Why Does the Brake Make a Thumping Sound When Pressed?

[CadenRose]

Reasons for the thumping sound when pressing the brake include: 1. Rust on the brake disc or brake pads; 2. The car has just had new brake pads installed; 3. Excessive wear on the brake disc and brake pads; 4. Assembly issues, such as incorrect brake pad models. Solutions for the thumping sound when pressing the brake are: 1. Apply butter or specialized lubricant to the connection between the brake pads and brake caliper; 2. Regularly inspect and replace the brake disc and brake pads; 3. Reinstall the brake pads. Braking, also known as deceleration, refers to the action of stopping or reducing the speed of a moving motor vehicle or other transportation machinery. It is divided into drum brakes and disc brakes.

[RyleeAnn]

Last time I encountered a thumping noise when braking, it happened right after I got new brake discs installed. The mechanic spent quite some time inspecting with a flashlight and said the main issue was warped brake discs—when braking, they wobbled side to side like beating a drum. Another possibility was a stone stuck in the brake pads, causing a terrifying clunk when pressed. He used a measuring tool to check the thickness variation of the brake discs, and sure enough, they were unevenly worn. He also reminded me that if the lower control arm bushings were cracked, it could cause wheel displacement and produce strange noises when braking. He recommended lifting the car on a hoist to shake the wheels and inspect the undercarriage with a flashlight, as that’s more critical. The worst-case scenario would be loose suspension components, making a drum-like thumping noise over bumps.

[RileyAnn]

In my twenty years of driving experience, brake noises are mostly caused by aging chassis components. Especially after driving through puddles on rainy days, a water film forms on the brake pad surface, resulting in a hollow 'thud' sound when braking. Once, on my way home late at night, I heard a metallic clanking sound when braking. The next day, I found out the brake caliper guide pins lacked lubricant, causing the brake pads to rattle loosely inside the caliper frame. The guy at the tuning shop also mentioned checking if the dust boots were torn, and he'd even seen cases where screws got stuck in the wheel rim. Worn-out brake disc cooling grooves can lead to brake drag, producing a buzzing sound like a subwoofer vibration.

[ElizaAnn]

Last time when helping my neighbor troubleshoot the abnormal noise from his old Mercedes, I found the sound mainly came from the rear wheels. Upon disassembly, deep grooves were found worn on the inner side of the brake drum, causing the brake shoes to knock and produce clunking sounds. During testing, pulling the handbrake while lightly pressing the accelerator made the car body shake like dancing. Measuring the brake disc thickness revealed a 0.15mm difference, exceeding the standard, and it was more noticeable when the car was hot. I recommended checking if the dust boot of the wheel cylinder is leaking oil, as piston sticking can cause dragging brakes and resonance. Improper installation of aftermarket replacement parts is also problematic—I've personally seen cases where fixing bolts were forgotten to be tightened.