More and more customers have been asking about the feasibility of using a Bafang mid drive on their belt drive bike lately. So I have been doing a lot of research on this topic and will present my findings in the post. First let me point out that I am not a bike expert and since there are so many brands and models of bikes out there, you will need to do some research on your own to insure the best possible outcome to converting your bike. With that said let’s get into it.
The chart below is based on the Gates Carbon Drive belt system
Since Gates seems to be the only viable game in town, they are naturally the system we will be talking about. Also, in order to use the Gates drive pulleys, you will need chain ring adapters to be the interface from the Bafang to the Gates bolt on pulleys. I have chosen the California Ebike BA104, BA130 (used on BBS01/02/03) and the HD130 (used on the BBSHD 68mm and 100mm bottom brackets) adapters to calculate offset compatibility. There are other factors that you will need to consider and I will go into that further down in this post.
Why not just build “Special” offset pulleys?
We wanted to build special offset pulleys to help accommodate more brands but Gates Rubber has patented their pulley geometry and will not allow 3rd parties to produce pulleys. They also will not make specials according to their engineering department. So, in our opinion, Rohloff is probably the only consideration for a successful belt drive system. We had hoped to find a solution for the Nuvinci but at 12.2mm and 14.2mm offset misalignment, we felt there is no way at this time to make them work.
What else is there to consider?
I will list here some of the more obvious things to look at.
Many customers wanted to use the beautifully engineered Tout Terrain belt drive bike. The Bafang can’t be fitted to this type of bottom bracket.
See the above. Gates ask you to check if your sprocket will clear the chainstay once mounted? Before you make that determination see how your Bafang mid drive will fit up.
The above is a ruff sketch of the BBS01/02/03 mid drive assembly areas for consideration. Will the final gear housing (113mm diameter) stay clear of the chainstay when mounted up against the 68mm bottom bracket?
Or on the BBSHD. Answer the same question but now the housing is 132mm diameter.
We will add more content to this subject as it becomes available but we felt that our customers should know what to look for when considering a belt drive system. Belt drives are fantastic when mounted with proper alignment but marrying a Bafang mid drive to the belt drive bike is a challenge unless you do your homework.
I would love to hear from those of you who are able to make successful installations. Tell us the make and model bike that you use and send some photos.