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Frustration with "73-100mm BB" BBSHD kit

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    Frustration with "73-100mm BB" BBSHD kit

    I just wanted to air my frustration with what LunaCycle markets as a "73-100mm BB" Kit.

    First, a bit of history. I'm building an ebike after getting a job closer to home and ultimately selling my car. I'd like to commute to work on a bike (12mi round trip), but don't want to have to pack clean clothes and then wait an hour to cool off to change into professional attire; an ebike is perfect for that. I made myself sell the car before ordering parts for the bike to ensure funding was available, so I'm without a personal vehicle at the moment. The platform I'm building on is a Surly ECR, which is currently outfitted with 29+ tires (3" wide). There isn't a lot of information about people turning this bike electric with BBSHD kits. The bike has a 73mm BB, but wide wheels, so I was afraid of interference with the chainstays. After all of the reading that I did here, and on Endless-Sphere, I thought it was best to get the larger BB Motor to ensure that I wasn't going to interfere with my chainstays. I made my order, and then it was time to wait.

    Well, the Friday after my order was made, I found a thread here with someone that built a Surly Ogre (same frame, narrow tires) who confirmed that they used the smaller BB BBSHD Kit (68-73mm). Crap. I called Luna to try and change the order, but it had already shipped. The service rep assured me that I would be able to make the motor fit with the provided spacers. Ok, fine.

    Yesterday the shipment came in. WOHHOOO!!! Time to build this thing up!

    Not so fast. The shaft that goes into the BB is WAY too long. There is no way in hell that this can fit without an inordinate amount of spacers (Definitely more thatn what is provided in the kit). How can LunaCycle market this as 73-100mm? I know that in the pictures I show half of the spacers on the non-drive side, and that the locking ring should be touching the bottom bracket, but the setup in the pictures is how I would want the drive side situated to ensure a good chain line. In the picture you can also see that the locking ring is in line with the motor mounts, so the only way to get the locking ring to touch the BB is to push the drive side out an additional 25mm. That would suck.

    I wanted this to work. I fiddled with this as much as I could last night until I realized that the best solution would be to return the unit for the 73mm BBSHD. I've got a new motor and a new battery on order (the battery I ordered was too big for the frame - totally my fault for not validating dimensions). I'll be shipping the original motor and battery back for a refund ASAP. I'm mostly frustrated with the waiting at this point. I don't think I'll see the shipment made until next week, and then it'll be another week until it arrives

    I'm seeing other users that have dealt with this by putting a steel tube between the lock ring and the BB. Is this what I should be doing instead of exchanging for a smaller unit?
    Hello all, First time eBuilder here starting to assemble a Motobecane 29er fatbike with a Bafang bbshd. Waited until the bike arrived before ordering the motor kit


      I have the 120mm drive in a frame with a 100mm bottom bracket. I had to use 20mm's worth of spacer rings, and it's working well so far.

      I'm sorry to hear about the difficulties you are experiencing, and I wish you the best of luck...
      Last edited by spinningmagnets; 08-12-2016, 11:56 AM. Reason: speling


      • Doc.neuman
        Doc.neuman commented
        Editing a comment
        The way I understand the 120mm drives is that the spacers end up being needed between the black locking ring, and the first locking nut. In my case, the spacers are needed between the black locking ring and the bottom bracket. I'm unsure if that's and acceptable installation as it pushes the left pedal out 1 in.

      Mine came with three spacer rings, but two of them were pretty thin. I ordered several of the fattest spacer rings Luna has, and I found a combination that worked. If you have one spacer, you could fit it in between the chainring side and the right edge of the BB shell to see if that would cause a problem. Then buy more spacers to space the drive in the center.

      Karl wrote on his blog that the drive needs to be firmly up against the BB, but he meant that if the large gear reduction housing was hitting the front of the right side chainstay, there would be airspace between the drive and BB. You can add spacers on the right side, you just can't leave any airspace, with the drive housing pressed up against the chainstay.
      Last edited by spinningmagnets; 08-12-2016, 02:06 PM. Reason: speling


        Actually it's not uncommon for buyers to use that much in spacers. Wanting a drive that will be able to be used again in another frame with a wider bottom bracket. It is done, I'm about to de the same thing.!

        Another vendor is coming out with a "torque arm" for the motor. It will solve the dlilemna when the pile of spacers allow motor drop. More a product suited to Pedicabs.


          Hang in there! You will get it right. Well worth the wait. On that bike you will not be disappointed.


            some frames are tough to get work and i gotta say Surly is among the toughest we have installed.

            its always better to be too big than too small.... on a surly fat bike you could get the 68-73 and then your bb not be big enough and then the only way to get it too fit is too grind down your bottom bracket which on an expensive frame like that does not seem the right answer.....


              Thanks for all the input!

              I ended up canceling the smaller BBSHD order. After much deliberation, I realized that in order to get even pedal spacing, the larger BBSHD unit would actually be easier to configure. With a smaller unit, I would need an offset crank arm on the left side.

              Anyway, I found a machine shop in town that made me a steel spacer to go between the black locking ring and the BB. I have all of the kit included spacers on the drive side, and a custom 11/16" long steel tube on the other. I'm a little bit worried about the friction fitting between the steel spacer and the BB, but I'll just check the motor weekly and re-torque if necessary.

              The one issue with this setup is that the chain line won't really allow me to use the 30T Mighty Mini. I'm going to go with the Luna Eclipse with it's large offset, and future expandability.

              Thanks again for all the help.


