Hi peeps,
Is there any way to differentiate an Italian BB shell threading? Probably any signs or markings. Read similar thread from cyclingforum.com and only way to spot an Italian/British is by measuring the bb shell - Italian bb shell 70mm wide while British bb shell 68cm wide. Another way by looking at the bb cup markings which install on the shell.

What if there's no bb cup, just an empty frame set? Would be great if someone could share more infos on verifying vintage frame.

Thanks

Find any british bb cup, if it "drops" in, without engaging threads, the shell is probably italian threaded. Or find any italian cup, if it won't begin to engage because it's too big, the shell is probably english threaded. Unless it's french or swiss

You're right on the shell measurement--70mm shell would be Italian, 68mm is other. That's probably the easiest way to tell, if you have an empty frameset and no other bb cups handy.

As folks are indicating, BB shell width is the first thing to check. The (careful) cup checks are also a good idea.

If you measure the I.D. of the BB shell threads, British threads should be about 33.8 mm or so, whereas Italian threads should be more like 34.8 mm. I.D.

Remember also that sometimes stripped non-Italian threads were reamed out / re-tapped to Italian as a repair, though, so a 68 mm wide Italian-thread BB can occur on an old frame. I think there were also some Italian marques (certain very old Cinellis, for example, iirc? Not to mention their 74 mm ones...) that had 68 mm shells that were Italian threading.

Edit: French/Swiss BB shell threads should be about .2 mm larger than BSC, or approx. 35 mm I.D. Unfortunately, that is very close to BSC (no surprise), and the I.D.s can vary a bit, so that's not a great way to distinguish French/Swiss from BSC on used frames.

My '89 waterford paramount may be a re-tapped example, shell width is 67mm, threading is italian.

This should only be considered a "screening" test. I've seen both British and Italian thread BB shells ranging in width from 65mm to 74mm.

It does engage but only at beginning and then stuck. Works fine (smooth insertion) on other Italian bb shell threading bike with similar bb. Frame is NOS condition.

What's I.D mean? Sorry, I'm a newbie in vintage bikes

chase the threads?

can you please explain more about chase threads?

Refacing can often remove material and result in a deceptive measurement.

I.D. is inside diameter. Chasing threads means to run the correct tap through them to clean up the threads. A tap is a tool which cuts threads, so you need to make sure you are using the right one, and using it correctly.

Thanks Pars for your clarification

You might want to just post up some pics of the bike itself. There are are a lot of people here who are amazing in their ability to identify manufacturers/models (seriously, I mean, savant-like).

And some of us are just idiots