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Non-Concentric Brake Drums

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  • Non-Concentric Brake Drums

    The chain on my knucklehead has what the service manuals always described as a 'tight' spot and a corresponding 'loose' spot. As anyone with and any sense knows, the link distances in newly manufactured chains is both accurate and consistent. These 'tight' and 'loose' spots are the result of the chain sprocket running eccentrically to the brake drum lug pattern in the wheel hub. In pronounced situations, this can affect the machine's braking ability and on this this particular drum the eccentricity is quite pronounced. In fact, The drum is so eccentric that I can't get the shoes centralized such that both are in contact with the drum when the brake is applied. This lead to some 'interesting' traffic stops, especially then the one operating shoe gets a little hot. Not good at all. After identifying the problem as the (OEM) drum only, I replaced it with a new, popular aftermarket drum. Same problem, but not as pronounced.

    With the later cast iron drums, the drum could be cut thereby limiting the eccentricity to the sprocket only and not the shoe-to-drum radius. However, one must be careful when cutting the earlier, thinner mechanical drums.

    My questions is how do you (or even CAN you) get the brake shoes to equally purchase against the brake drum given this condition? Also, with Hebron approaching, I'm thinking of purchasing one of V-Twin's complete Backing Plate/Drum assemblies for temporary use hoping that as an assembly it would run true. But, but I'm a little skeptical - especially when it comes to stopping these old bones!. Before I spend the money I must ask; Has anyone had experience with V-Twin P/N 23-0876??
    Bill Pedalino
    Huntington, New York
    AMCA 6755

  • #2
    I would try another original drum, usually easily found. Many of the old drums have been bumped and have a low spot, but it sounds like yours is really bad.

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    • #3
      Don't know if this relevant, I have a 36 Packard that we just rebuilt the brakes on. The wheel hub showed some wear so I took it to a friend that does old cars. He measured and came up with 60Thousands wear. He mounted the shoes in a machine that cut the new lining to account for the wear. The brakes work good and according to him this was done all the time Pre WWII
      Hope this helps
      W

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      • #4
        WIll - the process your speaking of is 'arcing' the shoes to the radius and diameter of the drum. I do this on every brake installation. Thanks for the suggestion though...
        Bill Pedalino
        Huntington, New York
        AMCA 6755

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        • #5
          Well Folks,

          I just walked an associate through a very, VERY trying episode attempting to get an off-set springer front brake to hold even at a stop.

          The V-TWIN shoes and linings got carefully and tediously carved down to splinters with zero improvement at all.

          If I hadn't touched them myself, I wouldn't dismiss them as a complete, total liability, and junk. But they are worse, if that is possible.

          Seriously.

          ....Cotten
          Last edited by T. Cotten; 07-29-2016, 03:38 PM.
          AMCA #776
          Dumpster Diver's Motto: Seek,... and Ye Shall Find!

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