Originally Posted by
FBinNY
If they only give overall length, and don't mention any asymmetry, or difference in right and left side, than assume they're symmetric. ...
O.k., maybe that's the code I was looking for:
"All cartridges are symmetric unless noted otherwise."
I've never seen one that's noted otherwise, and I think I've looked at all the available JIS cartridges by now. So apparently all JIS cartridges are symmetric, even though the cup-and-cone JIS spindles they replace were usually asymmetric.
Then I can't do what you said about finding a cartridge with the same R/L difference as my spindle, since my spindle is asymmetric. I'll have to buy a symmetric cartridge with the equivalent right-side length.
My spindle is 32+52+36=120. The symmetric equivalent would be 36+52+36=124. So I should choose a cartridge as close to that as possible, which would be about 122.
That should take care of the other issue as well. The extra 2mm on the left should mean that there's no chance of the crank contacting the shell even though the left cup of the 68mm cartridge is counter-sunk into my 70mm shell. I just have to make sure I get one with no left flange, or a plastic left flange that I can trim off.
Thanks very much for your patience and help with this.