Free 173 Best Homemade Tools eBook:  
Get 500+ tool plans, full site access, and more.

User Tag List

Results 1 to 3 of 3

Thread: Semi trailer brake spider repair

  1. #1
    Supporting Member Frank S's Avatar
    Join Date
    Aug 2015
    Peacock TX
    Thanked 7,227 Times in 3,473 Posts

    Frank S's Tools

    Semi trailer brake spider repair

    on semi trailers there is what is termed as the spider this is what the brake shoes and the "S" cam actuator shaft mounts to Over time the bores can be come worn. On the show mount side it is best to ream these out and press in a sleeve the sleeves are often provided in new hardware kits However on the "S" cam side the bearing or bushing if you will is made of plastic and no sleeves are never provided in fact they are not even produced or sold. You choices for repairing these locations boils down to either welding them up and line boring them back to size. or line boring them to a larger size and machining your own sleeve to press in or you can rough grind them with a dermal stone and repair them with a metal empregnated high temp epoxy.
    obviously one of the line bore methods would be preferred but also the most expensive and time consuming. The epoxy method will usually last for years with the plastic bushings on the semis that have the bronze bushings line boring and repairing would be much better.
    Here's what I did I turned and ground a piece of tubing to a .020" undersize OD of compared with the new plastic bushing this was to allow for the finished bore of the repair to give the proper crush on the bushing
    Semi trailer brake spider repair-wp_20200826_10_31_45_probh.jpg
    I then used a Dremel stone in a drill to grind the ID of the locations leaving it rough and in the shape of the wear.
    Semi trailer brake spider repair-wp_20200826_13_05_43_probh.jpg
    Then after making a full set of arbors or sizing mandrels I wrapped them in plastic kitchen wrap this was to insure the epoxy could not fuse with the mandrels don't worry about a few wrinkles in the plastic wrap it is so thin they wont matter very much anyway.
    Semi trailer brake spider repair-wp_20200826_13_30_57_probh.jpg
    Next mix the epoxy fill the bore and inset the mandrel
    Semi trailer brake spider repair-wp_20200826_14_50_24_probh.jpg
    leave the mandrel in until the epoxy is fully set but not completely cured, the Epoxy I used said set in 6 to 10 minutes hard in 6 hours machinable in 24 hours
    I removed them after 20 minutes and was able to trim the excess with a sharp knife saving me a lot of grinding or sanding later

    500 Tool Plans
    Never try to tell me it can't be done
    When I have to paint I use KBS products

  2. The Following 3 Users Say Thank You to Frank S For This Useful Post:

    baja (Sep 3, 2020), desbromilow (Sep 3, 2020), sak778 (Sep 2, 2020)

  3. #2
    greenie's Avatar
    Join Date
    Dec 2018
    Thanked 73 Times in 40 Posts

    greenie's Tools
    Have to ask this question ------------- what will happen to the epoxy, once the heat starts to be generated from the brake shoes being applied ?

    I have seen brake drums glowing red, from overuse of the brake pedal by imbeciles at the steering wheel. All that heat is transferred to all place close to the brake drums and that S cam is surely very close to all this heat being generated.

    Even a cautious driver will make the wheel bearings very hot to touch after a long downhill run, so I can not see the epoxy lasting very long at all, then you'll have a bunch of very defective brakes on your trailer, when you are relying on them the most.

    Psst, -------------- hope you got GOOD health insurance.

    Homemade Tools eBooks

  4. The Following User Says Thank You to greenie For This Useful Post:

    bigtrev8xl (Sep 3, 2020)

  5. #3
    Unkle Fuzzy's Avatar
    Join Date
    Mar 2017
    Near Monkeytown, USA
    Thanked 86 Times in 50 Posts
    greenie...the factory bushings are plastic.

    Tube Bender Build Guide

  6. The Following User Says Thank You to Unkle Fuzzy For This Useful Post:

    Frank S (Sep 3, 2020)

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts