How do you adjust the trailer brakes?

Discussion in 'Experienced Truckers' Advice' started by expedite_it, Jan 18, 2025.

  1. expedite_it

    expedite_it Road Train Member

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    Preface to thread: There is a truck repair subforum at thetruckersreport.com, but there is not a trailer repair subforum at thetruckersreport.com. So that is why I posted this thread here at "Experienced truckers' advice".

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    Several times in my career I have been hooking to a trailer on a drop & hook, and the trailer brakes the trailer that I am hooking up to won't grab hard enough to slide the tandems. I will pull out the tandem release button to release the trailer tandem pins, and the pins will retract, but when I move the truck backwards with the red brake valve pulled out, the trailer wheels will roll backwards. So I cannot slide the trailer tandems forward because the trailer brakes won't grab even though I have the red brake valve pulled out. When this happens, I call Breakdown at my company, and Breakdown sends out a mobile mechanic to repair the trailer. This is time-consuming. If the wheels are not turning, I am not earning. It occurred to me that I would probably make more money in the long run if I was able to adjust the trailer brakes myself.

    When your trailer brakes don't adequately stop your trailer wheels from spinning, do any of you adjust your trailer brakes yourselves?

    What tools do you have to have to adjust your trailer brakes?

    How do you adjust your trailer brakes to make it so that the trailer wheels won't spin when the red brake valve is pulled out?
     
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  3. Sons Hero

    Sons Hero Road Train Member

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    If it has drum brakes, a 9/16” wrench, or a vise grip. I have never pulled a trailer with disc brakes, not sure about them. There are probably about as many proper ways to do it right as there are mechanics, the way I do it, release your brakes, crank the slack adjuster tight, then back it loose a quarter turn. If you ever adjust your tractor brakes, do it just the same, only give it an extra 1/4 turn on the steer axle. I don’t like my front wheels grabbing harder than the drives.
     
  4. RockinChair

    RockinChair Road Train Member

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    I always try backing up and using the trolley valve a few times to make the slacks self-adjust. But if that doesn't work, use the wrench method @Sons Hero mentioned. You could also chock the tires to help with traction while sliding the tandems.
     
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  5. kwswan

    kwswan Road Train Member

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    Depends on whether they are manual or automatic slack adjusters. This works for manual ones.
     
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  6. tscottme

    tscottme Road Train Member

    I always, back in the day, just used a7/16 or 9/16 in wrench, tightened the brakes down & then backed them off a certain amount. I don't recall how much I backed off the brakes. This was before automatic slack adjusters were the norm. If I recall whoever was doing the brake adjustment needed some training on the proper technique to be legal.

    It could be the trailer brakes are out of adjustment or air pressure isn't sufficient for brakes to grab hard enough for sliding tandems. Look at all 4 tandem pins and make sure they all show a gap between the pin & frame on the same front or back of all of the pins. I've had trailers that might be bent & this made it ver difficult to release tandems.
     
    Last edited: Jan 18, 2025
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  7. expedite_it

    expedite_it Road Train Member

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    I don't have a trolley valve. I drive a company truck at a mega.

    I have @Sons Hero on ignore. He is on ignore for a reason. I don't want to see what he writes.

    I know that I could chalk the tires, or sometimes I could back the tires up against a curb. But I want to learn how to adjust the trailer brakes myself.
     
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  8. expedite_it

    expedite_it Road Train Member

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    What does air pressure have to do with this? I thought that when the red brake valve is pulled out, the force that causes the trailer brakes to grab is made by a spring.
     
  9. Diesel Dave

    Diesel Dave Last Few of the OUTLAWS

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    If it has automatic slack adjusters, sometimes they quit working. If so, you can do the same as mentioned above but the wrench size is a 7/16. And it might slightly hard along with a ratchet sound. Tighten up, back of about a 1/4 to 1/2 turn and tap on the drum with the wrench, the idea about the tap on the drum is to listen to the sound(pitch), so the others have the same sound.
     
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  10. Sons Hero

    Sons Hero Road Train Member

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    I willingly give logical answers to logical questions. Stupid questions, Get stupid answers. Sleep well
     
  11. expedite_it

    expedite_it Road Train Member

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    I don't even know how to tell if the trailers I pull have manual slack adjusters or automatic slack adjusters.
     
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