bottom bracket adjustable cup sticking out of shell

I've just installed a shimano BB-6500 cartridge bottom bracket that came with some second hand cranks

With just the drive side fully inserted the spindle turns smoothly but if I try to insert the adjustable cup fully, the bearings become rough and index

To keep the bearings smooth I have about 4mm of thread showing proud of the bb shell . Surely this can't be right? The cranks will install fine but it looks strange . Is it because the bearings are knackered that I can't fully insert the adjustable cup?

Thanks

Ps I have tried just the adjustable cup on it's own and it goes in fully no problem so the threads are fine. I have tried two other non compatible bb's and they both work fine

Sorry for poor photo quality

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73mm bb in 68mm shell?

Edit: I've never had to use bb spacers, but assume they'll be fine here?

Nope theyre both 68mm . Thought about spacers but I'd need a few. Doesnt seem like it should have to need them if it was installed correctly but I've tried 3 times now !

BB6500 is a cartridge unit (just like a UN55 or UN72 etc) so the non-driveside cup should have no effect on the bearings.

If it does something is amiss.

Sounds like you might have cross threaded the non-drive side cup - that would explain why you can't screw it in fully, but it shouldn't affect the turning of the spindle...

it certainly didn't feel cross threaded as i could go all the way in easily, it just caused the spindle to stick ...

I took the whole thing out this morning , cleaned the threads again and greased the inside of the adjustable cup as well - it has a rubber seal around the inside that I thought maybe causing resistance.

I screwed the cup all the way in and out again a few times. It seems to have fixed the problem to the point I can get the cup in about 1mm off the shell, which I could fix with a spacer. Not sure what the problem was / is but seems ok for now . Bearings don't feel amazingly smooth but not really noticible when pedaling .

Sounds like you may have chased the threads out with the new cups? Was there a lot of old crud/grease/thread lock/rust still about in the shell threads, from the old bb? Might that have clogged up either side?

Glad you're back on the road though!

Edit: ignore threads question, as I just re-read above.

Cheers ! Seems ok now