Brake adjusters play a crucial role in maintaining proper brake function on heavy vehicles. Regular inspection of these components is essential for safe vehicle operation.
Auto brake adjusters have greatly improved the reliable function of these braking systems. However, there are important things that a technician needs to be aware of to ensure they continue operating effectively.
Let’s look at a few tips that will ensure reliable and durable brake adjuster operation.
The most important piece of advice, that is often ignored, is do not adjust an auto brake adjuster other than on installation or brake reline.
Some technicians, often ones that have been in the industry for years, will tighten and back off the brake adjuster every service, just as they have been doing with manual brake adjusters.
However, regularly adjusting an automatic brake adjuster can cause premature wear on internal components and could lead to the adjuster becoming inoperable.
On the other hand, if an auto brake adjuster is out of adjustment, then the cause needs to be investigated and repaired. There are many issues that can cause an auto brake adjuster not to operate correctly. Manually adjusting the auto brake adjuster will not correct any of these.
The most basic check is that of brake adjuster free stroke, which is an indication of necessary brake shoe clearance. Hendrickson uses the Haldex S-ABA automatic brake adjuster that uses free stroke clearance as a basis for self-adjusting. When free stroke becomes greater than a certain amount it will move the adjustment up.
To check free stroke, add a brake check gauge or mark to the brake chamber rod. Use a bar or lever to move the brake adjuster from the full retracted position until the shoes contact the drum. Measure this movement to determine the free stroke. If this measurement is between 10 and 16 mm, then the basic adjustment is correct, and the brake adjuster is doing its job.
If there is excessive free stroke, inspect the adjuster for installation issues, the adjuster anchor grommet for excessive wear and verify that the adjuster anchor is properly secured and correctly installed.
With this basic check carried out, the technician can move onto checking the brake applied stroke, inspecting foundation brakes, friction lining material, drum surface and wear limits, brake chamber mounting, and other brake components for wear or damage.
Another item that is easily neglected is that of lubrication. Different manufacturers have different grease and greasing intervals. Avoid using moly (molybdenum disulfide) grease in Haldex brake adjusters, as it can potentially interfere with operation of the internal friction clutches and compromise the automatic adjustment’s reliability. It is important to follow the lubrication specifications for the specific brake adjuster installed on the vehicle.
By regularly inspecting the free stroke without adjusting the auto brake adjusters, technicians can ensure that the braking system operates reliably and efficiently.
Appropriate maintenance of brake adjusters not only enhances vehicle safety but also extends the life of the brake components, ultimately reducing maintenance costs and downtime.
