What Causes the Friction Noise from Hard Spots on Brake Pads?
3 Answers
Introduction to the causes of friction noise from hard spots on brake pads: 1. Stiffness between the brake disc and brake pads: This can be resolved by adjusting at a repair shop. The noise may also be related to hard spots on the brake pads, primarily caused by excessively hard friction material in the pads. Sanding the brake pads with coarse sandpaper can help. 2. Inspect the brake disc: Foreign objects between the disc and pads, or grooves on the disc causing localized friction, can also lead to noise, though such brake noises are usually intermittent. 3. Severe wear on brake pads or discs: These should be replaced promptly to avoid serious consequences. Brake pads should generally be replaced when their thickness falls below 2mm. 4. Activation of the ABS anti-lock braking system: During rainy or snowy weather, when braking over speed bumps, or during emergency braking, a rhythmic "clicking" sound similar to gunfire may occur, accompanied by strong vibrations in the brake pedal. This indicates the vehicle's ABS system is activated, causing the brake noise. There's no need for concern in this situation; normal driving can continue.
I've been repairing cars for over a decade and have seen many cases of brake squealing caused by hard spots in brake pads. Simply put, hard spots are small hard particles embedded in the friction material of brake pads, such as metal shavings, impurities, or unevenly mixed raw material chunks. When you apply the brakes, these hard particles rub against the brake disc, producing a sharp squealing noise, much like metal scraping against glass. The causes? Uneven material mixing during manufacturing can easily create hard spots; during use, sand, rust, or debris getting into the brake pads can also embed and form hard spots. More seriously, repeated high temperatures can harden the material and exacerbate the problem. This noise isn't just annoying—it also wears down the brake discs, shortening their lifespan. I recommend car owners regularly inspect their brake pads, choose reputable brands, and avoid hard braking in sandy areas—addressing issues early saves both hassle and money.
Having driven for decades, I'm quite familiar with this harsh scraping sound. Noise caused by hard spots usually stems from rigid particles embedded in brake pads, creating uneven pressure during friction. Common causes include aged/deteriorated brake pads, accumulated dust, or metal shavings adhering to rusted brake rotors. Long-term neglect can score the rotor surface, leading to louder noises or even brake failure. From my personal experience – inspect immediately upon hearing the sound, don't wait for major issues. Lightly sanding the pads may occasionally help, but replacing them is often the only permanent solution.
