Grinding, Squealing, & Pulsating Are All Bad
The Friction That Helps You Stop Your Vehicle Comes From Hydraulic Pressure Forcing Your Brake Pads Against Your Rotors And Squeezing Them Until They Stop. Given Enough Time, Every Brake Pad Will Wear Itself Down To Nothing.
Take action at the first sign of trouble. Squealing and Squeaking are usually the first indicators. Their are actually tabs built into the pad itself and their entire purpose is to make noise when your brake pads are too low.