What Are Slack Adjusters?

How Slack Adjusters Help Stop Your Semi-Truck

Have you been wondering what you can do to make sure the slack adjusters in your air brakes are up to par? If so, you've come to the right place! Read on to learn more about slack adjusters, how they work, how to adjust them, and what you need to do to ensure they are operating properly. Our expert trucking specialists have put together the following guide to help you increase your knowledge on the subject including this Slack Adjuster Cross Reference Chart.

What are Slack Adjusters?

Your semi-truck's air brake system features a complex array of moving parts. It's typically made up of hundreds of components, including your slack adjusters. If you have a semi-truck, then you probably have an air brake system with slack adjusters installed. In 1994 it was mandated that slack adjusters become standard in semi-truck air brake systems, and since then, all trucks use them.

But what are slack adjusters? Slack adjusters are lever arms connected to the brake chamber's push rod located the clevis assembly. Though they are just one small piece of the larger puzzle, slack adjusters are an integral part of your heavy-duty truck's air brake system.

Simply put, Slack adjusters are the mechanical link between the brake chamber's push rods and the camshaft. The entire slack adjuster works as a unit, rotating with the camshaft as the brakes are applied or released. This means that the slack adjuster is a component of your air brake system that needs to be well maintained and checked regularly.

How do Slack Adjusters work?

You may be wondering how slack adjusters work within your air brake system. The answer is less complicated than you might think. Slack adjusters adjust the brakes to make up for wear on the lining. When the brake is applied, a rod pushes out the slack adjuster. The slack adjuster then turns the s-cam, which forcing the brake shoe apart. Then, the mechanism applies the force necessary to stop a truck.

What's the Purpose of a Slack Adjuster?

Slack adjusters are made to serve three very specific purposes. First, modern slack adjusters are designed to convert the forward linear motion of the push rod into the rotary motion of the camshaft. Slack adjusters also act as a lever that generates force and applies it to the brake discs. Finally, they provide a means of lessening the distance between the brake shoes and the brake drum, providing drivers with more responsive braking.

What kind of slack adjusters do I need?

Available in in a variety of arm lengths, configurations, torque ratings, and spline types, there are slack adjusters available for every kind of truck. However, there are two kinds of slack adjusters you'll want to think about when working on your truck – automatic and self-adjusting.

Automatic slack adjusters automatically keep brakes in proper adjustment. They are designed to compensate for brake lining and drum wear in order to maintain a constant actuator stroke. Automatic slack adjusters need to be checked regularly to ensure they are maintaining proper push rod travel. With automatic slack adjusters, you don't have to make manual adjustments. This is a definite advantage over self-adjusting slack adjusters.

How do you check your slack adjusters?

First, make sure your truck is parked on level ground. Then you'll want to turn your parking brake off, so the slack adjusters can be moved. You will also want to set wheel chocks behind the tires. The next step is to pull on each slack adjusters, and if it moves more than an inch where the adjuster meets the push rod, then you will probably want to make adjustments to the mechanism.

Shop Slack Adjusters

Is your heavy-duty truck in need of new slack adjusters? If you are looking for aftermarket slack adjusters for your semi truck's air brake system, we have everything you need. With a full line of slack adjusters and semi-truck parts, we are happy to be your one-stop shop for everything you need to make sure your truck's air brakes system is running at peak performance. If you have any questions about air brakes or slack adjusters, feel free to contact us using our online form. Our product specialists are here to make sure they are all answered.

1. Haldex AA1 Automatic Slack Adjuster - 40010140
2. Gunite 5.5in. Automatic Slack Adjuster - AS1140
3. Autocar AA1 Automatic Slack Adjuster - A7540001-001
4. Gunite 5.5in. Automatic Slack Adjuster - AS1132
5. Gunite 5.5in. Automatic Slack Adjuster - AS1172

Do you want to learn more about air brakes? If so, take a look at our guide on how to maintain your air brakes.