Brake pads are an integral part of a disc brake system. They are positioned facing the rotor, and when the driver presses the pedal, the brake fluid transfers pressure directly to the brake pads, squeezing them against the rotor and preventing it from turning. Because the rotor is attached to the wheels, when it stops turning, the car slows down and stops.

Brake pads are made of different materials, depending on the manufacturer, but they are always made of a softer material than the rotors. This means that brake pads wear faster when there is repeated friction between the two surfaces. This friction generates a lot of heat, and eventually the rotors will have to be resurfaced or replaced, but the brake pads will fail first.

Not all brake pads are created equal, and their lifespan may be longer or shorter based on a variety of factors, such as the pad material, your driving habits, typical driving conditions, and maintenance procedures.

General guidelines for how often to replace brake pads cover a pretty wide range: 20,000 to 70,000 miles. To better understand when to replace your pads, be sure to check your owner's manual. From there, watch for signs of wear and tear. A squealing or vibrating sensation when your vehicle comes to a stop are clear signs that your brake pads are too low. Many pads have built-in "alarms" that squeal when the alarm drops below a certain level and should not be ignored.

Visual inspection is also critical. Pads should be replaced when they are less than 1/4 inch thick. Ignoring these signs and allowing the pads to wear down to the backing not only jeopardizes your safety, it can damage the rotors and result in a more expensive repair than simply replacing the pads.

There are a few factors that can cause your brake pads to wear out faster, and some of them are more under your control than others. Of course, the more you use them, the faster they wear out, so those who frequently drive in stop-and-go cities or in hilly areas that require frequent braking on downhill grades may need to replace their brake pads more frequently. Typically more common than those whose vehicles use mostly flat highway conditions.

Your habits are also important. You can protect your brake pads by avoiding hard braking, placing trash in the trunk to reduce vehicle weight, downshifting when going downhill, and driving at or below the speed limit. Low brake pads can cause rotors to warp, which can quickly cause the pads to wear out again—an annoying and potentially dangerous cycle—but sticking to regular maintenance can help you stay on top of the situation.

Most of the time, the brakes will tell you when the speed is getting lower, so pay attention to them. Inspect your brakes as part of routine maintenance, and always investigate any unusual noises or sensations related to your brakes.