GMC brakes are engineered to give you plenty of warning when the braking system has become worn-out or faulty. The brake pedal might be 'hard,' or resistant to pressure. Or, the brake might require a tremendous amount of pumping to react quickly. There might be vibrations or pulsing when you hit the brakes. You might hear squealing at low speeds that are emitted from your break wear sensors. You can check for brake pad wear by viewing the pads from outside the front tire. On most cars, you can look through the openings on the outside of the wheel/rim assembly to see the pads. If the pad depth is less than ? inch, then replace the GMC brake pad soon. If it's less than 1/8 inch, you are risking damage to the rotor and replace those pads with genuine GMC brake pads immediately. Take time to inspect your brakes and the individual components. The braking system is a complex set of components that in the end, can save your life in an accident. Your GMC brakes, if they are disc brakes, are made of brake calipers, brake pads, rotors and caliper mounting hardware. If you have GMC drum brakes, they consist of brake backing plates, brake drums, brake shoe self-adjusters, brake shoes, brake springs and wheel cylinders. Each component should be inspected, then replaced if there are signs of rust and wear and tear.