nervar bb troubles
hi all. I'm trying to restore an old Italian 10spd oddity, a Romeo from Romeo bikes in Rome, circa 1975. As it's a custom in-house build, the components are a really mixed bag: lots of campy, weinmann brakes, and nervar cranks and bb.
my problem: the drive-side bb threads are damaged (lbs nightmare, don't ask), making it so far impossible to reinstall the fixed cup.. the bb spindle is stamped "nervar 117", no other markers anywhere, and both cups are right-hand threaded, consistent with the older french standard (which of course caused the bb to loosen over time, which caused me to try and fix it, etc..). I'm considering tapping the bb shell out to the slightly larger italian thread, but given that the bike is such a mix of standards (tubing is almost certainly italian), is there any chance that the nervar bb could already be italian threaded? did french companies ever make such a bb? it seems weird that a cusom hand-built-in-italy frame would have french threads in the bb. maybe someone replaced just the spindle and the cups are actually italian? I have no calipers and no italian bb to check it with. is this a good idea? what would some of the more experienced mechanics out there do? can you repair a few crossed/mashed threads with special files or something, or is tapping the only way to go? and if it turns out to be italian thread, is there any larger size I can tap the shell to? thanks for your help.
The Italian style also used two right-threaded cups, IIRC, so you won't be solving that issue. You can check by measuring... French threading is 35mm x 25.4TPI, and Italian is 36mmx24TPI. Italian style will also have a 70mm wide BB shell, as opposed to 68mm. (Meaning it's unlikely just the spindle had been replaced.)
I'd say try to chase out the threads, rather than completely recut them. Just use a tap, but of the same size as the existing threads, to clear out the damage. If it's already Italian threaded, that's pretty much your only option, anyway, as I know of no larger size cups.
thanks for the advice--I realized that Italian cups would also both be right-handed, and then measured the shell to confirm it was french threaded. then I dared a second look at the threads and realized they weren't all that bad.. brought out the smallest metal files I could find (they were tiny), and managed to fix some of the crossed threads, or at least break them in a more accommodating way. by very gently and slowly threading the cup back in, checking every 1/8th of a turn, and going back and forth on a section once I got it to turn to lubricate and cut the right path back in I was able to get the cup in again. probably won't handle another de/re-install, but it's very tight and now the whole thing is overhauled and reassembled, and spins beautifully! this after googling for a french-threaded die to chase the threads fruitlessly.. does someone online carry those things? seems pretty obscure..
var still makes the dies, but for what you'll pay you might as well buy a bike of similar quality. you'd be surprised at how much abuse a steel bb shell can take.