A disc break works by the property of friction when a set of pads press against a rotating disk / disc. The pads are known as break pads, typically in a set of two, one of each side of the disc. The disc is connected to the axle. To stop the wheel, friction material in the form of brake pads, mounted on a device called a brake caliper, is forced against both sides of the disc. Friction causes the disc and attached wheel to slow or stop. Brakes convert motion to heat, and if the brakes get too hot, they become less effective, a phenomenon known as brake fade.
mechanical assembly
Unloaded, Loaded, Semi-loaded Calipers
The difference between "loaded" and "unloaded" calipers is simply what is included with the caliper. Most parts stores offer a "loaded" caliper, which includes the brake pads, clips/pins, and other necessary hardware needed to do a brake job on your own. An Unloaded caliper is just the caliper and the piston - no pads or other hardware included. You'll pay less for an unloaded caliper, but if you are doing a brake job and need everything, the loaded unit provides just about everything you'll need.
- Unloaded - Caliper
- Loaded - Caliper, caliper mounting bracket, hardware (shims, sometimes bolts, rubber thingies, metal retainer thing), pads
- Semi-Loaded - Caliper, caliper mounting bracket, hardware, no pads.
Many professional mechanics recommended using unloaded and buying the components individually. Loaded break assembly kits typically include the lowest quality break pads.
troubleshooting and repair
stuck brake caliper
You are stranded on the highway and your break caliper is stuck, the disc is so hot the metal has tinted blue and it is smoking. Do NOT spray WD-40 on it you idiot! WD40 is basically a mix of oil and gasoline, stuff you don't want to introduce to hot metal. In a pinch, silicone spray lubricant is a better choice, but you need to stop and wait for it to cool down, up to a full hour. Then if you must you can spray it with silicone. You need to get that caliper to loosen up, so you can get yourself to a safe place. Use the e-brake to and be light on the brake pedal so you can get your vehicle to safety.
If you spray WD40 on the hot disc and caliper you risk starting a fire. Using WD40, silicone spray, or another liquid on the hot parts you risk warping the rotor and cracking the caliper from sudden cooling.