Why does my car make a grinding noise when braking?

Quick answer

A grinding noise when braking almost always means the brake pads are worn down to the metal backing plate, which is now scraping directly against the rotor. Continuing to drive in this condition damages the rotors and dangerously increases your stopping distance.

Common causes

• Brake pads worn past the wear indicator down to the metal backing plate
• A small stone or road debris caught between the pad and the rotor
• Rust buildup on the rotor surface after the vehicle sat unused, especially in humid weather
• Worn or missing brake hardware (clips and shims) letting the pad drag on the rotor

How to diagnose it

1. Inspect brake pad thickness

   Remove the wheel and measure the friction material. Pads below 3 mm (1/8 inch) are overdue for replacement and likely the source of the grinding.

2. Check the rotor surface

   Look for deep grooves or a raised outer lip on the rotor. Light scoring can be machined smooth, but deep grooves mean the rotor must be replaced.

3. Clear any trapped debris

   Inspect the gap between the pad and rotor for trapped gravel or a small stone and remove it. A lodged pebble can mimic worn-pad grinding.

When to see a mechanic

• The brake pedal vibrates or pulses under braking
• The grinding continues after new pads are installed
• You notice brake fluid leaking near the wheel or caliper

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