efanwick

I'm trying to take my old frame from my Silver Shadow that I love and reuse the frame still in great shape. The bottom where the bottom bracket goes doesn't have threads. What kind of bottom bracket should I be looking for for this frame?

scarlson 

Hm, odd. Do you know how the original bottom bracket was secured in place? Or don't you have original parts?

The frame looks decent quality, from information I can gather, so likely worth saving as you say.

There were a number of threadless bottom bracket systems floating around the market in the '70s and '80s, many of which employed standard diameter shells. These can often be tapped with the appropriate threading and used with a normal bottom bracket. The problem is, while many bike shops will have taps, some won't want to use them to cut new threads in a completely unthreaded bottom bracket because of the wear on their tooling. A framebuilder could also do this for you.

Another alternative is the Velo-Orange threadless bottom bracket, linked here. You should measure the shell diameter to make sure it will fit, before you commit any money, because they are a good bit more expensive than other bottom brackets of comparable quality.

That said, if you live close by the Boston area, I have a set of cheap taps and I could try to do it for you.

nlerner

Could be an Ashtabula-style crankset?

scarlson 

I don't think so. The Vista Silver Shadow, in all the pictures, I can find, has an ordinary 3-piece crank. Looks square-taper, but maybe it's something proprietary like old Viscounts?

Chuckk

I think they use the Shimano Altus/Selecta BB
https://www.bikeforums.net/classic-v...s-selecta.html