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Bottom Bracket Adaptors (BB30 PF30 PF41)

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    Bottom Bracket Adaptors (BB30 PF30 PF41)

    BB30 PF30 PF41 Press Fit Bottom Brackets and Bafang Mid-Drive Kits

    If you are planning to build a mid-drive BBSxx series bike, then the first piece of information you need is what size and type bottom bracket shell you have.

    Full article on choosing a BBSxx kit here

    The Bafang BBSxx series of motors is designed to replace standard JIS-BSA threaded bottom brackets. If your bike does not have that style you might still be able to install one using an adaptor. Basically an adaptor takes the (larger diameter) bottom bracket shell and converts it to JIS-BSA.

    What bottom bracket do I have ?
    Well, let's find out.

    Using the correct tools , remove the existing botton bracket. This job might be left to a local bike shop if you do not have the tools, patience or know how to do it yourself. Some bottom brackets can be very stubborn to remove, even if the bike is brand new.

    What you are looking for is the width of the BB shell and the inside diameter of the shell.
    Click image for larger version

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    Now that you have those measurements you can determine what BB style you have.

    The three styles that adaptors are available for are :
    This standard was designed to allow a larger crank spindle diameter so to add that space the bottom bracket shell was enlarged to a 42mm diameter.
    PF30 (see special notes below)
    This was intended to further strengthen the BB30 standard so set the BB30 bearings into a press fit cup, to add that space the bottom bracket shell was enlarged again to a 46mm diameter.
    This is much like a PF30, it uses bearing cups , but PF41 uses standard bottom bracket bearings instead of BB30 sized bearings. The result is a bottom braket shell that is 41mm in diameter.

    Special note on PF30** Huge thanks to @Sebz for the following important info I originally omitted**

    The outside diameter of the spindle on a BBSxx is about 33.6mm in order to fit through a JIS-BSA BB shell. The PF30 is 46mm. That means that the adaptor is about 6mm thick, to that you need to add the thickness of your BB shell. If your shell is 5mm thick then you have used 11 mm from the edge of the "hole" to the outside of your BB. The BBSxx only has about 12mm between the motor casing and the spindle so this will be a VERY tight fit with little room for error or sloppy measurements. Measure twice, then have someone else measure twice or you may be in for some unwanted fabrication aggravation!

    It would be a very good idea to do this calculation for ANY size adaptor you plan to use, a little math can save you major problems.

    Click image for larger version

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    Not all of these standards come in all width bottom brackets. The fact that these three all have different diameters make it easy to determine what you have. The addition of the width will further confirm if you got it right. Look at the following chart for extra help.
    Click image for larger version

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    The manufacturers of these adaptors is FSA (Full Speed Ahead) a well known established manufacturer of bicycle components. Other vendors offer these as "custom machined" parts. I'm guessing that means sombody with a lathe in their garage making them to order at a premium "custom manufactured" price. Buy from the established manufacturers if at all possible. The BB30 and PF30 can be ordered from QBP by almost any local bike shop. The PF41 I have only seen on AliExpress. I don't normally encourage buys from that source but in this case I would rather buy from overseas and get a FSA manufactured part.

    From left to right:
    BB30 to BSA , PF30 to BSA, PF41* to BSA (*shown with bearing installed)
    Click image for larger version

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    Attached Files
    Last edited by LunaKB; 07-08-2016, 05:50 AM.

    This article was originally written by : @Bicycle365
    Contributing authors: @Sebz


      fantastic information


        Is there an installation guide (how to do it) for the PF-41?


        • intramorph
          intramorph commented
          Editing a comment
          The PF41 adapters get installed by a bottom bracket press fit tool. Some people make their own version out of a rod and some washers and nuts
          but the proper way is to use a press.

        En AliExpress conocéis de algun enlace de compra pf41 a Bsa?