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Anyone know of any that fit a 73mm threaded BB for SRAM cranksets?
And feel free to discuss the idea in general. Combined with a reach adjust headset I believe you could get some meaningful changes that would feel quite different to offset bushings or longer stems.
Look at Eccentrikizer type solutions designed to allow frames to be run SS that weren't designed for it.
You still only get about 1cm movement though (5mm in any direction from central position)
meaningful changes
A shimano hollowtech axle is 24mm, the inside diameter of a standard threaded BB is ~34mm, that leaves 10mm to play with, 5mm either side, now assuming the BB cup has to have 'some' material to it as well, lets be generous and say total of 1mm (likely more in reality), that leaves you 4mm either side at best to shuffle the spindle around, and that's with it touching the inside of the cup at the extremes.
If you consider moving the BB by 4mm to provide meaningful changes crack on. I have an Trickstuff Exzentriker and from one extreme to the other is barely noticeable, ~3mm in either direction.
You can get a little bit more using inserts for bigger shells, like pressfit shells or traditional eccentrics, but they're still fairly small adjustments overall, and if you have a threaded shell then short of chopping it out and welding in a new one you're out of luck.
Funnily enough I had a similar idea and built myself a frame to test things out with, you can have a read up over here...
http://www.spanner.org.uk/2018/09/are-29ers-and-low-bottom-brackets-faster-part-i/
and...
http://www.spanner.org.uk/2018/09/are-29ers-and-low-bottom-brackets-faster-part-ii/
...if you're interested.