Current Projects chat and miscellany

Just posted this in mechanical and fixing, but I might find more help here... It is after all related to my current project...

May I "pirate" this thread rather than openning a new one for a BB cup related question please?

I have installed a BB this WE on my current project.
The non drive side cup went in way too easily compared to what I'm used to. It is a british frame with british threaded BB shell, and I double checked the TPI reference on the cups, it is british as well. On the drive side, it went in with the usual little resistance, all well faced, perfect...

But as I said the non drive side cup when too easily, the first 2 milimeters of thread don't even engage the cup, it almost just slides in. Then the threads engage, but it feels very loose. Half way through, if you move the cup up and down, it has a bit of play.

I installed the BB regardless, and when the lockring is on, it feels firm, but I am afraid that when I ride the bike, the force applied to the cranks is likely to make it all move a bit, and possibly aggravate what seems to be like a tired thread within the shell.

Should I re-fit the cup using PTFE tape?

Or is there another trick I can use? It is a classic build, and this is a campag BB with campag cranks, it would frustrate me to go for sealed BB here, or worst, threadless...

Thanks!

Loic