Slack adjuster check

This one is a bag of tricks, at best.

Auto adjusters, should not be adjusted manually. So they say. Most adjust in one of 2 ways.

#1 A quick roll in reverse, then apply the brakes. Hard

#2 Apply the brakes, some auto adjust operate like ratchets. They take the slack out the first time, then you have brakes on the second stab. Never understood that one myself. But I'm no mechanic.

Manually, I would say the majority of us old school drivers, simply adjust the brakes until they seat against the drum. Then back off a quarter round. Be sure to chock your wheels before you attempt this. You wouldn't want it to roll while you were making this adjustment.

Disc requirements are different, as some have locking nuts on them. I assume you are referring a drum.

Of course, that's not completely "correct". As most DOT use a simple gauge to check for even clearance and wear around the drum. Your company, like most. Did not issue you one of these gauges. So it's hit or miss.

BTW, these adjustments can't be made while the brake is set

 

Slack adjust should have no more than 2 inches of play.


From the way I was told the legal and rght way is this.

Park the truck on level ground, chock the wheels.

Chck how much play the slacks have by having someone step on the brake. If more than two inches then tighten all the way and go back 1/4 turn.

U need two people for it, but if you could keep the brakes down with a pole then you can do it by yourself with say putting a marking on the slack .

Hope this makes sense I am typing this from my phone

 

The Michigan CDL manual states that "if a slack adjuster moves more than about one inch... it probably needs adjustment."

The North American Uniform Out of Service Criteria shows the maximum stroke at which brakes must be adjusted. Depending on the design of the brake chamber, measurements vary from 1.25 inches to 2.75 inches.

If one brake is 1/4 inch or more beyond the readjustment limit, it is a defective brake. If the number of defective brakes is equal or greater than 20% of the brakes on the vehicle or combination, it constitutes a defective brake system.

If two brakes are at the readjustment limit or less than 1/4 inch beyond the limit, this equals one defective brake.

When adjusting drum brakes, always tap the drum after backing off the adjustment. If it rings like a bell, the shoes are not dragging. If there is a dull thud, back it off some more.

 

I don't understand how "roll in reverse..." would have any effect on slack adjusters. "Roll in reverse" is for automobiles.

http://www.di-pro.com/slackadjuster2003automaticfunction.htm

 

our company manual says the automatics do not adjust from (normal stopping pressure).

policy now is to apply 80psi of application pressure, while already stopped.

I suppose they had to add that (while already stopped) for a reason??? LOL

apparently normal stopping pressure is 12-20psi and it just isn't quite enough to keep things adjusted.

each to his own...

 

One thing that is very important if you crawl under the truck. TAKE THE KEY WITH YOU. If there's more than one key then take the key and leave a note where you'll know for sure another driver will see it.

 

When I was taught my pretrip I was told I must check my slack adjuster for no more then 1 inch of free play at the pushrod when brakes are engaged...