What causes screeching brakes ?

Brake squeal is the subject.

 

It’s probably just surface rust on the drums. Happens on all vehicles. Drums, rotors. New or old. The term rust jacking, is a description of rust between the lining of the shoes and the shoes themselves. Often it causes cracks near the corners, or edges. It’s acceptable, unless the linings are cracked completely across the shoe. A squeak that’s only heard when brakes are first applied, and goes away, is usually caused by rusty bottom anchor pins. A very common thing, as they often don’t get changed with the brake job. Because they’re rusted in place, but not worn. A visual inspection of shoes and drums, from underneath the Truck of shoe thickness, and a feel of the drum, by running your finger inside it, will tell a lot. They’re either legal or not. Might have heat glazed shoes on one or all of them. If so, the drums will probably also be grooved excessively. Easily felt, by checking them by feel. Re using grooved drums with new shoes will make the surface rust squeak worse. Goes away after a while, once the surface rust is gone.

 

If it’s that bad, maybe one or more aren’t making full contact. Out of adjustment, or bad s cam bushings, making them not apply fully, or applying at an angle. Worst case scenario is a bent spider, causing the shoes to apply at an angle. That can be seen from underneath. The shoes should fit evenly inside the drums.