About six months ago, Bafang apparently changed the manufacturing process for the Bafang HD rotor shafts (BBSHD). The result was that, in my opinion, the heat treating of the shafts caused brittle juncture where the 8mm shaft transitions to the helical gear section. That in turn caused many motors in the field to experience breakage at this transition.
They then came up with a solution by re-designing the Bafang HD rotor shaft to to be much more durable and a more appropriate design for the high torque/high speed motor drive. The new design now features an 11mm shaft section through the lamination stack and a bearing journal that is 9mm in diameter.
Now the dilemma is these new style rotors are much more durable but, as supplied by Bafang won’t fit the older style motor housings. California Ebike has many customers that need these rotors replaced but we also do not want to have them breaking again. So, we did a bit of research and determined that by removing the 629 bearing supplied by Bafang, we could then replace with a 609 bearing + 1mm spacer to fit the old style housings. So far all is working well and we will update the website so our customers can order the appropriate rotor replacement. Old or New style.
Check out the video showing how to install new bearing.