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.
.
OK,
Now that you have those measurements you can determine what BB style you have.
The three styles that adaptors are available for are :
BB30
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.
PF41
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 CARBON FRAME BIKES, ECCENTRIC BB and all the bikes that uses a bottom bracket adaptor** 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. For Example the PF30 outside diameter is 46mm. That means that the adaptor is about 6mm thick, to that you need to add the thickness of your BB shell (frame). If your shell is 5mm thick (most carbon frames are more) 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.
.
.
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.
.
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 somebody 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.
Luna locking PF41 adapter (discontinued)
Luna custom cut adapter for 41mm ID BB
From left to right:
BB30 to BSA , PF30 to BSA, PF41* to BSA (*shown with bearing installed)
More Resources:
Here is a similar article on Endless Sphere discussing Bottom Bracket options and adapters
https://endless-sphere.com/forums/vi...p?f=28&t=80319
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.
.
OK,
Now that you have those measurements you can determine what BB style you have.
The three styles that adaptors are available for are :
BB30
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.
PF41
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 CARBON FRAME BIKES, ECCENTRIC BB and all the bikes that uses a bottom bracket adaptor** 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. For Example the PF30 outside diameter is 46mm. That means that the adaptor is about 6mm thick, to that you need to add the thickness of your BB shell (frame). If your shell is 5mm thick (most carbon frames are more) 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.
.
.
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.
.
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 somebody 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.
- For the PF41 / BB86 / BB92 we sell an adapter workable with any width
- We aslo have a custom 41mm adapter that can be cut to any other length
- For BB30 this is probably one of the easiest to work with
- For PF30 this will probably work
- Eccentric bottom brackets, this will work
Luna locking PF41 adapter (discontinued)
Luna custom cut adapter for 41mm ID BB
From left to right:
BB30 to BSA , PF30 to BSA, PF41* to BSA (*shown with bearing installed)
More Resources:
Here is a similar article on Endless Sphere discussing Bottom Bracket options and adapters
https://endless-sphere.com/forums/vi...p?f=28&t=80319
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