For certain air parking brakes, the wheel cylinder boots may fail to maintain air-tightness due to improper installation and allow water to enter inside. If this occurs, the draw rods or the wedge rods may rust, which could cause the sliding sections of the draw rods not to move smoothly resulting in reduced braking efficiency, and at worst, one of the wedge rods could break, in which case the parking brake of that wheel would not work, greatly reducing braking efficiency.