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How to Order the Right BBSxx Kit !

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    How to Order the Right BBSxx Kit !

    How to order the right Bafang BBS02 or BBSHD the First Time !

    Many folks ask the question "Will a BBSHD fit my (insert any bike here)?" . The simple answer is usually "Who knows?" . There are too many variables involved for Luna or the electric-bike forum users to give a definitive answer. The only time someone knows for sure is if they have done the exact same build or there is a identical build posted in the Customer Gallery .

    Building an ebike using an existing bike and adding a kit like the Bafang BBS series of mid drives is an engineering puzzle that each builder must solve for themselves. Fortunately there is a lot of help and information available to make it go smoothly, even if it's your first build. The issues arise when people are excited about starting a new bike build and rush into the process without doing their homework first. These are not one size fits all and some due diligence on the builders part is mandatory for a sucessful outcome.

    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 concideration.

    I'm not going to get into the specifics of unscrewing a pedal, research anything you are not sure of. I will however point out anything important.
    For a more detailed description of the dissassembly process I recommend this article.

    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.
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    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.

    *Sometimes manufacturers use the term "sealed cartridge" in their stated bottom bracket specs. Typically this means it is a standard BSA bottom bracket and should be fine, although ideally we would recommend physically measuring and confirming first.

    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. There is an article discussing adaptors and press fit bottom brackets here, 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.

    End of step one. Congratulations.
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    Next thing you need to do is determine which size (length) motor kit you should order. The following compatibility chart shows where you should START , do not skip ahead and order yet !

    Read across the chart where it says "Your BB Width" and find the column that your measurment belongs in. Read down that column to the line for JIS/BSA. That will tell you what motors you can use. The top line will tell you what size kit you are going to START with.

    For example: A BB width of 90 mm can only use a BBSHD and you would start with a 100mm BBSHD Kit.

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    It is worth noting that on the BBSHD you can go a couple MM over the specified width (i.e. use a 100mm motor with a 102mm BB shell) You would just use only the first lockring and use loctite on the threads. (just like when using the 68mm bbs02 with a 73mm BB shell)

    End of step two, you are almost there !

    Why don't I just order that kit now?
    Excellent question!
    The reason is every bike has a little bit different shape to the chainstays and it is important to make sure that motor can sit flush up against the BB shell without the gear housing hitting the chainstays.

    A regular bicycle BB ends at the face of the BB shell. The BBS motor kit has a large gear housing on the drive side. As you slide the motor into the BB shell the gear housing can hit the chainstay BEFORE the motor is completely seated against the BB shell. In the photo below of my bike you can see that I had exactly that problem and I needed to add spacers to the motor shaft to move the gear housing out enough to clear the chainstays. This is why the chart is only the starting point for choosing your motor size. BB spacers are part of a normal install.
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    OK, take a deep breath and relax.

    Here is where you need to apply some common sense to save yourself some time and some money.

    If your chainstays flare out sharply from the back of the bottom bracket then you are likely to have this problem. If your bike has a narrow BB shell (like the one in the photo 68mm) but has fat tires, then the chainstays are going to have to flare out to make room.
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    *For an in-depth article on intrusive chainstays please visit this link
    Go online, search the forums at and Google BBSHD installs, look at other peoples builds look at their chainstays, look at the links at the end of this article, look at everything you can find, and then look at your build. If there is any doubt that you might not have enough room, get the next size up.

    The only downside is you will have a little bit wider Q factor (distance between pedals), that's it.

    The upside is, a few mm of increased Q factor is not a big deal. Your kit will fit a lot more frames if you want to move it in the future. You avoid the delays and cost of returning it and paying shipping, both ways, on the return.

    Deciding between BBSHD or BBS02

    If the bike will have a heavy load, (i.e. towing something or heavy rider weight) then you want to pick the BBSHD over the BBS02
    (the HD stands for Heavy-Duty)

    Technical extras

    This picture can help you figure out if the BBSHD will clear your chain stay:
    TO BE Really accurate, it's actually 62mm after proper measuring
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    The BBSxx only has about 12mm between the motor casing and the spindle so this needs to be taken into account when making measurements.

    Below left photo is an example of a press fit bottom bracket and with an adapter for the pf41 this only leaves 6mms for the frame thickness.

    Mid drive pressfit bottom bracket documentationClick image for larger version  Name:	image_7686.png Views:	1 Size:	177.7 KB ID:	46921

    If you just need to add 4mm of spacer on one side you can probably get away with using the 68mm-73mm version, especially if it's a 68mm BB. It'll work up to ~77mm if you do without the black lockring and use loctite instead since the black lockring is just a jam nut, it just keeps the other nut from loosening.

    Do not add spacers to both sides, that's not usually how it's done. Adding spacers on the left causes a tendency for the motor to twist unless you do some extra mods. If you want a spacer on the left just due to a concern about pedal or crank offset I'd just get an offset lefthand crank instead.

    Check out the BBSHD manual here.

    Spindle length
    The 68mm units spindle is 88mm this includes 20mm of thread
    This also applies to the 100 and 120mm units, the spindle length for either of these units plus an additional 20ml of thread

    Obstructions in Bottom Bracket shell
    While relatively rare, it is possible for the inside of the shell to have a bit of material that may need sanded down to push the axle through. This may be due to how the shell was welded on, etc. Sanding it down can be done with a Dremel, sandpaper or a file easily.

    Here are some useful links to other discussions about fitting a BBSxx and getting the right size kit.

    Knowledge base thread on press-fit BB, eccentric BB and carbon frames

    BBSxx knowledge base master repository

    Electric-bike article on installing a BBSHD

    Karl's excellent article about adjusting for chainstay clearances

    Considerations for mounting 100mm motors in 73mm frames

    Best practices for spacing out BBSHD

    Endless-Sphere Non-Hub Motor Drives

    BBSHD and BBS02 Wiki

    If you are not sure which chainring to get keep in mind that it comes with a stock chainring, you can always start with stock and upgrade to something else later.

    Step by step how to pick out a BBSHD kit for your build
    Last edited by paxtana; 02-08-2019, 03:58 PM.