Edbonsky

Hi all,
Long time reader, first time poster.
I'm fairly new at bike building and I'm working on my second bike.
First bike came with a cottered crank and choosing a rear hub was relatively easy.
The frameset I have now came with a shimano bb which I believe is a cone and cover (?), the rear drop out spacing of the frame is 126mm. BB has marking 36x24 and measures 115mm from outside spindle and is square tapered.

My question is probably very straight forward. I'm wondering what crankset (2 ring) I should be looking for (#BDC?) if I'm buying on ebay and if the # of speed freewheel will effect that decision or vis versa.

Any other information about the frame needed to make suggestions? I would post photos but I'm under 10 posts.

Does anyone know of any discussions about this topic?

Thanks in advance.

wrk101

You are doing it backwards. BBs are cheap, $10 for a brand new UN26 cartridge.

You buy the crankset first, then get the right length BB to fit your crank.

Sheldon Brown has a list of bb spindle lengths, not complete.

Edbonsky

I see! Thanks for clarifying that.

Dfrost 

@Edbonsky,

Where are you located? If you’re in or near a major metropolitan area, there’s probably a bike co-op, or other used bike emporium with used cranksets that will be much less expensive then most Ebay sales.

And watch the C&V Sales subforum, where there are frequent used cranksets offered, like the one in the second link below. C&V folks are likely to help you determine the correct BB length.

https://www.bikeforums.net/classic-vintage-sales/

Nitto, Thomson, Sugino VP

Here’s everything you need to know about chainline:

https://www.sheldonbrown.com/chainline.html

jimmuller 

Welcome to BF posting.

No one has mentioned it yet (unless my eyes glazed over) but your BB is a fairly typical Italian. Measure the shell width and you'll find it 70mm instead of the English/ISO 68mm. The drive-side threads will be right-hand, like a French BB, instead of left-hand like most everything else. If you go with a cartridge make sure it is spec'ed as Italian.

While I agree that you are "going about it backwards", you can still possibly use that BB. You should be looking for a crank that suits the style and preferred gearing, for example if you want a compact double to run a small ring smaller than 42T, or if you are stylin' up a cool Italian frame with as many original-type components as you can manage. Most cranks are similar enough that to within a mm or two any spindle length will do, though there are exceptions which you can recognize by doing some research on a case-by-case basis. When you find a good crank you can try it. If the BB doesn't work you can always pick up a cartridge anyway and be none the poorer than you would have been if you'd just bought a cartridge in the first place.

Show us the bike!

Edbonsky

Thanks Dfrost for the tip.
I'm in Toronto so I'm sure there's something I could find.

Edbonsky

Thanks, jimmuller.

I'll keep that in mind if I end up swapping out the BB.
I'd also love to post photos of my bike once I hit this magical 10 posts =)