Building my first bike from the bottom up - Crankset/bottom bracket questions
I recently purchased a Bilenky Nor'easter frameset from a dude on craigslist (picture attached), and have plans to build it into a fixed gear bike to use for commuting and around town, and in all kinds of Philadelphia weather. I'd also be using this bike for training purposes and longer rides, to work on my fitness and maybe start racing next spring. For my daily/commute I currently ride an old Peugeot converted to a single-speed with 42t in front and 16 rear, which is comfortable enough with a free wheel, but I think I would need to change the gearing on my new build-up for more effective spinning.
I've been wanting to build myself a fixed-gear bike since moving to Philly, and have lusted after Bilenky bikes for about as long. This is a strange marriage of both desires - a fixed gear build-up on a cyclocross frame. I've never built a bike before, though, so this is all new to me, and I need some guidance.
After doing some homework on the internetz, and consulting Sheldon Brown's site, I remain a little confused about planning out the drivetrain. I'd like to use a SRAM Omnium crankset/GXP BB -- but I'm not sure whether I can use this crankset/BB combination on my frame, which has 130mm spacing between the chainstays. Do I need a longer BB on this frame? The guy I bought it from recommended I use a 118x68 square taper BB. But 118 seems giant, for a fixed gear. Does it have to be that big in order to maintain a straight chainline?
Also, I'm assuming it takes a British/ISO BB, but maybe I shouldn't assume that? How do I determine the threading on my BB shell?
I need to figure out if it is even possible for me to use an external bearing BB like the GXP on this frame. The Omnium crankset is right in my budget and seems to have gotten consistently good reviews, so I'd really like to use it.
After I sort out the crank/BB/rear cog (planning on 46t chainring, 17t rear cog, and 165mm crank arms), I will need to get some wheels built by my LBS - I am leaning toward white Velocity Deep Vs with machined sidewalls. I don't know what hubs to use, though. I guess I will go with what they suggest for hubs.
Other than that, I'll need a stem, bullhorn bars, and a front brake. But first I need help with the drivetrain. Your advice is much appreciated.