Brakes are a very important part of vehicle safety. Insufficient braking due to lack of maintenance can lead to trouble. As soon as you suspect that the performance of the brake system is suspect or not performing properly take it to a Certified Shop for a brake inspection.
Brake wear is something that needs to be checked visually. There are some indications as the driver that you can look for. Some pads have a wear indicator on them that will make a squealing sound or illuminate a light on the dash. If the rotors go bad they will cause a slight vibration when the brakes are applied. If the brake fluid is low this indicates either brake wear or a fluid leak. The front brakes are approximately 75% of the braking force. Vehicles are equipped with a height sensing valve that increases the rear braking force to the rear wheels when the weight distribution is heaver in the rear.
Several components may need to replace when doing a brake replacement. A certified technician will determine the defective components by removing and inspecting them for serviceability. The brake pads and rotors are the two components that slow the rotation of the tire and wheel. The friction on the pads and rotor cause wear which leads to the replacement of these components. The brake caliper and hardware are subject to rust, corrosion and hydraulic leaks. For the most part these components will not need replaced as often as the pads and rotors.