So I have an older english thread bike, with a weird 70mm BB shell. Would it be possible to use a 68mm bottom braket in it or can I make the italian thread work? Aren't they pretty close?

thanks.

get phil wood bb cups but the measurement sound italian

Italian BB's are 73mm wide, English are 68mm. The width is arbitrary, as long as you choose the correct spindle length for the purpose. The issue is the threading. If it's Italian an English BB will probably just fall right in, and not engage the threads. It's hard to crossthread an Italian BB with an English cup.

just use a 70mm italian spindle. you don't need to match up the spindle to cups . . . i asked myself the same question a few years ago. i have a 1954ish holdsworth la quelda that for some reason a 68mm spindle does not work in. i tried, out of curiousity, a 70mm spindle and it worked perfectly. still running it a few years later with no problems.

also, absolutely you cannot make italian threaded cups work in an english threaded BB.

and don't worry, i haven't forgotten about that TA chainring. as soon as i get back from visiting my folks i'll check the teeth count and send you a picture.

also, i have never seen a 73mm italian shell in my life.

there's a bunch of things you could do..

-you could mix and match spindles and cups until you find a combo that works..
-you could use a phil wood bb with no problem (they thread all the way iinto the shell and do not have cups that contact the outer surface of the shell)
-or you could have a framebuilder or bike shop with bb facing equipment take your shell down 1mm on each side, making it 68mm

Or you could just buy the proper bottom bracket.

But THATS the thing. There is not proper bottom braket. It was for cottered, and I'm switching to square taper. 70mm english thread is not a common size, usually 68 english, 70 italian. Which makes your comment a moot point.

apotnolid, rad thanks. I came across a NOS shimano for $10, thats italian. It's worth a shot. As for the TA chainweels, no problem. I get a bit excited, so sorry for the second PM.

Everyone else, thanks for the help. Phil is sorta out of the question because of price. This was a $20 bike, that I'm trying to convert to SS for my wife. I'm keeping this on on the cheap. That BB would be worth more than the whole bike when I finished.

How is the width of the BB shell arbritrary? There's also 70mm as well.

Oh please. If you already know anything what's the point in asking? Which makes your entire thread moot. Go to your LBS and ask them if they can order you a 70mm english BB.

They exist, they're just not that common. I know this because I bought one for my weird ass bianchi frame which took a 70mm/english.

Uhhhh, yeah, okay. Thanks for that.

ANYWAY, I found an old cup an cone BB with a square taper axle. I'm gonna give that one a try since it was free.