The following was published in CCJ’s Air brake book11th edition, sponsored by SilverbackHD. CCJ‘s Air brake book is a complementary industry resource thanks to our partnership with SilverbackHD, the Technology and Maintenance Council and the Commercial Vehicle Safety Alliance. You can Download the entire Air Brake Book here.
The following guidelines, compiled from fleet managers and field service representatives, can help you make more informed ABA maintenance and purchasing decisions:
When purchasing ABAs:
Request evidence of a potential ABA’s performance in different climates, applications, occupations, and geographic regions similar to those in which you work. Keep in mind that a manufacturer may have more than one ABA offering, including a unit better suited to your operation.
Since internal contamination is an ABA’s number one enemy, ask how the ABA you’re considering is sealed to keep moisture and contaminants out.
If your trucks will be used in rough or mountainous terrain, pay special attention to how the manufacturer has addressed over-adjustment issues and how the design compensates for them.
When you’re retrofitting, don’t just buy based on price.
If you’re not sure which ABA to use, buy a few, install them, and track their performance before committing to a big purchase.
Compare preventative maintenance requirements and on-site serviceability characteristics between multiple ABA brands before purchasing. Some ABAs may require special lubricants to work properly. If you work in difficult conditions, devices with easy replacement characteristics may be preferable.
If you have problems with camshaft corrosion, consider specifying an ABA with a lubrication system that sends grease to the splines at every service.
Consider visual shot indicators to monitor the performance of your ABAs.
When servicing ABAs:
Be sure to include ABA inspection procedures in your maintenance plan just like any other component.
Although manual slack adjusters are becoming increasingly rare, remember that manual and automatic units should never be used together on the same vehicle. Also, some manufacturers warn against using ABAs from different manufacturers in the same vehicle. There is general consensus that they should never mix on the same axis.
• Improper factory ABA installation can be a problem on new vehicles. The ABA inspection should be part of your basic pre-delivery vehicle inspection.
• When converting older vehicles from manual to automatic adjusters, ensure technicians receive thorough training and are familiar with each type of adjuster. Compare installation requirements and interchangeability with the manual adjusters on the vehicles and suspensions you are installing them on. Do not rely on installation diagrams that represent a “typical” vehicle.
• Remember that ABA bodies are larger than manual adjuster bodies and ensure that there is adequate suspension play when the adjuster body is rotated at maximum chamber travel.
• Remember that some ABAs fit better under some mounts than others. Some require left or right handed versions with an offset clevis or arm to fit.
• Remember that moving from manual adjusters to ABAs can reduce some brake maintenance costs by reducing the frequency of human intervention in the brake adjustment process and reducing uneven pad wear from wheel to wheel. However, ABAs do not reduce the need to perform other brake maintenance. In fact, the use of ABAs actually increases the need for optimal brake system maintenance and performance as they tend to reinforce weaknesses in brake maintenance practices and procedures. In short, for ABAs to work properly, brakes must be maintained at optimal levels. This can increase brake maintenance costs in some fleets, but pays off in safer vehicles and less unplanned downtime.
• Always use the same type and brand on each axle to avoid side-to-side braking performance problems.