I decided to "temporarily" play with some Microshift brifters and Shimano front/rear derailleurs on my '81 PXN10E (I'll be going back to the OE down tube friction shifters after RAGBRAI or possibly much sooner depending on replies here). If you are still reading this as a C&Ver, thanks!

Everything in the rear works great, after hours of tweaking. I had to rig a shim on the 28mm French seat tube to accommodate the 32-34mm FD clamp, but the FD is mounted rock solid now. I followed the Park Tool Front Derailleur adjustment (Front Derailleur Adjustment | Park Tool) along with a few other sites. I believed I had it aligned correctly, but since I was experience some chain rubbing, I double, triple, quadruple checked my alignments.

I would sometimes experience chain rub on the cage with my original Peugeot branded Simplex FD when going big/big or small/small, but a little trimming with the downtube shifter would clear that up (I did not realize how much I appreciated that "friction" feature until yesterday!). And I never had any issues with front shifting on my original shifters outside that expected one. But with the new Shimano FD, I was getting chain rub on the cage (with either chainring) on all but one or two middle rear cogs. So I started taking a much closer look. First, my original FD cage is about 1.5 to 2mm wider where the chain leaves heading back to the rear. But more importantly, I noticed that as I adjusted the cable tension, I found that the chain was not rubbing during the entire spin of the crank. It was only rubbing when the chain rings were at certain positions. I'm guessing I probably didn't notice this before because my original FD cage was wider. With the narrower new FD cage, it became more evident.

So I found an article by Sheldon that seemed to be exactly what I needed.

https://www.sheldonbrown.com/straighten-chw.html

For those who'd rather not click through and read the whole article (I'm guessing if you're reading this post there's a good chance you've read that one too!), here's where I started:



1) The bottom-bracket axle may be bent. This is not very likely, but you should still check it first:

A. Use a marker to mark the part of the outer chainwheel which is farthest out.
B. Remove the right crank from the axle.
C. Reinstall the right crank 180 degrees from the way it was previously installed, i.e., facing the same way as the left crank.
D. Spin the cranks and see which part is farthest out. If it is the part you marked, then you have eliminated the axle as the source of the problem. If it is opposite the mark, the axle is indeed bent, and you need to replace it.
E. Re-install the right crank in its normal orientation.

For step A, instead of "seeing" which part of the "chainwheel" was furthest out, I simply marked the spot on the chainring, near the teeth, where the rubbing on the cage was happening. The "spot" spanned several teeth, and I just used an orange crayon to mark the arc of the rub. For step D, sure enough, I was getting rub on the exact opposite side of the chainring. The orange crayon marks were 180 degrees away from the new rub point. There's a bit over 1.5mm (my measurements aren't most precise) difference between the outermost point of the chain as it just rubs against the cage and the gap between the chain and the cage when the crank is rotated 180 degrees

So that leads me to believe I have a bent bottom bracket spindle. Here are a couple of pics from a month ago when I had the BB apart (I do not have it apart right now)




For now, I'm going to put the original wider-cage Simplex front derailleur back on to see if I can make the brifter indexing work with that. If not, I'll probably go back to the down-tube shifter for the front and leave the rear on the brifter. But long term, it would be nice to pursue getting things straightened "down there" to make things smoother front and rear.

So:

1) Was Sheldon right about my BB spindle? Could it possibly be something else? As Sheldon said, a bent spindle is not very likely.
2) Besides trying to bend both the chainrings to counteract a bend in the spindle, or trying to bend the FD cage open wider, which all sounds bad, I'm guessing the only reasonable option is to replace the spindle (or the entire bottom bracket), right?
3) I'm having a hard time finding just a 118mm square taper spindle or even a reasonably priced vintage bottom bracket assembly that I could just steal the spindle from. Are these that really that rare?
4) Since I believe I have French threading (right/right) and 118mm, it seems like my options are pretty limited. Is there an alternative that won't cost me an arm and a leg? Or should I just live with it?