Manual Slack Adjusters
Manual slack adjusters compensate for the distance in the brake linkage by adjustments made with a wrench.
Automatic Slack Adjusters
Automatic slack adjusters remove the slack in the brake linkage without the need for manual adjustment.

Brake Adjusters

Slack Adjusters (also called Brake Adjusters or just Slacks) regulate the distance that the air brake has to travel to apply friction to the wheel. This distance increases as use of the brake causes the friction material of the brake shoe to wear away. When the brake is used, the operating rod pushes out on the Slack Adjuster which then turns the S-cam. The S-cam pushes the brake shoes apart which applies friction and slows the vehicle. Without this function, the air brake can become out of adjustment and the vehicle may lose its capability to slow or stop consistently.

When you need to replace your slack adjusters, it is very important to find the correct part that matches your equipment to ensure a safely operating braking system. It is easy to find the correct replacement Slack Adjusters for your truck, tractor or trailer. First, the type of slack adjuster should be considered. Slack Adjusters are available in two types, Manual Slack Adjusters and Automatic Slack Adjusters.

Both Manual and Automatic Slack Adjusters have three qualifications which can be easily measured. Finding these three measurements is the key to finding the correct slack adjusters.

Keys to Measure and Identify the Correct Slack Adjuster

Spline Teeth

The spline teeth of a Slack Adjuster fit into the spline teeth of the camshaft. Therefore, the slack adjuster and camshaft must have the same amount of teeth. A way to determine the number of teeth is to simply count them.

Spline teeth of a slack adjuster.

Arm Span

The arm span of a Slack Adjuster is the distance between the center of the camshaft and the center of the pin hole that is used with the clevis. Many slack adjusters feature multiple pin holes. These slacks can be used at any of the lengths available. For example, a Slack Adjuster with an arm span of 5.0 and 6.0 inch can be used in applications where a 5 inch or 6 inch arm span is needed.

This picture illustrates the arm span of a slack adjuster.

Camshaft Diameter

The Camshaft Diameter is size of the camshaft that fits the particular Slack Adjuster. This can be found by measuring the inside of the socket or the width of the camshaft.

Camshaft diameter of a slack adjuster

Popular Brake Adjusters for Heavy Duty Trucks and Trailers

Part #: SA22103 Slack Adjuster 1.5 - 28 Spline, 5 inch & 6 inch Span - SA22103
A Crewson Brunner type automatic slack adjuster with 1.5 inch Camshaft Diameter, 28 Spline, 5 inch & 6 inch Arm Span.
Your Price
$64.42
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$125.84
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$61.42
Part #: SA22102 Slack Adjuster 1.5 - 28 Spline, 5.5 inch & 6.5 inch Span - SA22102
A Crewson Brunner type automatic slack adjuster with 1.5 inch Camshaft Diameter, 28 Spline, 5.5 inch & 6.5 inch Arm Span.
Your Price
$64.42
List Price
$125.84
You Save
$61.42
Part #: SA21103 Slack Adjuster 1.5 - 10 Spline, 5 inch & 6 inch Span - SA21103
A Crewson Brunner type automatic slack adjuster with 1.5 inch Camshaft Diameter, 10 Spline, 5 inch & 6 inch Arm Span.
Your Price
$64.42
List Price
$125.84
You Save
$61.42
Part #: KN47001 Slack Adjuster 1.5 inch - 10 Spline, 5, 6 & 7 inch Span - KN47001
Genuine Haldex straight arm manual slack adjuster with 1.5 inch Camshaft Diameter 10 Spline, 5, 6 & 7 inch Arm Span. 1/2 inch pin size, straight zerk fitting, for Standard applications.
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Part #: CS52343 Slack Adjuster for 12-1/4 inch Brake 1.5 inch - 28 Spline, 5 & 6 inch Span - CS52343
Genuine Haldex automatic slack adjuster for 12-1/4 inch brake with 1.5 inch Camshaft Diameter, 28 Spline, 5 & 6 inch Arm Span. For Low Boy Applications, 5/8 inch - 18 clevis thread, curved offset.
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Part #: CS44071 Slack Adjuster 1.5 inch - 28 Spline, 5, 6 & 7 inch Span - CS44071
Genuine Haldex heavy duty straight arm manual slack adjuster with 1.5 inch Camshaft Diameter 28 Spline, 5, 6 & 7 inch Arm Span. For Meritor Applications.
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$36.02
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$33.24
Part #: 40020212 Slack Adjuster 28 Spline, 6 inch Span, 1.5 inch Camshaft Diameter - 40020212
Genuine Haldex self-securing automatic slack adjuster with 1.5 inch Camshaft Diameter, 28 Spline, 6.0 inch Arm Span. OEM #: 409-20006
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$92.91
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Part #: CS56040 Slack Adjuster 1.5 inch - 28 Spline, 5.5 inch Span - CS56040
Genuine Haldex automatic slack adjuster with 1.5 inch Camshaft Diameter 28 Spline, 5.5 inch Arm Span. For Truck/Tractor Applications, 5/8 inch - 18 & 1/2 inch - 20 collar lock thread.
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Part #: GS6000022825 Slack Adjuster 1.5 inch - 28 Spline, 5.5 & 6.5" Span - GS6000022825
A SORL manual slack adjuster, 1.5 inch camshaft diameter, 28 spline and 5.5 inch & 6.5 inch arm span. OEM quality replacement.
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$15.50
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Part #: KN52050 Slack Adjuster 1.5 inch - 48 Spline, 5.5 inch Span - KN52050
Genuine Haldex straight arm manual slack adjuster with 1.5 inch Camshaft Diameter 48 Spline, 5.5 inch Arm Span. 1/2 inch pin size, straight zerk fitting, for Ford applications.
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