Disc Breaks

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, typically all parts are individual. This is the most common situation.
• 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. WD-40 doesn't belong anywhere near any braking components at any time for any reason.

IMPORTANT: Remove cap from brake fluid reservoir to relieve pressure on caliper. If you don't do this you won't be able to separate the compressed caliper, especially if it is stuck!

preventing a stuck brake caliper

One way to keep your brake calipers from sticking is to give them a good spray with brake cleaner. There are times when road dirt, brake dust, and other particles will get into the calipers causing them to "gum" up and stick. Brake cleaner will help penetrate into the calipers and loosen them up.

• caliper slides: those two pins that screw ends that hold the caliper on your disc. They can get gummed up and stick, preventing fee caliper movement. Never use petrolium based grease on these caliper slides. Use silicone based caliper slide grease.
• caliper piston: if the caliper slides aren't causing the caliper to stick, then it is probably the piston. It is the part in the center that pushes the pad when break fluid pressure builds against it.
• note that other factors besides caliper slides and piston can cause a caliper to stick, such as a pinched or collapsed break line.

remove caliper

1. Car jacked, wheel unlocked (so steering wheel turns), tire removed.
2. Position drain pan under caliper.
3. remove bottom caliper slide bolt. rotate caliper up, do additional testing to verify caliper is bad.
4. remove brake pads. They will fall out easily since they are held in place by tension only. don't lose metal guide clips.
5. loosen top caliper slide bolt. Slide caliper off, now caliper is free of disc completely.
6. Locate the "banjo" bolt (connects caliper to the brake hose). Loosen it. (this is how you disconnect brake line.)
7. pull out banjo bolt. it is hollow. the brake line banjo fitting will now fall away from the caliper.
8. there are two steel or copper washers, one on each side of the banjo fitting. Don't lose them.
9. you will lose a lot of fluid out of the brake line banjo fitting. if you can plug it temporary you will save fluid.