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Bottom Bracket Standards and Bafang mid drive motors

Will the BBSxx fit in my bike? This is a question that many of us need help in answering. The question you should be asking first is "what kind of bottom bracket does my bike have"? You need to know the answer to this in order to understand how the BBS02 or BBSHD will fit in your bike and what size motor to choose. Next you need to know that Bafang BBSxx motors have a bottom bracket shaft diameter of 33.5 mm and are designed to fit into the bicycle bottom bracket standard known as JIS or Japanese Industrial Standard, which is very similar to our standard here in the US commonly referred to as "square tapered spindle", ISO/English, BSA, British, or "threaded". Available in 4 widths, (68 mm)(73 mm Oversize)(83 mm Some Downhill & FR bikes)(100 mm "Fat bikes"). Shell inside diameter is 33.6-33.9 mm. BSA has threads on the inside of the shell measuring 1.37 in x 24 TPI. Below is an example picture of the BSA threaded Bottom Bracket easily identified with the threads on the inside of the shell. This is what the BBSxx motors were designed to fit into. So if your bike has a threaded shell like the photo below, you are in luck, now all you need to do is order a motor in the correct width.


BSA english threaded bottom bracket 

Fortunately Bafang makes the BBS02 and BBSHD motors in a variety of widths to fit several JIS and BSA bottom bracket shells with the proper knowledge. The BBS02 comes in one size only (68mm) unless you have a custom machined unit with a longer square tapered spindle other than a 68mm. The 68mm BBS02 and BBSHD can easily fit 73mm bottom brackets. All that is needed is longer fixing plate bolts and a 5mm spacer (or stack some M6 washers) to compensate for the 5mm difference between the fixing plate and the motor. Usually only the 4 notch M33 lock ring will  fit on the remaining spindle shaft threads and the second outer lock ring may not fit. What this all means is this... a 68 mm BBS02 can easily fit in both 68 mm and 73 mm shells. Bafang now makes the newer BBSHD model available in a variety of sizes (6 to be exact) : 68, 73, 92, 100, 110, and 120 mm. The most common sizes ordered by vendors is 68mm, 100mm, and 120mm since these can fit in all the other sizes and reduces inventory. Bafang produces more of these common sizes and lead time for the others can be quite long.

Unfortunately, bikes comes with a multitude (6+ other standards) of varying widths and diameters, none of which have threaded shells, but instead use press in sealed bearing cartridges, which means you may not be able to install the BBSXX motor into these bikes, so please pay attention. You may have one of these bikes or plan on buying one and don't even know it, thinking all you need to know is the width of your bottom bracket and order a motor between 73-100 mm and you are all set, sorry, this couldn't be further from the truth. DON'T BUY ANYTHING until you know exactly what kind of bottom bracket shell the bike has. I have dozens and dozens of emails from people who accidentally spent thousands of dollars on a bike only to find out the motor won't fit. They just assumed it would fit because the shell width was between 73-100mm, but they did not look at the shell type, or shell diameter, and the project comes to a screeching halt. Proceed with caution and try to make an educated build done right the first time.

There are several standards you need to be aware of that have larger diameter bottom bracket shells. It boils down to this, all the other standards (besides JIS and BSA) have larger diameter bottom bracket shells. The newer shell standards do not have threads in them at all and rely on press fit bearings being pressed in, instead of threaded in. They are notorious for having a "creaky" sound for this reason. Many bike manufacturers began adopting new standards around the 2012 time frame, some a little before, some a little after. What this means for you is, be especially careful when selecting a bike 2012 and newer because the chances of having a non BSA/JIS bottom bracket shell increases. The vast majority of older bikes pre-2012 have the appropriate threaded JIS and BSA style bottom bracket shells that the BBSxx motors were designed for and are usually a safe bet. Below are the standards to be aware of.

