In order for heavy vehicles, such as trucks, to slow down, air brakes are used. One important component of air brakes is slack adjusters. Let’s learn more about this important part of a truck’s mechanism.
What are slack adjusters: Within the braking system of a truck is a slack adjuster. This metallic arm connects the camshaft and the brake rod and maintains equal pressure so that there isn’t extra wear on the brake pads. A benefit of an automatic slack adjuster is that you don’t need to inspect it as often as you would a manual slack adjuster.
What do slack adjusters do?
The purpose of slack adjusters is to be a mechanical link that connects the camshaft and the brake rod in a brake. They are needed to maintain proper brake chamber stroke, which essentially means they keep everything in working order with your truck’s brakes.
Slack adjusters look like metallic arms and come in different sizes, depending on the construction of the air brake system. They are important as they adjust the brakes, as the name suggests so that there is no wear and tear on the lining of the brakes.
As for specific functions of slack adjusters, above all else, they make it easier for a driver to brake. This is because the distance is shortened between the brake drum and the shoes, allowing drivers to have more control over their braking, which ultimately improves safety.
Where can you find slack adjusters?
To locate your slack adjusters, take a look at your braking system. The metal arms are located between the camshaft and the push rods.
How do you set up slack adjusters?
While your slack adjusters will already be installed in your braking system, you should periodically inspect them, as you would with other parts of your truck’s construction.
Types of adjusters
Manual adjusters
While all new trucks, especially those produced after 1994, have automatic slack adjusters, older models that are still on the road may have manual slack adjusters. These work in a similar manner but require more maintenance.
Generally, you should inspect your manual slack adjusters every 10,000 miles. To inspect your slack adjusters, start by parking on a flat service. This will guarantee easier access.
Be sure to engage your parking brake, not only for safety, but so that you can access the braking system, which you can’t do if it is engaged. Finally for setup, place wheel chocks behind your tires for an extra layer of precaution.
Gently pull on the slack adjusters. You may want to wear gloves so your hands don’t get dirty.
If the slack adjusters move more than an inch, particularly in the area where they meet the push rods, then it means they need to be adjusted.
Automatic adjusters
The beauty of automatic slack adjusters is that they do not need a lot of maintenance. In fact, they are created so that they will adjust on their own, accounting for new brake lining wear.
Most newer truck models will have automatic slack adjusters so try to resist the temptation to adjust them on your own. Doing so can actually cause more issues.
Instead, if you are worried about your automatic slack adjusters, have a mechanic inspect them. If you or a mechanic are performing a complete brake overhaul, this would be the time when the slack adjusters would be looked at in more detail.
If you do need to tinker with the automatic slack adjusters, proceed with caution. Using a heavy-duty tool, such as an impact wrench, can cause internal damage.
You can also add extra grease to automatic slack adjusters to help with lubrication. Furthermore, the adjustment arm should be fitted into the bracket in a firm manner. This will hold everything tight and ensure the slack adjuster doesn’t produce more wear on the brake pads.
How much play is allowed in a slack adjuster?
The ideal play, or amount of movement you can have with a slack adjuster, is less than an inch. If you can, make sure it is between 3/8 and 5/8 of an inch.
If there is too much room for movement, it means the slack adjusters aren’t working properly and won’t be able to help with the braking system.
Are slack adjusters mandatory?
All modern trucks will have slack adjusters in their air brake system. This is because federal guidelines made them mandatory in 1994. Slack adjusters play an important safety function which is why they are so important.
While you could have manual slack adjusters in your vehicle, the better choice is automatic slack adjusters. They require less maintenance and don’t need to be inspected as often as manual slack adjusters.
Other types of adjusters
There are many moving parts within a brake system and many of these parts are termed an adjuster. Here are some terms that are often associated with slack adjusters.
Clearance adjuster
In order to keep a standard space or clearance area between the brake drum and the lining, a clearance adjuster is used. This allows the wear on the brake to be consistent so that one part doesn’t wear down faster than the other.
The clearance adjuster works by disengaging once the brake drum meets the lining. As a result, when the automatic slack adjuster kicks in, the braking system isn’t affected by whether the driver puts more effort into braking or not. Essentially, a clearance adjuster helps for more even braking, regardless if the driver has to step on the brake pedal or ease into it.
Stroke adjuster
Another helpful part that maintains even pressure through the braking mechanism is the stroke adjuster. Again, this part will control the pressure on the brake, whether the driver brakes softly or in a hard manner.
Conclusion
While there are many complicated parts in a braking system, a slack adjuster is one of the most important. Older trucks relied on a manual slack adjuster while newer ones have automatic slack adjusters, which don’t require as much maintenance or inspections.
