It is important to remember to follow drum brake inspection top tips and bear in mind that the drums have a design feature that significantly reduces dirt contamination. The closed assembly is less vulnerable and ideal for off road conditions.
However, a drawback is the lack of heat dissipation which creates more heat build-up during repeated high-speed braking. Even with the benefits, periodically inspecting and maintaining the brake system is important to the unit’s operation and is critical to road safety.
Please note that the following instructions are general in nature. Actual inspections should be performed as per the brake manufacturer’s service manual.
Upon initial inspection, apply the parking brake, remove the inspection grommet from the dust cover and review the brake lining thickness. Brake drums and linings will typically have a visible wear step which indicates they are due for replacement. While the parking brake is applied, inspect the brake chamber pushrod to determine if the pushrod over stroke indicators are visible. Refer to the original equipment manufacturer (OEM) service material for correct pushrod length and measurement criteria.
With the drums removed look for any signs of excessive heat loading, cracks, and uneven wear. Measure the drum wear with a brake drum gauges to determine if it is out of round. If replacing the brake shoes, look over the anchor pins, rollers and s-cams for signs of abnormal wear. Its best to replace the pins, roller bushes, and springs whenever replacing the brake shoes.
If replacing the anchor pin bushes, do not use an excessive amount of force as it could cause damage to the spider plate. Ensure all of the dirt, dust, and old lubricant is thoroughly cleaned off before applying new anti-seize compound to the pins, roller slots and the ends of the roller (doing so will prevent incompatibility concerns between different lubricants). For units operating in a dusty environment, the use of a dry film lubricant is highly recommended.
S-cam axial and radial play should be measured to determine if adjustment or replacement is required. The s-cam tube will need to be greased until fresh grease is seen coming out of the seal. In addition, the slack adjuster will also require greasing and proper adjustment as per the OEM specifications. If the slack adjuster is ever removed, ensure the splines are lubricated with suitable anti-seize compound and the correct angle is set.
Prior to drum installation, clean the mating surfaces to remove any dirt or corrosion from the hub flange, drum face, pilot, and wheel contact area. If this is neglected, then the drum will not seat properly and may cause cracks at the drum flange. Cleaning the wheel mounting face is also important to prevent wheel runout, wheels coming loose, or any relative wheel movement.
In addition to following through with the designated service intervals, keeping a log is generally good practice. Tracking the inspections and repairs performed will provide an indication of the brake service life and prevent costly roadside failures.