Stating a fact: 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.
I purchased a BBS02 from Johnnynerdout, but it didn't fit my Cannondale Hybrid, which has a slightly smaller bottom bracket shaft diameter. So now I am looking for a used bike which matches that standard. It is hard to find the bottom bracket specs for potential bikes. For example. the Trek 7.3 FX hybrid. Any advice would be appreciated.
Looking at a Norco Bush Pilot bike with Bottom Bracket
FSA BB-7420ST Cartridge
Will the BBS02 fit this bike?
Alternative: A Gary Ficher Advance
Can't find any specs on the bottom bracket.
Any experience installing a BBS02 on this model?
I'm using 24in full suspension MTB frames. See photo below.
Go with an IGH drive system. I recommend the shorter 24in wheels because electric motors work better at high RPMs and high torque. You're lugging the motor with 26in or 700 wheels. Bad for electric motor. Not even necessary to lug it out with taller wheels, since you can run a single speed on a Bafang and use the PAS for speed and minimize the pedaling. 24in keeps you in lower gear range all the time. Actually a lot of ebikes use even smaller tires than 24.
youd likely need to contact the manufacturer to get the specification, otherwise its a shot in the dark
So back to my Kuwahara Eclipse. I can't find ang specs for the inside diameter of the bottom bracket. Will the BBS02 motor shaft fit this bike?
I had hoped the 95% number is true, but am just unlucky I guess. The first 2 bikes I wanted to mount the motor on were fails, as they are Cannondale (one I own) and Trek (one I found second hand). As you can see from the linked article, Trek bikes are incompatible with the BBS02. And when we tried to mount the motor on my Cannondale Quick-4 it wouldn' t fit. The Bottom Bracket "socket" was a couple mmm too small. So even though it says in this article (below) that it should fit, we could not figure out why it did not.
https://www.empoweredcycles.com/blogs/news/101474694-bottom-bracket-standards-and-bafang-mid-drive-motors#
"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 :"
It is not just the bottom bracket to watch out for...some recent bikes have been trending towards bigger tires, shorter chainstays, boost spacing....
This means that the chainstays begin flaring out from the bottom bracket sooner, and have to make more drastic angles than older designs, thus not leaving a lot of room for larger chain rings...assuming the motor does not collide with the chainstay first.
So, even if the motor clears the frame you may have to choose between a smaller chain ring with proper chain-line...or go with a larger ring and throw the chain line way out.
On one bike I had to use a .090" spacer between motor and chain ring in order to get a decent number of teeth.
yeah 95% of bikes are standard BB sizes which the motor fits on, there will be those odd exceptions. its not hard to find a good mtb frame which suits you, and hardtails are generally easier to convert. this chart is useful for sifting through BB stuff. https://wheelsmfg.com/bb-standards
Here is finally some useful information. Note that this states specifically that the Bafang motor will not fit either Cannondale or Trek bikes. https://www.empoweredcycles.com/blogs/news/101474694-bottom-bracket-standards-and-bafang-mid-drive-motors#:~:text=Next%20you%20need%20to%20know,tapered%20spindle%22%2C%20ISO%2FEnglish