conspiratemus1

I have a left-threaded lock ring that you can have free if you find you need it. Our old tandem came with lock rings on both sides of both (cartridge) bottom brackets so that you could adjust the chain line a few mm each way. Both BBs have long since worn out but I kept the lock rings for some weird reason.

The right cup will tend to screw itself in tighter from precession. You wondered if it was meant just to drive in and stop. I don’t like this idea because the cup will always be trying to force new threads into the shell, even if the ones there now are just right. But if you need the cup to stop shy of the bottom of the threads, you definitely need a lock ring.

Anyway, PM me if you want one. We’re supposed to be staying at home except for essential shopping here till 22 Feb., and our local post office has had Covid outbreaks, so I can’t ethically regard this as an essential errand. (I have to go to the p.o. to mail it, Customs paper work.) From the number of cars on the road, I don’t think many people are staying home. Still...

Edit: I see from @shoota’s recent post that his fixed cup goes in till it’s flush with the shell. So no room for a lock ring. Guess you just drive it till it stops. Precession keeps it there. Sorry for the red herring.