As the overheated drums expand, the brake shoes and linings have to move farther to contact the drums, and the force of this contact is also reduced. Continued overuse may increase brake fade until the vehicle cannot be slowed down or stopped at all. Brake fade is also affected by adjustment. To safely control a vehicle, every brake must do its share of the work. Brakes out of adjustment will stop doing their share before those that are in adjustment.
Brakes can get out of adjustment quickly, especially when they are hot.
Therefore, brake adjustment must be checked frequently. Apply the brakes just hard enough to feel a definite slowdown. You now apply the brakes hard enough to gradually reduce your speed to 35 mph and then release the brakes. Repeat this as often as necessary until you have reached the end of the downgrade. If the low air pressure warning comes on, stop and safely park your vehicle as soon as possible.