(solved) Different kinds of square taper BBs: JIS, ISO -- which is TSDZ2? Data is conflicting

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xtinctionRebeller   10 W

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(solved) Different kinds of square taper BBs: JIS, ISO -- which is TSDZ2? Data is conflicting

Post by xtinctionRebeller » Mar 23 2020 4:45pm

I need to know what specs to look for when replacing a Tongsheng TSDZ2 crank. Everyone says "square taper" and stops there, but there are 3 2 different kinds of square taper: The measurements above are "the width across the narrowest part of the flats (end of spindle)".

This data is somewhat conflicting, because zro-1 on this board says JIS is compatible with Bafang, and a BNI tool is said to be compatible with Bosch (edit: the tool does both BNI & square tapered but this doesn't mean BNI is square tapered). At the same time, the Lekkie Buzz Bars are compatible with both Bosch and Bafang (and I've read in other places that Tongsheng is compatible with Bafang). This can't all be true at the same time.

I'm tempted to assume Tongsheng (obviously Asian) is JIS, since JIS is for Asia. This implies Lekkie can't claim their Buzz Bars to replace both Bosch (German/BNI) and Bafang (Asian/JIS).

Update:
I think I have it sorted now. Indeed there is some misinfo out there (the Lekkie catalog in particular). Here it says: "These cranks are ISIS fit for Bosch Performance, Performance CX and older type Active Line. They will not fit the 2018+ Active Line / Active Line Plus motor which uses the smaller Bosch BNI Interface." So this implies the star interfaces are:
  • ISIS - the most common star interface spanning many brands
  • BNI - a "Bosch Spindle Interface" apparently smaller but similar to ISIS
Bosch may have had some square tapered cranks at some point but such things are rare in any case.

JIS cranks could almost be installed on an ISO spindle, but they would bottom out which is not good (fit too loose):

Image

rationale:

Image

This is Bosch BNI (10 teeth):

Image

This is the ISIS design (also 10 teeth):

Image

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