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Bbshd fat bike problems

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    Bbshd fat bike problems

    I have a problem that some bright person hopefully can help me with. Im trying to convert a 100mm bb fatbike with a 120mm bbshd middrive. The chainstay is forcing me to use the 120mm version. But the distance between the motor mounting plate holes is 15mm from where the mounting plate will be placed. Is placing 15mm of washers a bad id? I'm concerned the motor might break the construction since it will be weaker than intended. Has anybody done this?
    grinding down the bb is not an option because of the chainstay.
    Does anyone sell offset mounting plates?Click image for larger version

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    I'd look for an appropriate sized spacer instead of stack of washers (that's just me and mcmaster carr is my friend) - but in all reality there's not likely a lot of lateral force on those mounts

    Not sure how you shimmed the other side but others have also used spacers that are in that realm of spacing


      This is the idea, but they might not be long enough.
      Click image for larger version

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        waste of time
        Last edited by stts; 03-24-2023, 04:45 PM.


          Sounds good that it's not alot of lateral force on the screws. I found a lekkie motor spacer that might help but I will have to move the brake cable then.
          5mm drive plate spacer for Bafang conversions. Is this compatible with your build? DOWNLOAD THE USER GUIDE here.  

          Might just try to find spacers for the screws.


            You might grab a torque arm kit. They're not too expensive. I flipped mine over and ran it up to the seat tube. The hose clamp section can be bent for some offset.
            I made a thread on this with a couple ideas for mounting the bolted end. I'm not a big fan of the hose clamp method. More metal in the seat post than the chain stay.

            For the gap in your photo Instead of washers or tubing spacers I would use these.

            Put it onto the motor over a metric set screw (so you can get it back out later), and bolt the outer end normally..

            You can use a short bolt and jam nut so you can get it tight on the motor.

            Another option would be a stud or threaded rod all the way through, with an acorn nut on the outside.
            McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

            Last edited by Retrorockit; 10-21-2022, 06:59 AM.


              That doesn't look excessive for spacers to me.

              Looks like this person is in Sweden, not sure what they have for hardware stores.

              Bigger question is what did you use for spacers on the other side and if there is more than a couple mm's what are you going to end up with for a chain line? If the chain stay was hitting the gear case its also likely gonna hit an offset chain ring so more spacers which kicks the line out further. Some fat bikes do seem to kick the cassette out pretty far so it may be ok but many seem to try and keep it tight in so end up not working well with a mid drive.


              • Retrorockit
                Retrorockit commented
                Editing a comment
                But metric should be normal there.

                That's just how I hang things. Even the cup holders on my bike are hung that way. Bolted through threaded spacers.
                Last edited by Retrorockit; 10-21-2022, 06:46 AM.

              Thanks for the replies! Yes I will have to space it out on the drive side. It will kick the chain line out about 15mm with the stock chainring. So I might not be able to use half of the gears. I might rearrange the gears on the cassette if I feel that i have a need for the higher gears (it's a 12 speed eagle cassette). If I get the Luna eclipse 42t it will only be 9mm off. So maybe that's an option.

              Yes I'm in Sweden but I think I can find something similar to what you linked to.

              I will have a look if the torque arm is necessary. Has anybody done a bbshd install with this kind of offset without a torque arm?


              • AZguy
                AZguy commented
                Editing a comment
                Pretty sure that, by far, most installations do *not* have the torque arm... as long as the nut is tightened enough should be necessary.. >12,500km very hard miles on my BBSHD build without one...

              The torque arm is optional but gives a more secure base for your spacers. The toothed plate will chew into the frame over time. I suppose the arm will be scarce in Sweden.
              You can enter your tire size and gearing here.

              In gear units 90rpm @ KPH is normal. This will give some idea of your speed when pedaling. But 140prm is available when throttling so look at that also.
              The BBSHD doesn't need a lot of gears. Maybe look at the top 2 minus every odd gear from there down? That would leave 7 wide gears.