Need Proper Adapter


New member
Local time
12:40 PM
Apr 18, 2020
Mesa, AZ
I am converting a Townie 7d with a BBSO2b and unfortunately the bottom bracket diameter is too big. Anyone know of a reasonably priced adapter?
I’ve not used them but only knew about them. According to the article, Bafang may require the crank be closest to the motor. See pic in middle of page.
Emailed with Luna today and their adapters are 3+mm too big. Back to the drawing board. Thanks again for your help!
Their OD is too big for my ID. I have some concentric adapters that fit perfectly, however they have a shoulder that sits outside the BB and makes the BB about 7mm too wide for the motor. Tomorrow I am going to cut off the shoulders and insert the adapters flush. The cross bolts will stop them from moving closer and the motor will keep them from moving outward. they are a very snug press fit. This, while not ideal, will definitely work. I only need them as spacers for the motor shaft. I have learned a very important lesson on BB's with this build that I will not soon forget. You can see the adapter HERE
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I hope this will be the final report on this issue. I took the bushings in the above post and, using my bench grinder, ground the collar down to the diameter of the bushing adding a slight taper to make certain that it would not hang up going in. This allowed me to insert the bushing until it was flush with the outside of the BB. I am happy to report that this worked exactly as I had hoped. I saved 7mm of space and the motor is now inserted and can be tightened down to spec. I will also install a high pressure hose clamp on the down tube above the motor that will have two very strong zip ties that go around the motor and through the clamp to prevent the motor from coming loose and dropping down. Burning Man will be much more fun for my wife next year next with the 17.5 AH battery and the added mileage she will get. I used this same kit for my Burning Man cruiser and enjoyed 80+ miles between charges using pedal assist. Chuy, I really appreciate your help and support on this project. If you're ever in the Phoenix metro area please look me up and I'll buy you a beer.
I‘m a bit surprised the Luna adapter would not work. It seems it was made for your style BB.

Is this the style you got?

If you are ever in San Diego area, I’ll buy you a beer. Tuesday evening is beer night with the boys, but any day of the week that ends in “Y” is good.
I would have thought so as well. Apparently the adapter is made for one specific bike. From their website, "Fits Niner Eccentric Bottom Bracket (EBB) bikes with a ~55mm ID." I thought it was odd until I realized it is for a popular tandem bike. I am really amazed, given the popularity of Electra Townies that a ready made bracket wasn't available. I did get the motor installed and it should be running early next week. I will post pics and comments then on a new thread.
We do get to the San Diego area on occasion for Burning Man events so I may take you up on that offer some day. Thanks again for your help and support.