Pretrip on brakes

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Dumbitfown4me, Aug 21, 2019.

  1. Dumbitfown4me

    Dumbitfown4me Bobtail Member

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    Hi, I'm kind of new. Driving for one yr solo. I want to improve my pretrip on brakes. I look at them every day watching pad thickness, looking for oil stains, and making sure the pad is co acting the drum. I have some questions, and I addition any useful info is greatly appreciated, I'm here to learn. I'm simply not knowledgeable in mechanics beyond what I know in pretripping, so the simpler, the better.
    My questions
    Can you explain slack adjuster to me? Specifically self adjusting.
    How can you test if they are adjusted properly?
    Any other tips greatly appreciated pls educate me more on this
     
  2. bigkev1115

    bigkev1115 Road Train Member

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    One of the ways that you can tell if your brakes are adjusted properly is to roll a few feet and step on your brakes. If it stops smooth and quick, they re adjusted. If they try to keep rolling after you step on your brakes, then they are out of adjustment.

    On some trailers, if you pump the brakes, the slack adjusters will automatically adjust

    A lot of companies don t like for drivers to adjust the brakes.
     
    x1Heavy Thanks this.
  3. x1Heavy

    x1Heavy Road Train Member

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    For YOU... the nitty gritty does not mean anything. You don't touchadembrakes. Savvy?

    With that said, when I am at the DOT coop and Man is walking to where I am (Far end of spaces for trucks in inspection area, he has to walk and walk and walk... So I can maximize by service brakes to the floor flat hold a moment then let em up. Do it again Flat to the floor. With resolve each time. When I get about 6 or 7 applications Im pretty much out of primary air and low on secondary. He should be about halfway to me. He knows darn well what I did applying that much braking in a small amount of time. The slack adjusters generally fall into a better adjustment.

    I want to explain how you can use chalk and mark off one end of your pushrod from the brake can to your S cam actuator to your pads.

    However... things have changed since my time out there. In my day everything was manual where you needed either a half inch or 9-16th inch wrench to adjust the brakes until the drums quit singing and say thud. Then back off about half a turn on that bolt and your should get a singing drum. Set parking brakes and your drum should say thud to you meaning your brakes is applied. (It goes without saying you need to chock your truck and so on)

    with that in mind I'll leave automatic slack adjuster to someone else. I am not certified to adjust those. So I don't feel like I can safely try to explain with english words how to do it. Because from me it will get confused and not right. So with that thought in mind I leave it here.
     
    Concorde Thanks this.
  4. Broke_and_Hungry

    Broke_and_Hungry Light Load Member

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    X1Heavy is correct. There is code on who can adjust brakes. FMCSR 396.25
     
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  5. Dumbitfown4me

    Dumbitfown4me Bobtail Member

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    Aug 20, 2019
    Phoenix
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    I don't want to adjust them, I want to understand them better, and know how to tell if they are out of adjustment
     
  6. starmac

    starmac Road Train Member

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    Fairbanks Ak
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    Wrong Wrong, Stopping at slow speed tells you NOTHING about if your brakes are adjusted properly. If you pay attention to how much your air guage drops normally you can sort of get an idea if it drops a little more, the brakes may need adjusting.
    If by your self the easiest way is to have the rods coming out of the brake can marked when the brakes are released, some already have amark on them, others I put a zip tie on. now set your brakea and see how far the mark moved. Once marked all you hav eto do is glance at them anytime the brakes are set.

    It deppemds on what brand slack adjusters are on it, some adjust when applied, some when released, some adjust with as low as 10 pounds brake pressure others take a lot more.
     
    AModelCat Thanks this.
  7. Snailexpress

    Snailexpress Road Train Member

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    It's very good you want to learn. Here is link you can watch video explaining every part of air brake. If you want you can create account and get certificate after you complete to comply with federal requirements as brake mechanic. Bendix Commercial Vehicle Systems - Bendix Online Brake Training
     
  8. Blues Junkie

    Blues Junkie Bobtail Member

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    Jun 15, 2019
    Littleton, Colorado
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    If you have Drums.... you have brake shoes... not pads.

    Also if you set your brakes your slack adjuster should be at 90 degrees and when there off pull on your push rod and it should come out no more then an inch.
     
  9. starmac

    starmac Road Train Member

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    If you mark it, you don't have to pry them to see how much slack you have, usually do not even have to get under it.
     
    Blues Junkie Thanks this.
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