Hello. I have a 1990ish ross centaur frame I want to make into a single speed. I got it as just a frame set so I don't have the original components.

I want to buy a new bottom bracket (prob just a basic shimano), crankset (basic sugino or similar), and i was thinking to buy a mavic cxp22 wheelset with a flip flop track hub from velomine. the rears spacing on the frame is 130mm and velomine says they'll add axle spacers for free so I was just going to do that rather than cold set or squeeze it.

now my question is: How can I determine spindle length that will give me a proper chainline? i don't have any of these parts in my possession and don't have the original bb to even know where that one was at. I want to try to do this myself and find some of the stuff used or for deals online and want to try to avoid getting bailed out by lbs if possible.

BB length is determined by the crank you are going to use.

the crankset is the only thing that matters? I don't have to be worried about being too tight against the chainstays and the ring hitting it? or having a chainline that I can't get straight because the spindle sticks out too far or is too short?

so i can just pick out a crankset i like, get a bottom bracket that has the appropriate length for that crankset and not worry if I'll get a straight chainline with whatever hub is on the rear?

Right!

Look at the BB shell.
Now look at the shell for most any other bike.

Unless you have some oddball bike, it's 68MM wide and in the exact center of the bike.

I looked up the bike and on bikepedia.com
I only saw a 93, 94 & 98.
The 98 was an IG hub.

The 93 & 94 had a not normal 20-30-42 tooth chain rings with an 11-19 cassette.

Does your bike have those relatively tiny chain rings?
IF it does, make sure you have clearance against the chain stay if going to larger rings.
Depending on how the chain stays bend immediately behind the BB shell, that "might" be an issue.

I don't know, i only have the frameset. i found of pic of the exact frame i have but the ocmplete bike

here's a thread where someone shows a drive side pic of a pink centaur like mine
https://www.bikeforums.net/showthread...=1#post6555651

i found this listing for one for sale somewhere that states this information:
"ross-centaur-road-bike-12-speed-25th-anniversary-1965-1990-has-araya-quick-release-wheels-27x1-1-4-tires-hene-shin-27x1-1-8-complete-shimano-light-action-gear-train&shifter-chrome-molloy-frame-total-weight-27-lbs"
https://www.americanlisted.com/kentuc..._12615940.html



and here's a nother pic i found that someone converted




another complete pic

Obviously the LARGE ring clears and it doesn't appear the chain stays have any "abnormal" bends, but I'm not sure if the "dent" in the chain stay is normal or "added" for clearance.

I'm ignorant about track hubs etc. and any specific problems they might impose, so at this point I'd best bow out.

Too me though, it looks like most any "plain vanilla" road bike from that era.

what do you do if you have an old crankset you want to re-use but you don't know what length spindle is supposed to be used with it?