How to order the right BBSxx kit the first time.
When starting out looking though forums and online websites it can be confusing. The are too many variables involved for Luna or the electric bike forums to give a definitive answer . The only way to know for sure if a customer has done an exact same build and posted in our forum here: or if its been posted elsewhere on the web.
This article is meant to help you go through the process in a way that increases the odds of you ordering the correct parts the first time and avoiding the costly shipping charges and delays when you get it wrong. It also should give you an overview of the initial ordering problems that you must take into consideration.
Let's get started.
Building a mid drive BBS bike is a job, for most of us a really really fun job ! Like any job, you have to start at the bottom. In this case the bottom bracket shell. Even if you know your bikes specifications inside and out, you cannot just skip this step. The cost of getting it wrong is too high. The first piece of information you need is what kind of bottom bracket you have. The answer to this question will determine if you can even install a BBSxx drive or not.
Start by measuring the width of the bottom bracket shell, from face to face. Do not measure any bearings or other pieces, you are looking for the bottom bracket shell width only. Measure it twice. 99.9% of you will have a measurement between 68mm and 120mm. If its not, then it is an install that is outside the scope of this article.
Remove the bottom bracket from the bottom bracket shell using the appropriate tools, this is a job for your local bike shop if you dont have the tools, patience or know how. Even if you do have the tools, some of them can be very stubborn to come out even if the bike is brand new.
If your bottom bracket shell has threads on the inside this is great news, it means your style of bottom bracket will likely take the BBS motor without needing an adaptor. Threaded bottom bracket shells are called JIS or BSA standard and this is what the Bafang motor kit was designed to work with. The inside diameter of your JIS-BSA shell should be 33.8mm +/- .2mm. Check it. Twice.
If your bottom bracket does NOT have threads , but has pressed in bearings, don't panic. Yet.
There are adaptors for some of the most common press fit style bottom brackets, not all but some. How to determine what kind of non-threaded BB you have and if you can get an adaptor or if you are out of luck.
So. At this point you have a bike with a bottom bracket shell between 68 and 120mm and it is a JIS-BSA type or you have put in an adaptor and made it one.
Here is the link to the BB adaptor for the press fit BB PF41