Uneven wear on drives brakes

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Qbf594, Jul 8, 2020.

  1. Qbf594

    Qbf594 Medium Load Member

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    Newer driver of big trucks here...
    My 2020 international just rolled over 100,000 so when I was having a trailer tire swapped I asked the mechanic to check the drive brakes. He confirmed what I thought I was seeing. Axle 3 is definitely wearing faster than axle 2.
    How does this happen? I thought they adjusted themselves...
     
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  3. Maxiepad

    Maxiepad Bobtail Member

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    Google how to adjust. Your truck brakes .for year model .it's usually going foward or backwards at 15 mph and locking them down to stop repeatedly.not letting off till stopped.
     
  4. Maxiepad

    Maxiepad Bobtail Member

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  5. AModelCat

    AModelCat Road Train Member

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    Could be a multitude of things:


    -Brakes could have been replaced on axle 2 more recently due to a blown wheel seal.

    -Weight distribution on the drives during braking. ABS keeps wheels from locking. More weight transfer to an axle means it can brake harder without locking up.

    -Mix match of shoes between the 2 axles. Softer friction material will wear quicker.

    -Possibly a difference in cracking pressures of the drive axle relay valves. Cracking pressure is the amount of PSI from the pedal that is needed to overcome the spring in the relay valve.



    There is a bit of a misconception with slack adjusters. Yes everything modern is required to have auto slacks. They adjust the shoe to drum clearance and keep it constant. However, due to the design of the chambers, they produce the same amount of force per PSI of application through out their entire stroke.
     
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  6. AModelCat

    AModelCat Road Train Member

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    That's for certain types of hydraulic drum brakes. Hitting brakes in forward or reverse does nothing to adjust heavy truck drum brakes. The shoes are anchored solid on the brake spider. Adjustment is done solely in the slack adjuster. The auto slack wants to see a 90° slack to pushrod angle.
     
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  7. BoxCarKidd

    BoxCarKidd Road Train Member

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    Does your truck have piggy back, spring parking brake, chambers on both axles?
     
  8. Old Man

    Old Man Road Train Member

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    Do you ever go under your truck to inspect your brakes?
     
  9. drivingmissdaisy

    drivingmissdaisy Medium Load Member

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    This is perfectly normal. Internationals do this. Our company has 2019 and 2020 internationals and the 3rd axle drive brakes wear before the number 2 axles do on every International in our fleet.
     
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  10. Qbf594

    Qbf594 Medium Load Member

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    Southern Canadian annex, NY
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    I guess it depends on your definition of inspect. I get in under the 5th wheel plate and visually look at the brake shoes. That's what I initially saw and why I asked the mechanic to take a look. Because I don't know Jack about these. Every time I think I do I learn that I don't. That's why I'm here....
     
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  11. Qbf594

    Qbf594 Medium Load Member

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    Southern Canadian annex, NY
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    Original brake everything. I got this with 1342 miles. Now 106536 no repairs and 1 PM.

    Weight distribution makes sense except for I can't figure out how 2 and 3 could get very far apart since it comes thru the king pin /plate which is centered between the axles...
    I'll ask on the pressure adjustment when I get the shoes replaced.
     
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