Buying automotive parts can be intimidating, so it's important to "research and quote" before you buy. Most F150s have drum brakes on the rear axle and disc brakes on the front. Drum brakes use "shoes" inside of a rotating drum to create friction that produces braking force. Disc brakes, on the other hand, work like bicycle brakes. There is a rotating disc that two brake pads push on from either side to produce a braking force. Since an F150 has both disc and drum brakes, the prices for the brakes depend on what you are replacing.
Visit the websites of auto parts stores such as Autozone.com or OReillyAuto.com, and compare the prices if you know the parts you need.
Call local automotive repair shops and parts stores and ask for quotes on the parts you need.
Check with an automotive repair shop if you do not know which parts you need. (These could be pads, rotors, brake fluid, etc.) Ask whether the shop will charge for the inspection of your brakes. If they don't charge, then you are set. After the inspection, the mechanic will tell you what needs to be done and quote you on the repair. Now you have the option of repeating steps 1 and 2 to find the lowest price for brakes.
