Brake chamber stroke to long help

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Mr79W900A, Jun 16, 2021.

  1. Mr79W900A

    Mr79W900A Light Load Member

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    Shop changed my brake chamber the other day so I was under the truck and noticed when it’s released it’s the same length as the rest but when applied its 5-1/2 inches long versus all the others at about 3-1/2. What’s going on here. I get it seems long but if I cut it down it looks like it’ll will push to far in when released. Brakes are type 3030 reg stroke round port. Chamber is the correct one.
     
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  3. God prefers Diesels

    God prefers Diesels Road Train Member

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    When released, it goes "all the way". But when applied, it will move until the shoes contact the drum. Seems like you need to cut two inches off, install it, and then readjust your shoes on that corner.

    But you seem to know what you're talking about, so is that even possibly the problem? Did you already rule that out? When they're released, do the brakes on that corner have a larger gap than the rest? Have you already adjusted them?

    @AModelCat
    @Rideandrepair

    A few guys on here that know air brakes better than they know how to walk, but I swear I can't keep everyone straight.
     
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  4. Mr79W900A

    Mr79W900A Light Load Member

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    When applying the brake the rod comes our way to far. Whole chamber is new so I’m thinking maybe the slack adjuster is pooched.
     
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  5. God prefers Diesels

    God prefers Diesels Road Train Member

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    It's splined, and I'm pretty sure if you break the inside part while manually adjusting, it just won't self-adjust anymore. When you installed the new chamber, did you cut it the same length as the old one? And if you did, did you adjust your brakes afterward? I know that might be a stupid question.
     
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  6. Rideandrepair

    Rideandrepair Road Train Member

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    Sounds like it needs to be adjusted. Tighten up the little 5/16, or 3/8” adjuster, till it’s tight. She’s touching drums, then back it off 1/2 tug depending on what type you have, might have a little lock button to release to back it off, Other kind, you just crank on it, it ratchets out, quite a bit harder and louder than when you tighten it.
     
  7. Mr79W900A

    Mr79W900A Light Load Member

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    Th
    They are auto slacks forgot to mention
     
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  8. AModelCat

    AModelCat Road Train Member

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    Still will require an initial adjustment even if its an auto slack adjuster. I'd start with with adjusting it manually and see how it looks.
     
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  9. Rideandrepair

    Rideandrepair Road Train Member

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    Good question. I think since they’re all the same length, released, the rods the correct length. Slack just needs adjusting. Too much stroke. When applied should have less than 2” max stroke. 1-1.5” is good. So release Tractor brakes, chock wheels, or set, trailer brake. Or disconnect trailer brake lines. If you’re hooked to a trailer. Don’t get run over. Tighten slack, and back off. You can mark them. Or use a piece of tape, when released. Then set brakes, and measure the stroke, if you want exact measurements. If it’s your Truck, I would just adjust them all, should be fine. You can keep an eye on it, make sure it’s holding adjustment over a few weeks or next couple months even, just to make sure, one or more aren’t bad. They just forgot to adjust the slack.
     
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  10. Rideandrepair

    Rideandrepair Road Train Member

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    The new chambers come with a tag, that explains stroke. Total stroke is something like 3-3.5”, maybe? II forget excactly. So ideally the rods out 1/2”-34” maybe when parking brakes released. Then when adjusted within 1.1/2 stroke, you still have some rod left, should it get out of adjustment. So if total stroke is 3.5” say, you can have a 3” stroke, and brakes will still grab barely. Bottom line, if the rods a little bit too short,or too long, they still work fine if within the 2” max stroke. That’s from rough memory on my part. The tag, explains it all. As long as they all look the same, released. They’re probably just fine. New rod should be the same length as the others. The long stroke your seeing when applied is taken up by the slack adjuster. First manually, then automatically each time you hit the brakes, one 1 or 2 clicks at a time. On my Trailer, I had 4 different rod lengths , from having them replaced so many times. I had no idea which was the correct exact length. Since I was replacing all of them, I started from scratch measuring, following the directions. In your case, the length is probably fine, if it matches the others.
     
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  11. Rideandrepair

    Rideandrepair Road Train Member

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    I hope I didn’t just totally confuse you. Lol. I honestly never knew exactly how the length was determined. Till I did mine last summer. The tag basically explains how to measure and cut the length. Too long, they’ll apply past a 90 degree angle. Too short, might not make contact, if it gets out of adjustment, and shoes/ drums are thin. So when applied the rod and slack should be just under 90degrees. Like 80-85 degrees. Basically at an L shape angle, any more risks braking power loss. That’s how I read it anyway.
     
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