the reason why the bb ismt a standard size, is that it titanium tubeing
note, the smmooth bb i have came with the powerlite i buyed
note the bearings will be imperial, not metric
the spingle is.62 of an inch
15.90mm
-say 16mm
so you need to go 16mm to the id of the cups the bearings need to be as wide as the cups
note, a eurobb wont fit cos ti isnt available that size, or guage to cut a thread in
-us bb size either'
the cup is specufic to a stock size beasring to spindle - else it wouldn't be there - at that size i.d.