What You Need to Know About Manual Slack Adjusters

Purchasing a manual slack adjuster can help you in a variety of ways. There are a few things that you need to know about this type of equipment. These include its functions and problems.
Automatic slack adjusters vs manual slack adjusters
Whether you love or hate automatic slack adjusters, there's a good chance you've seen them. They're a standard part on heavy-duty trucks. They help maintain the proper clearance between the brake drum and the lining in the brakes, reducing the risk of over-stroking the brakes. They're also designed to adjust themselves during full brake applications, which eliminates the need for manual adjustments.
There are many types of automatic slack adjusters, and not all of them are the same. For example, one may be offset, while another may have a clevis pin. In general, they're all designed to perform the same function, but the best ones are also the most reliable.
There are two main types of automatic slack adjusters: stroke sensing and clearance sensing. The latter type is designed to maintain the nominal distance between the brake lining and drum, while the former is a measurement of the stroke of the pushrod.
Automatic slack adjusters are required in vehicles manufactured after 1994. They're also mandated in South Africa, where they're required in trailers with a gross vehicle mass (GVM) above 3500.
While automatic slack adjusters are an essential part of the heavy-duty PM program, there are a number of factors that can cause the brakes to go out of adjustment. The most common is over-adjustment, but there may be other factors involved as well.
Functions of a slack adjuster
Whether you have a manual slack adjuster or an automatic slack adjuster, you should know how to adjust it properly. This way, you can keep your vehicle in optimal braking condition.
The slack adjuster is a mechanical link between the brake chamber and the brake actuating cam. It has a spline that is attached to the foundation brake cam shaft. The slack adjuster adjusts the gap between the brake drum and the brake shoe lining. It is designed to compensate for gradual wear on the lining.
The slack adjuster also maintains the proper stroke of the brake lining. This is important because an insufficient actuator stroke can have negative effects on the braking power of the vehicle. When a manual slack adjuster is installed, it is generally required to be adjusted periodically.
Slack adjusters are typically installed on commercial vehicles, such as trucks and buses. In North America, trucks and buses account for a majority of the commercial vehicle market. Increasing sales of vehicles in this region is one of the major drivers behind the rise in slack adjuster market.
Several countries are imposing regulations to promote the use of automatic slack adjusters. In Canada, all new equipment manufactured after 1996 must be fitted with automatic slack adjusters.
The most common problem that is found during roadside inspections is out-of-adjustment brakes. These are not necessarily caused by any problems with the ASA itself, but rather by other brake hardware that is at fault.
Problems with a manual slack adjuster
During a roadside inspection, a manual slack adjuster can be one of the first mechanical problems found. Most often, it is due to operator negligence or a problem with a part outside of the adjuster.
The slack adjuster is found between the S-cam and the pushrod on drum brakes. It is designed to take up slack in the brake stroke when friction surfaces wear away.
The slack adjuster should be greased before use. The high-temperature waterproof grease should be NLGI Grade 1, free from fillers and abrasives. It should be lubricated until grease is forced through the gear splines around the inboard snap ring.
The pushrod should be checked to ensure that it is straight. If it isn't, it could be a problem with the brake assembly or a foundation brake component.
The slack adjuster can be adjusted manually by turning the hexagon nut on the body of the adjuster clockwise. This should be done only in an emergency situation. It can also lead to further mechanical problems if it is done improperly.
Manual adjustment of ASAs should only be done by a trained technician during the installation. Failure to do this can cause over-stroking of the brakes, which is another mechanical problem.
If the manual adjustment of the ASA does not cure the problem, the ASA should be taken to a repair facility. This may be necessary if more than 25% of the wheel-ends are out of adjustment.
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