To have brakes on a vehicle work effectively there needs to be friction. The brakes need to get rid of the kinetic energy. The brake pads put force on the brake rotor to cause friction.When you press your foot on the pedal it forces a rod to pushes a piston in master cylinder which pushes the brake fluid causing the brake pads to close.So if dirt gets on the brake pads or rotors it causes it not to get enough friction to stop the vehicle. My product clean that dirt off to make sure the brakes can work.