Track bikes commonly had 68mm bottom brackets in Italian threading, some even had 65 to reduce the bb width (supposed to be an advantage for sprint events). My Masi track bike from the 70s is 68mm.
I remember that when we first started using some Shimano BB's, they wound up being a bit long. The Japanese made their spindles to match bb's that were 70mm. The Campagnolo bb's were about .5mm less, apparently to allow for the facing of the bb shell that reduced the width to just under 70mm.
Jim Allen the CycleSmiths Ranchita, CA, USA
oroboyz@aol.com wrote:
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> <<...Italian threading (RH threads on fixed cup) but a
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> 68mm shell. >>
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> Hey Dean:
> This is not that unusual...
> Many shells came through undersized and then became more so after "facing".
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>
>
> Dale Brown
> Greensboro, North Carolina USA
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>
>
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>
> -----Original Message-----
> From: Dean Nixon <vintage.lugged@gmail.com>
> To: classicrendezvous@bikelist.org
> Sent: Sat, Jan 16, 2010 7:18 pm
> Subject: [CR] Circa '68 Masi Pista BB Shell Questions
>
>
> Hello everyone,
>
>
>
> I was in the process of installing a campagnolo BB (Italian threaded,
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> 70-P-120 spindle, thin walled cups) on a circa late 60's Masi pista when I
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> noticed that the adjustable cup protruding a little more than normal from
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> the BB shell. I pulled out the calipers and sure enough the shell is 68mm
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> wide. Now I'm confused. Italian threading (RH threads on fixed cup) but a
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> 68mm shell. A few things are going through my mind:
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>
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> 1) Shell has been shortened to accommodate a 68mm spindle?
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> 2) BB should be the 'thick walled cups' version
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> 3) BB has mismatched parts (different years but same model or different
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> models same year)
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> The surprising thing is that the chain-line looks to be spot on. Has anyone
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> experienced this issue before or have some helpful information?
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>
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> Thank you,
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> Dean Nixon
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> Toronto, Canada