The rear Toyota Brake Drums are the contact area where friction is created so the vehicle can be safely brought to a standstill. The brake drums on the rear of your Toyota are the components that have the wheel studs on them so the wheels can be firmly attached to them.
By providing a firm foundation for the wheel to be attached to, the friction created by the brake shoes in contact with the brake drums can control the stopping process of the vehicle. The only way the Toyota brake drums can be damaged is when the drum brake shoes are worn out and the padding has been used up exposing the inside of the drums to the metal backing plates of the shoes along with the rivets that hold the padding material in place. This metal to metal contact will cause grooves to be made in the smooth surface of the inside of the brake drums. The driver of the Toyota will be aware of this metal to metal contact when they hear a grinding sound upon the application of the brakes when the vehicle is in motion.
If these grooves are noticed during a brake replacement procedure on your vehicle, the brake drums will need to be turned on a lathe. This will makes the surface smooth again but at the same time reduce the thickness of the drums on your Toyota. This can only be accomplished if there is sufficient thickness to the drums and not making them too thin. The drums are the place where friction is created in stopping the vehicle. This friction creates heat. If the walls of the drums are too thin, the heat cannot be properly dissipated and the brakes will overheat causing a brake failure to occur.