BB30: This was introduced as a new international standard utilizing a new, larger-diameter crank spindle and bottom bracket shell. With BB30, 42mm bearings press into the frame against inner snap rings. This is an open standard, like ISIS, that was originally introduced by Cannondale and has been adopted by crank manufacturers FSA, SRAM, and Zipp. If your bike has a BB30 bottom bracket, no worries, just get a BB30 to BSA adapter and the Bafang BBS02 or BBSHD will fit beautifully. Make sure to buy either a 68mm or 73mm BBSxx because BB30 is only made in these two widths. BB30 = good : ) 

BB30 bottom bracket drawing

Press Fit 30: Also called PF30, this is a variant of the BB30 design. The PF30 design uses BB30 sized bearings pre-installed in bearing cups. The bearing and cup are pressed into the bottom bracket shell. Because PF30 uses the same size bearings as a BB30, the cup material increases the bottom bracket shell to 46mm diameter. The PF30 system uses the same diameter spindle as BB30 and can be used with BB30 cranks. This is all wonderful you say, but... how do I get the motor to fit? Get a PF30 to BSA adapter and you are all set. This standard comes in 68mm or 73mm widths so choose your BBSxx motor accordingly. PF30 = good : ) PF30 and BB30 are the only press fit standards I know of that will fit the BBSxx motors with commercially available adaptors. 

PressFit 30 bottom bracket shell

The below mentioned do not fit the BBSxx motors. 

PF41/BB86/BB92: This standard was originally introduced by Shimano as an internal bottom bracket standard and has since been adopted by other manufacturers as Press Fit 41, or PF41. Some fat bikes use this standard, including the Salsa Beargrease and Surly Ice Cream Truck, which use a PF41 bottom bracket in different shell widths (121mm for Salsa and 132mm for Surly). The bearing cups are pressed into the bottom bracket shell, and standard external bottom bracket bearings set inside these cups. We custom make an adaptor for the Shimano press fit 41 BB92 shells, for more info click here

PF41/BB86/BB92 bottom bracket shell drawing

 BB90 (Road) BB95 (MTB) BB121 (fat bikes): Exclusively used by Trek as an integrated bottom bracket standard, BB90/95-specific bearings press directly into the frame. Cranks with a 24mm spindle and originally intended for external bottom brackets will work with this system. I am not aware of any adaptors for this standard.To sum it up avoid this standard need custom machined solution : /

BB90 BB95

Ok, I am getting bored and tired writing about standards that we can't install the BBSxx motors into.... the next few standards do not have adaptors for BSA, so I won't waste our time with details that don't matter and will update the info on the below standards later if things change.

BBright Direct fit: Avoid this standard custom machine solution : /

BBright PressFit: Avoid this standard custom machine solution : /

386 EVO: Avoid this standard custom machine solution : / 

So as it stands now, the majority of newer standards are incompatible with the BBSxx motors. Here are some simple questions you can ask when selecting a bike to make sure you don't end up with one of these incompatible standards. What type of crank spindle does it have? If the answer is square tapered spindle, you are good to go. What year is the bike? Pre-2012 has a higher chance of being threaded. If you want a full suspension bike it would be a good idea to look for a used one made prior to 2012. Norco brand bikes still have newer post-2012 full suspension models with threaded shells that fit the motor. Is the bottom bracket shell threaded, yes, or no? If yes, the chances are almost certain the BBSxx motors will fit. If its not threaded, proceed with caution and make certain you understand what standard it is. PF30 and BB30 do have adapters available, FSA makes them. We supply an adaptor for BB92 aka PF41.  What width is the bottom bracket? Knowing this allows you to get the proper sized BBSxx motor, 68mm, 73mm, etc... Is the frame carbon? Proceed with caution! The shell thickness increases on carbon frames. Much thicker than steel or aluminum shells. This may be too thick and the motor body hits, not allowing it to slide through. A threaded BB shell on a carbon BB bike usually fits ok because it has the smallest diameter of all the other standards, but with press fit larger diameter shell standards it is not ok. The gap between the motor and the spindle is narrow. The thicker BB opening combined with the thick carbon material is too much. Another trouble with carbon frames is battery mounts. You cannot drill carbon and insert threaded rivet nuts like you can with steel and aluminum.

