This is the one I want to order: https://www.bike-mailorder.com/products/thun-efficient-jive-thompson-einpresslager-oe40mm?variant=50589190750472
The 40mm diameter is right but my bottom bracket shell is 70mm long
With normal BSA I think it wouldn't be a problem as they're secured by threads, but with these ones i'm not sure if the 2mm of play will lead to the bottom bracket not being squeezed tight enough by the endcaps?
Also a side question: How do I find out the chain line/required BB spindle length of an unknown chinese crankset when there''s no documentation?
by KannstDuNachrichten
2 Comments
you’ll need a 70mm version, you’re correct about the press fit not mating well enough.
https://www.sheldonbrown.com/cribsheet-unthreaded-bottombrackets.html
also includes chainline info
It might work, the plastic housing presses over the bearing, holding it in place. The 2mm probably won’t affect the retention, but will put the NDS crank closer to the frame.
I would be more inclined to face the shell back to 68mm if there are no other BB choices (which I suspect is the case). This poses its own problem, as the facing tools I’ve used all require some kind of pilot fitting to centre the cutter. I doubt many shops will have one for a 40mm bore.
If you have access to a BSA frame and some square taper BBs, you could test fit the crank with different length spindles to see what gives a suitable chain line.