1. Squeaking or Squealing Noise: Many brake pads have built-in wear indicators that produce a high-pitched squeal when the pads are worn down. This noise serves as an early warning that it's time for a replacement.

2. Grinding Noise: If you hear a grinding noise when braking, it could mean that the brake pads are severely worn and the metal backing is making contact with the rotors. This situation requires immediate attention to prevent further damage.

3. Reduced Braking Performance: If you notice a decrease in braking performance, such as increased stopping distances or a soft brake pedal, it could be a sign that the brake pads are worn and need replacing.

4. Vibration: Pulsation or vibration in the brake pedal when applying the brakes can indicate uneven wear on the brake pads or warped rotors.

5. Warning Light: Some vehicles have a warning light on the dashboard that illuminates when brake pad wear reaches a critical level. Consult your owner’s manual for specific details about this feature.