                I realize this thread is a year old but there are some similar questions now that this thread will help and maybe I can add a little info.

                First the disclaimer, All of these measurements used the "eyeball method". I got out a tape measure and I am giving my best estimate of these measurements without taking my bikes apart.

                The BBS02 is on a bike with a 66mm BB. Drive side, from the bb to the outside of the crank arm where the bolt is 2.5" On the left side it is 2". The diameter of the gear housing is 4.5".

                My BBSHD is the 100mm one but it is mounted on a 66mm BB. This really changes things because the drive side would be the same but the left is pushed out due to the extra length of the BB shaft.
                I shouldn't have done this but this time I made my measurements from the center line of the bike. So drive side, center to outside of the crank arm at the bolt is 3.75" and the left side is 4.5". The gearbox diameter is 5".

                The actual flats of the motor are offset to the left. 3.25" left of center and 1.5" right of center.

                I don't know how the left crank clears the motor on the left side of a 66mm BBSHD because there isn't much clearance on my 100mm BBSHD and it is 34mm wider.

                BTW I never thought of or noticed the offset until it was brought up in another thread.


                  I have been considering a Surly ECR or Soma Juice for my next 29er semi-plus (Surly Ertaterrestrials 29x2.5 that measure about 30" diameter and 2-5/8" wide on 39ID rims). Thank you for posting the photo of the chain stay clearance for the BBSHD. All those spacers to use a 100mm model seems a bit much to me. I think exchanging it for the proper 73mm model would be best, but...

                  Do you or others know if the BBSHD has a larger reduction gear housing than the BBS02? Someone put a BBS02 on a Surly ECR with a Rohloff and posted here. I don't remember there being any chain stay clearance issues.

                  Do you know if the Surly Orge can actually fit Surly Extraterrestrials? I'm leaning towards the Soma Juice, because I had such good luck with my Soma B-Side build. The new B-Side and Juice have 73mm BB's, while my 2016 B-SIde V.2 Belt Drive only had a 68mm. My thought was to face the right side of the BB down on a 73mm Soma Juice 5mm giving an offset 68mm BB. If the chain stay doesn't hit the reduction gear housing (it doesn't on my B-Side), then this will serve two functions. It corrects some of the BBS## pedals not being centered and it would give a better chain line.

                  Anyway, just bouncing some thoughts around and hope someone can answer my questions. Looking forward to seeing your ECR finished. I hear they are very nice riding bikes that you sit down in, not on top of.
                  MOVING BACK TO PEDAL...
                  2020 Banshee Paradox V3 1x11 (pedal)
                  2018 Soma Wolverine 3spd IGH Belt Drive (pedal)


                  • Burkebiker
                    Burkebiker commented
                    Editing a comment
                    The HD does have a bigger reduction gear, by about .25 inch at the point it begins to taper from the center of the BB.

                    I just bought an ECR 29+ and installed a BBS02 because I had one that I had just taken off another bike. It barely fit, as in if I had any less thread for the BB nut I wouldn’t feel comfortable. For chain stay clearance I had the use a spacer that is
                    about 4 mm and I had to use a left side crank arm with offset. A Lekkie 42t Bling Ring was used for better chain alignment.

                    I have another bike with a BBSHD for a 100mm BB and if I have time one day, maybe I’ll remove it and try it on the ECR, but the BBS02 really performs well and is suited for my needs. Photos to follow.



                  • Rider
                    Rider commented
                    Editing a comment
                    That's beautiful! Thank you for posting it. What exact crank arm did you use on the left side and where did you get it?

                    I've got two BBS02B motors now and both are off their original build frames (Soma B-Side and Electra Lux Cruiser). The Soma B-side is in the process of getting reworked with different forks, tires and belt drive 3spd gearing. The other motor is looking for a frame like the Surly ECR that fits my Velocity Dually wheels with Sturmey-Archer 5spd IGH and Surly Extraterrestrial 29x2.5 tires. I got to sell something before I buy a new frame though...

                  I got the crank arms on eBay- they're Shimano STePS arms and cost the same as the Bafang arms, but are much better quality. Luna had been out of stock of the offset arms for a while it seems.


                  • Poco Askew
                    Poco Askew commented
                    Editing a comment
                    Any idea how much offset they provide?

                  • calfee20
                    calfee20 commented
                    Editing a comment
                    I have a couple of sets of steps. I will go in the barn and take a photo but I believe they are straight.
                    Last edited by calfee20; 12-05-2017, 01:38 PM.

                  So how do you measure offset. Maybe a photo.

                  Click image for larger version

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                  Left to right--------- Bafang, Shimano, Electra Cruiser

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                  I bought mine here.


                    Originally posted by calfee20 View Post
                    So how do you measure offset. Maybe a photo.
                    I bought mine here.
                    Good question! ;)
                    I think your photos did the job. Thanks for digging them out and taking the pic's.


                      Those crank pictures are a big help. It looks like the bafang cranks have more offset than the shimano steps. If so, that could help my situation. My pedals are about 12 mm farther out on the right (drive side) than the left. I'd like them to be evenly spaced from the bike's centerline. Instead of getting more offset on the left, I'd like to decrease offset on the right. I'm thinking I should use the shimano crank on the right and keep bafang crank on the left. Advice? Has anyone done this?


                      • calfee20
                        calfee20 commented
                        Editing a comment
                        I was answering the question of how much offset the steps had. The last photo was not setup correctly to show offset. I was just showing a profile view which may be distorted. Give me a bit and I will take two more photos with the square so there will be a better comparison.