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    Loose BBSHD

    Hi, I had help building my bike and as soon as it was done, did a short ride and the motor was loose. We took off the crank and tightened up the shims and it was good to go. I left for Baja the next day, after only putting about two miles on my bike, without the Allen wrench and gear puller but with the wrench. And, you guessed it, my motor is loose again and I am in a remote village in Baja. So, first I used a plastic bread tie as a shim and the worked for a while shoved between the motor and bottom bracket, now I have a webbing strap holding it up as well. In about a week we will go to a town with a bike shop and I should be able to get the crank off and tighten it again, but does anyone know what I can do for a more permanent cure?

    #2
    1. Make sure the motor is tight against the frame when you torque the BB, so it can't rotate further any under motor torque.
      1. Inspect your frame where the motor contacts the bottom of the downtube. It isn't dented or worn there, is it/.
        1. You can optionally put a chunk of epoxy putty where they contact, to prevent the motor damaging the frame. Spreads the load. I tried rubber here, but the epoxy seems better. Alan B suggestion I think...
    2. Ideally, the steel Bafang motor bracket is against your bottom bracket with the little teeth inboard, biting the bottom bracket.
      1. Any spacers should be outboard of that Bafang bracket, under the nut.
    3. Make sure this bracket is also parallel to the BB flange. Adjust spacers if needed.
    4. Make sure drive side of motor contacts BB flange, not frame rear triangle. Add spacers if needed.
    5. Tighten the heck out of it. Really tight. I stand on the wrench, so maybe 150 ft-lb. Over spec.
    6. Blue locktite on the first nut. On oil-free clean threads.


    That should do it. Good luck out there!
    Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

    Comment


      #3
      I feel you pain. Mine also coming loose after a few kilometers of each ride after tightening. I have concluded that the flimsy Luna tool is not adequate. I think I have it as tight as I can with that tool as the tool is bending! I am waiting on the proper installation tool from Luna that works with a torque wrench.

      As mitigation to stop it banging on the frame, I have zip tied a brake pad to spread the load. Works well, but the motor still moves a bit, making a creaking noise. Not sure if this is practical in the field.

      1. Tighten the heck out of it. Really tight. I stand on the wrench, so maybe 150 ft-lb. Over spec.
      So it's not possible to strip the thread? I am concerned.

      1. Blue locktite on the first nut. On oil-free clean threads.
      I tried this, but I don't think it was tight enough and then really struggled to break the lock with the flimsy tool to tighten it further. Urgghh! Eventually backed it off a bit re-tightened.

      Conclusion - no substitute for the right tool in the first place.

      One question in my mind (and probably yours) is whether riding with the motor a bit (or a lot) loose will do any damage, assuming it is not bumping into the frame. It certainly takes a lot of smoothness out of the ride but the motor works fine.

      Comment


        #4
        When my BBSHD loosened while away from tools I used a bungee cord stretched really tight to secure the motor and it worked great.
        So great I forgot to tighten the nuts for a few days, and then I left the bungee cord on for a few more weeks as insurance.
        I was able to wrap bungee around downtube and then under motor and hook where kickstand normally would mount.
        This was probably a month or so back; yesterday I removed nuts to better align the motor mount bracket with spacers and it was tight as can be still.
        I am using that huge socket to tighten with though, and like JP said - really tighten it.

        The one thing you don't want to do is ride while the motor is jerking on every start, etc. as this will chew up your bottom bracket and or the retaining nut cover.

        Comment


          #5
          Okay ... I fixed it for good. What it needed was just one more spacer on the bottom bracket and now it is rock solid after 400 miles on that fix. I had to wait until I was able t get a crank puller, remove it, add another spacer from an additional spacer kit I got from Luna.

          Comment


            #6
            Originally posted by Raven View Post
            Okay ... I fixed it for good. What it needed was just one more spacer on the bottom bracket and now it is rock solid after 400 miles on that fix. I had to wait until I was able t get a crank puller, remove it, add another spacer from an additional spacer kit I got from Luna.
            Great! Thanks for the follow up.
            Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

            Comment


              #7
              I have two bikes and on the other bike i have no room for the black lock ring. So it should be torgued to 50~nm, but can i torque it even tighter without damaging the motors threads? I'm using loctite also.

              Comment

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