Top Brake Shoe Closer To Drum Than Bottom

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by revzilla, Oct 18, 2023.

  1. revzilla

    revzilla Bobtail Member

    25
    14
    Jun 13, 2023
    0
    I was changing my brakes on a trailer I recently purchased and was wondering what could cause the top brake shoe to be at least 1/8" closer to the drum than the bottom?

    I've already checked these things:

    -S-cam Bushing Radial play is .025" (supposedly in spec, max was .032")
    -Flipped s cam 180 degrees and no difference so don't think cam is bent
    -New brake shoes are confirmed the right part number- but the top one does seem a little closer to the s-cam washer than the bottom (Not sure what I could do about that)
    -Drum was on tight
    -The old brake shoes I took off were worn evenly

    My brake shoe kit did come with oversize sleeves to fit on brake rollers- but don't think they were meant for my model or the side I'm needing it to go on. I wonder if out of desperation I could put one on the bottom brake shoe roller only?

    Any help appreciated, hoping the S-Cam housing isn't bent somehow. Or maybe I'm overthinking it and it's fine but it looks worse in person than in photos.
    IMG_8220.jpg IMG_8221.jpg IMG_8222.jpg IMG_8224.jpg IMG_8226.jpg
    IMG_8227.jpg IMG_8228.jpg
     
    Rideandrepair Thanks this.
  2. Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  3. Big Road Skateboard

    Big Road Skateboard Road Train Member

    5,684
    29,575
    May 2, 2021
    0
    Those are bushings, not oversize sleeves. In general though, wear on these parts, s cam bushings, cam, puts the shoe closer to the bottom, not the top.

    Check bearing play, and if it's good, run it
     
  4. revzilla

    revzilla Bobtail Member

    25
    14
    Jun 13, 2023
    0
    Bearing end play was in spec .003" lifting up with a crowbar on the wheel
     
  5. Big Road Skateboard

    Big Road Skateboard Road Train Member

    5,684
    29,575
    May 2, 2021
    0
    You may have some wear on the spider, causing the shoes to slightly sit at an angle. What year is this vehicle? I see you have std Q's instead of Q+
     
    Rideandrepair Thanks this.
  6. revzilla

    revzilla Bobtail Member

    25
    14
    Jun 13, 2023
    0
    It's a 1997 Wabash Flatbed
     
  7. Goodysnap

    Goodysnap Road Train Member

    3,694
    8,948
    Jul 12, 2017
    0
    I would start with installing the new bushings/sleeves in brake spiders for the anchors pins.

    Inspect the hubs for buildup or corrosion on the stand offs which can prevent square seating of the new drum on the hub. Put a few dabs of grease on the hub flange and tighten the lugs to ensure the drum is seated to the flange even all around.

    Does the drum stay the same distance from each shoe with a full rotation? Runout?

    Assemble everything and adjust. Make some firm brake applications and recheck.
     
  8. Rideandrepair

    Rideandrepair Road Train Member

    17,198
    55,777
    Aug 8, 2015
    0
    The bushings are for the bottom rollers. Yours are probably seized up and stationary. Sometimes they’ve been seized so long the shoe wears a groove into the roller. It’s very common. No one bothers to heat and beat the old ones out. Doesn’t hurt anything. Might make a brake squeal. Usually the cause. Those shoes look fine. They’ll wear in even in no time. Notice they’re tapered down at the ends. The spiders on my old Trailer aren’t perfect. Never damaged, just welded on at the factory a bit off. Make sure you got the springs on correctly. How can the drums be tight if you backed off the slack adjusters? Usually takes a sledge hammer to break them loose, then slide off easily. Maybe watch a couple YouTube videos. Not sure you’re checking end play properly. Should be by pushing in and pulling out on the hub assembly, not up and down. Timken websites is a good source of info. Merritor website is good also. Good info on brake shoe identification - Q VS. Q plus. The S cams are different, one has longer forks. I have to reference it every time I do a brake job. Like you, I worry too much. Better safe than sorry. As long as you have the right shoes, and springs on correctly, should be fine.
     
    elliott, Bud A. and revzilla Thank this.
  9. revzilla

    revzilla Bobtail Member

    25
    14
    Jun 13, 2023
    0
    Goodysnap- Yes the drum still stays closer to the top brake shoe visually even when hub is turned but haven't done a run out on it

    Rideandrepair- I just meant the brake drums had the lugnuts on them tight, the hub does turn fine

    I did end up putting a slide caliper on the brake shoes and the bottom brake shoe was more like .045" further away so difference was maybe not as bad as I had originally thought
     
  10. Rideandrepair

    Rideandrepair Road Train Member

    17,198
    55,777
    Aug 8, 2015
    0
    2EAE97E0-B77D-4E42-B93E-F6789CB79EAA.png 4FF835DD-2AFE-4353-AE13-71A09CDCB7A0.png I had 2 on my Trailer that were very obviously crooked. The shoes were pretty thin. I thought maybe bent spider or real bad S cam bushings. My bushings were a bit sloppy, probably needed replacing. I was surprised the new ones fit correctly inside the drums. The gap on yours looks like the brakes still need adjusting. Only back them off a half turn. Maybe only 1/4 turn if S Cams bushings are sloppy. You can check the push rod travel. Shoot for 1” on all of them. Once they’re adjusted good, it’ll be hard to see any gap at all. As long as they release and don’t hang up, good to go. They’re going to wear in along with the drum wearing too. Here’s the before and after.
     
    Bud A. Thanks this.
  11. MRMTRANS

    MRMTRANS Medium Load Member

    334
    372
    Apr 28, 2015
    0
    I've delt with the same issue. No big deal because brakes always wore well, except that one shoe had just a little less pad than the other when I replaced them. All of my brakes on each wheel assembly had a one shoe with a little more wear than the other, yet were was even on each shoe. I believe brake performance would be effected, even if just slightly. I am over cautious when it comes to safety stuff on a semi. I even change drums when putting on new brake shoes. What a pain that was to change those anchor pins. I wondered if they had never been changed in the 20 year life of the truck. I even have a tiger tool anchor pin press and couldn't push 2 pins out- and that included heat. I had to cut the center of the pins with a 4 1/2" angle grinder and diamond cutoff wheel, then push them out. I suppose acetylene would have worked, but I don't have. There was no doubt that the anchor pins and bushes were the problem after changing them. Just a little change in the anchor pins position causes a greater change in the brake pads. Now I always change pins when putting on new shoes. One other thing that might be your issue is the drum isn't centered because the hub pilot is off. TRU-BALANCE makes centering sleeves that you screw on the studs to center the drum and wheel, but they are only long enough to center one wheel. They aren't long enough to center the outside wheel too on a duel setup. They also make centering tools for the wheels only. You could center the outside wheel with them and sleeves. . I don't use the centering sleeves on duels-only steers. I use the wheel centering tools and tighten the brake brakes before torquing down the wheels.
     
  • Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.