Its a little confusing out there. Some vendors are offering spacer kits that may make it seem to you that all you need are their bottom bracket spacer kit and you will magically be able to install the BBSxx drive unit into any BB shell 68-73 mm, 73-100 mm, or 100-120 mm. This is confusing and just simply NOT that easy. It is more complicated than just measuring the width of your bottom bracket. A spacer kit isn't going to do jack if the motor doesn't fit the diameter of the shell. Your bike installation may be different requiring a different combo of spacers, chances are good you will need a different spacer other than one provided in the kit and end up using standard 1 or 2.5 mm spacers anyway. Spacers are extremely simple to obtain from your local bike shop and come in a variety of thicknesses, do not make a purchase just because some spacers were whisked into the deal. Vendors do this to make use of the 3 most common motor sizes, 68 mm to fit both 68 and 73 mm, a 100 mm to fit anything from 73 to 100 mm, and a 120 mm to fit anything from 100 to 120 mm.This allows them to stock the motors in 3 sizes and simplify their inventory. The motor actually comes from Bafang in six different widths, 68-73-92-100-110-120 mm. That's right, it comes in 6 different widths, not just 3. The 73, 92, 110 mm sized motors sell slowly and are difficult to obtain from Bafang, this is why the 68, 100, and 120 are found most commonly with vendors.

Most of the time the motor just does not bolt right into your bike the way you hoped. No big deal! There are easily obtainable spacers that bike shops and manufacturers use regularly called bottom bracket spacers. They are available in different thicknesses at any local bike shop or online. We have them too if you need them. You may find that when you put the motor into your bike's frame, it hits the chain stays (the frame tubes that connect to the rear tire) and cannot fit flush against the bottom bracket shell. That is when these bottom bracket spacers come in handy. Just slide these spacers to fill up the gap and get the motor positioned for an optimal chain line.

The photo below is an example of bottom bracket spacers used on a Motobecane Lurch with a 120mm BBSHD motor with a red Lekkie HD bling ring. The shell is a BSA threaded style 100mm wide. The 100mm BBSHD motor hit the frame and could not be installed. A longer 120mm BBSHD motor is used with 5, count them, 1-2-3-4-5, 2.5mm thick bottom bracket spacers filling the 12.5 mm gap. All properly installed with a straight chain line.

motobecane lurch

The above bike had a bottom bracket width of 100mm, but the motor hit against the chain stays and required 12.5mm of spacers to fill the gap between the shell face and prevent the motor from hitting the frame chain stay. This required using a 120mm motor instead of a 100mm. Is very important that you understand the motor needs to fit snugly up against the shell faces on the drive side and avoid hitting the chain stay. I know of one customer who bent the motor casing and dented the frame chain stay while tightening the M33 lock rings with the M33 socket tool without BB spacers filling up the gap. Anyway... here is a simple measurement to reveal if the BBSHD motor and your frame will need any BB spacers. 

The image is upside down due to a website issue click HERE for a better image. You can see that there is enough clearance on this bike for the motor and frame chain stay not to hit each other. If your measurement reveals the motor will hit the frame you can easily determine amount of spacers by moving the ruler away from shell until 2 3/4 inches of clearance is achieved and measure how far the ruler needed to be moved away from the shell to get proper clearance. For a gap of approximatley 8mm and under, order the same size motors as your shell width, for any gap greater than that, you may need to order the next available larger motor size than your shell width. Ok, back to BB shell types...


So here is what you can expect if your bike has either the PF30 or BB30 shells. There are press in adaptors made by FSA (Full Speed Ahead) that will adapt the PF30 and BB30 shells to BSA and allow the BBSxx motors to fit properly. They are available in two widths of 68 mm or 73 mm and for either PF30 or BB30 standards. The picture below is of a BB30 adaptor with choice of 68 mm or 73 mm width.

