Originally Posted by
billytwosheds
Look for markings on the fixed cup.
Sheldon Brown's page can be useful in understanding the differences between BB shells, cups, etc.
https://www.sheldonbrown.com/gloss_bo-z.html#bottom
Right-hand thread on both cups still tells me French.
But I have known to be wrong before.
Re: installing the new French BB, I would be wary of trying to reform deformed threads from French > ISO > French.
The threads on the BB in your pic look a little mowed down, which again makes me think it was forced in.
Tend to agree shell was originally threaded French. Only thing that seems contrary to this is Sheldon Brown has a chart that shows what happens when you try to mismatch BB and threaded shells. For French shell and English BB it says BB goes in loose. So, not sure why I would have so much trouble putting in French now.
Seems like only two choices:
1. try to insert the French BB with fingers crossed.
2. try to locate an old BB with English threading and flanged cup on non drive side (and then locate adjustable cup that fits the BB body). This sound painful.
3. Wildcard choice...install loose ball BB with two adjustable cups and loctitie? Doable?