We've all been through it: you're approaching a light when the vehicle next to you gives off a high pitch squeal as they come to a stop. The driver, red with embarrassment looks away as you stare and think to yourself - "What's wrong with your car??!!!"
Well, that high pitch squealing noise is letting the driver know it's time to change their brakes!
Most vehicles today are equipped with disc brakes (at least in the front) with the main components being a caliper, rotor and a brake pad. The brake pad receives the most wear and tear. Why? A moving vehicle has a certain amount of kinetic energy. When you apply your brake pedal, the idea is to remove the kinetic energy in order to stop. Your brakes do this by converting the kinetic energy to heat, generated from squeezing the brake pads on the disc. So, as you can imagine, constant friction between the brake pads and the disc cause the brake pads to wear out.