BB30 to threaded adaptor BBS01 BBS02 BBSHD EMPowered Cycles

Here are the PF30 adaptors below available in 68 mm, or 73 mm width.

PF30 adaptor BBS01 BBS02 BBSHD EMPowered Cycles

You must get these type of adaptors and ignore all other types that may pop up on your google searches. The press in adaptors shown above are the only adaptors you should be getting your hands on and ignore all others because they will not work and waste your time and money. You need this type of adaptor because it mimics a bare english threaded shell that the motor easily mounts into. See through the inside of the shell adaptor below.

Inside view PF30 BB30 to BSA adaptor press in EMPowered Cycles

With these PF30 and BB30 adaptors, the diameter is reduced to fit the BBSxx motors perfectly. All you need to do is press in the appropriate adaptor into the PF30/BB30 bottom bracket shell with a Park Tool Headset Press and you will be able to install the BBSxx motor.

PF30 to BSA shell adaptor BBSHD 1000 watt

You can see from the photo that the adapter is marked L and R for left and right. Start to press in by hand, apply loctite 609 and get your Headset Press handy, or just take it down to your local bike shop and have them remove your cranks and press this bad boy in for you. Most shops would charge 15-30$ for this and save you the cost of tools you may only use once. Insert the Park Tool HHP-2 and begin to slowly press in the adaptor.

 Park Tool HHP-2 EMPowered Cycles

 Make sure the alignment is straight and do not be in a rush.

Park Tool HHP-2 PF30 press fit adaptor EMPowered Cycles

Press in all the way until the press is flush against the BB shell.

PF30 or BB30 to BSA press fit adaptor EMPowered Cycles

Now the PF30 press fit shell looks just like a JIS/BSA threaded BB shell.

PF30 BB30 to BSA adaptor BBSHD EMPowered Cycles

The light at the end of this tunnel is BBSxx goodness. This is going to make one sweet E-bike!

BBSHD PF30 shell with BSA adaptor Lekkie HD bling ring red EMPowered Cycles

In the above picture is a BBSHD 1000 Watt 68 mm motor installed into a 73 mm PF30 shell with a BSA press fit adaptor from FSA. One thing to note is that the 68 mm size is versatile. It can fit both 68 mm and 73 mm BB shells with the spacers provided from EMPowered Cycles free of charge.

Below you can see the perfect chain line achievable with a properly spaced motor and a Lekkie Bling Ring. The chain line is very straight while in 5th gear on the 10 speed rear cassette. Shifts are smooth and precise with a proper chain line. This bike will have no problems using all 10 speeds.

 Perfect chain line Lekkie bling ring HD EMPowered Cycles

This bike is a Specialized Fuse with 3 inch wide tires on 27.5 rims. It turned out to be a very nice e-bike. One of my favorite builds so far. There are many cool bikes like this out there with a PF30 or BB30 bottom bracket shell that can accept the BBSxx mid drive motor. 

Specialized Fuse PF30 BB Shell BBSHD EMPowered Cycles

 Specialized Fuse PF30 BB shell BBSHD EMPowered Cycles

Well it never fails, right now somebody is probably sending an email asking which motor they need to get for their bike, the 68 mm, the 100 mm or the 120 mm ??? I will try my best to help, but please take a moment to find out what type of shell your bike has and be able to answer 3 simple questions for yourself. What style BB shell does your bike have? The width? The diameter? It is up to YOU to know these basic details. These 3 simple details can make or break your BBSxx build. 

So this whole article can be summed up to this...

- Know the year your bike was made, pre or post 2012.

- Look for threaded JIS/BSA, PF30,  BB30, Shimano Press Fit 41 BB92

- Know the width, diameter, and standard of your bottom bracket shell.

- A spacer kit will not solve your problems! It takes a little ingenuity and patience to install the BBSxx motors into some bikes.








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