacJesse]

Hearing the clunking sound when starting and braking makes me quite uneasy. Once on a rainy day, it sounded like metal hitting metal. It could be due to severely worn brake pads with increased gaps, causing instability when the pads and discs engage during startup. Alternatively, the suspension brackets might be loose, causing shaking when the car moves. Some new cars might also produce clunking sounds during the first few thousand kilometers as parts break in. I think it's best to first check for any abnormal wear marks on the brake discs, such as grooves or rust spots. Also, inspect around the tires for any stuck stones and try shaking the wheels by hand to check for looseness. If the issue persists, take it to a reliable repair shop where they can test the relays or hydraulic system. For safety, avoid disassembling things yourself—I once saw a neighbor's car nearly crash due to brake failure from this issue. Always pay attention to maintenance schedules and don't wait until the noise gets worse to address it.

[PatrickLee]

From a car repair experience perspective, the clunking sound during starting and braking is mostly caused by loose brake pads or poor retraction of the caliper pistons. It could also be due to aging suspension ball joints or stabilizer bar bushings, which produce abnormal noises upon acceleration. During inspection, first open the hood to check if the brake fluid level is normal. Low fluid levels can increase the risk of noise. I recommend parking the car securely and then tapping around the wheel area by hand to listen for echoes and locate any loose points. If the issue occurs frequently, it indicates a system problem that should be repaired immediately. Don't ignore changes in sound, as prolonged neglect can lead to accidents. Regular replacement of brake pads can prevent this.

[DiJustin]

I often encounter a clunking sound when starting or braking in my family car, especially in cold weather. There are quite a few possible causes, such as worn brake pads or debris causing friction issues during startup. It could also be loose suspension fasteners causing vibrations. My habit is to bend down and check under the wheels after parking - if there's no debris, I simply check if the screws are tight. If the noise is severe, don't force it - find an open area to test brake responsiveness. Safety first, especially when driving with kids - never ignore even small sounds. Regular brake system maintenance every six months can help reduce noise. If the sound persists, have a technician check the chassis or brake hydraulics.

[LaAlessandra]

I'm a new driver and got quite nervous when I heard a clunking sound during starting and braking last time. My experienced driver friend said it might be due to unbedded brake pads or installation issues causing uneven tightness. It could also be normal noise from new components just starting to work. I tried driving a few times myself to observe the sound changes - if it disappears after smooth starts, it's probably fine. But if it occurs frequently, it needs checking, like inspecting whether the brake discs are even and free from water accumulation or rust. I suggest checking the owner's manual for tips or searching online for similar cases, so as not to delay repairs due to minor issues.