What symptom might indicate that a brake pad is worn out?

A brake pad that is worn out often produces a distinct sound when in use, commonly described as squealing. This noise typically arises from a built-in wear indicator that becomes exposed as the brake pad material diminishes. The purpose of this indicator is to alert the driver that the brake pads require replacement due to insufficient material to function effectively.

While increased braking distance can be an indication of brake pad wear, it is not as immediate or noticeable as the auditory cue provided by the squealing noise. Likewise, a quiet braking sound might suggest that the brakes are functioning well, and no change in brake pedal behavior would imply that there are no issues. Therefore, the presence of squealing noises serves as a direct and audible signal to the driver about the state of the brake pads, making it a strong indicator of wear.