Bottom bracket confusion

[MajorMantra]

Apologies for the boring question but my research hasn't answered it...

I'm considering changing the chainset and BB on my 1980s Bianchi Super Leggera. This doesn't hold any particular terror since I've had BBs on other bikes in and out 3 times before. However, I am a bit puzzled about this one.

It says 36x24t on the BB so I take it that it's an Italian thread. The strange part is that the BB shell measures 68mm across. Is there such a thing as a 68mm Italian BB? Will a new Shimano BB-5500 109x70 Italian fit and will it need a spacer?

Cheers,
Matthew

 

[MartinC]

36x24 is definitely Italian. Don't know how you measured the BB shell but the difference between 68 and 70 mm is small so it could just be inaccuracy in the measuring. If the BB shell has been faced you could easily lose a mm or two of the width. It's unlikely to matter - a new BB should go in tightly enough and if it doesn't then you can washer it.

 

[MajorMantra]

Thanks for the reply. I got a similar one on another forum so I think I should be alright. When I measured the shell for about the fifth time I figured it was actually more like 69mm so I think it is indeed possible that it's been faced a bit enthusiastically.

Cheers,
Matthew