There are several signs that indicate the need for brake pad replacement. These include squeaking or squealing noises when applying the brakes, grinding or scraping noises, reduced braking performance, longer stopping distances, a pulsating brake pedal, or a warning light illuminated on the dashboard. Additionally, visually inspecting the brake pads through the wheel spokes can provide an indication of their condition. If the brake pads appear excessively worn, uneven, or less than the recommended thickness, it is time for replacement.