Air Brake Adjustment

I think '96 and newer have to have auto slacks........fyi

 

There are several different types. One type I'm familiar with uses a 9/16 wrench. I was taught, put it on a "bolt" that is on the adjuster. Tap the wrench in place to release the "bolt" from a keeper. With the brakes released, tighten the brakes tight against the drum. Then back the bolt off 1/2 turn.

Easier done than said!

 

They didn't teach you how to adjust brakes because there are very few manual adjusters on trucks any more.

Since you have a 99% chance of getting a truck with automatic slack adjusters, here's how you adjust them: Push in your brake knobs. Stand on the brake, exerting no less than 90 pounds of pressure for not less than 15 seconds. Release the brakes. If they are not properly adjusted after doing this, they need professional attention.

This may be a FOAF story (friend of a friend) but I know a guy who was told his brakes were out of adjustment. He went under the truck to adjust them himself. As soon as he applied the wrench, the DOT guy asked for his brake certification card. Naturally, he didn't have one. He got a ticket.

I do not apply tools to my own brakes. The liability is too high. I don't want to be sued if something goes wrong after I adjust them. I'd just a soon let that fall to someone else who is certified on brakes.

 

1994

 

You got it right Injun and the certified brake card is not a myth, I have one as it shows you are properly trained to inspect and adjust your brake but you shouldnt adjust automatic slack adjusters. Most companies stopped this as they have found that there are problems (if needing adjusting all the time) with the brakes itself. They also dont usually give it to rookies fresh out of school. BTW I do the same method as injun for adjusting my auto slack adjusters except I do it twice in a row. The reason for doing this is you normally dont apply that much pressure to your brakes so they never get adjusted properly

 

She's right, you must be trained and certified plus carry a card or it's ticket time. ( If the bear sees you , admit nothing ! )

The old ones are like they said, 9/16 box end, apply the wrench, push the lock down and turn till shoe snugs drum, back off 1/4 on center axle and 1/2 turn on rear axle of tractor / trailer. That will keep them from smokin the tires when empty.

And thanx Injun for the tip on the auto adjust, I didn't know that but I'll try it....

 

Regarding how long the travel is before a mechanic is needed: On the older ones (year, anyone?) it was one inch. On the newer ones (long travel slack adjusters) it's three inches.

 

When I'm sitting at a stop sign or stop light, nothing else to do, will stand on the brakes to 85 psi (they don't go higher) a couple times keeping an eye on the air tanks pressure doesn't go below 100 psi. Also end of the day every day, day in and day out lol full on air brake test with bleed down/pop out and drain tanks.