What Causes Metal Friction Noise Without Braking?
3 Answers
There are four main reasons for metal friction noise when not braking. Excessive Brake Pad Wear: When the brake pads are too thin, the metal is exposed, causing the sensor on the brake pads to be worn off and trigger an alarm. Additionally, the friction between the metal part of the brake pad and the brake disc will produce noise. In this case, it is recommended to replace the brake pads and check if the brake disc thickness meets the requirements. Gravel Between the Brake Disc and Brake Pad: This situation usually occurs after the vehicle has driven through water, where mud and sand are carried into the gaps. When the brake pads and brake disc rub against each other, the temperature can reach 800-1200 degrees Celsius, making the brake pads very soft. Naturally, small stones can easily embed into the brake pads, producing a sharp friction noise. Brake Drag: If the brake piston fails to return to its normal position after braking, the brake pads remain in a braking state, which can also cause abnormal noises during high-speed driving. Abnormal Wear of the Brake Disc or Brake Pads: If the brake disc is deformed, damaged, dented, or raised due to external forces, or if the brake pads wear unevenly, causing an uneven surface, friction noise can occur even when braking.
I can relate to this issue deeply as I encountered a similar situation while driving last time. When the car was moving at low speeds or turning, there was a noticeable metal grinding noise, especially noticeable when going over speed bumps. After taking it to the repair shop, it turned out that the brake pads were worn too thin, and the warning metal piece was directly rubbing against the brake disc, causing the noise. It could also be due to small stones getting stuck in the brake disc or loose ball joints in the suspension system on bumpy roads. The most troublesome scenario is a damaged wheel hub bearing, where the grinding noise gets louder as the speed increases. In such cases, it's really not advisable to delay repairs. I waited two weeks before fixing it last time and ended up spending several hundred more to replace the brake disc. It's recommended to have it checked by a professional as soon as possible, especially paying attention to the thickness of the brake pads. Timely replacement can save a lot of money.
I often help friends deal with car noise issues. If you hear a metal grinding sound without pressing the brake, it's most likely a problem with the braking system. The most common cause is worn-out brake pads, where the metal backing plate starts grinding directly against the brake disc. It could also be due to a warped brake disc or a bent dust shield touching rotating components. Additionally, check the wheel bearings, as they produce a continuous humming or grinding sound when damaged. Worn suspension bushings or steering linkage ball joints can also cause noises. Don't forget to inspect the chassis components—sometimes a broken exhaust pipe hanger can create a metal grinding sound. If the noise changes with vehicle speed, it's likely a rotating component issue; if it only occurs on bumpy roads, it's more likely a suspension problem. It's best to get it checked as soon as possible to prevent minor issues from turning into major faults.
