So Im putting together a Surly Steamroller and was going to re-use the bb from my old bike (shimano UN-54, no plastic) 110 mm. I also hope to re-use my shimano 600 (FC 6207) crankset with a white industries eno free wheel cog. Also im on a surly hub (not sure the make or the model, I picked up the hub probably in 2011-12) Unfortunately I have yet to put in my BB and I dont have the free wheel cog yet so measuring the chainline is bit tough. Does anyone know enough about these components to tell me if my chainline will be straight enough without respacing the axle or redishing? If its gonna be way off should I get a new BB or crankset (Id like a flip flop hub).
Cheers.

I know the UN-54, 110mm BB has a non-symmetrical spindle. Meaning, spindle lengths are unequal on either side. This may, or may not, mess up your chainline. I know it did for me. Good luck.

Any idea why that is? I recently bought a UN-55 and it's off center by 2mm.

The UN-54 isn't designed for a track bike. It's so the chainline will still be within tolerance (is that the right word?) for a 2 and 3 chainring crankset. If you're using a JIS crankset, Miche makes a 110mm BB (this is a pretty recent phenomenon--it seems everyone is still wrapping their heads around the fact that the newer Miche cranks are JIS and not ISO).

Miche Primato Track Pista Bottom Bracket 110mm English JIS [1913A00200000] - $29.00 Velomine.com : Worldwide Bicycle Shop, fixed gear track bike wheelsets campagnolo super record vintage bike

Is there much difference between the 54 UN55? I thought one was ENG and was was ITA thread but I could be wrong?

I had to find a JIS BB with ~110mm spindle (OK crank calls for 110.5) in Italian threading. My options were pretty limited once price was factored in. I went with the UN55 and it paired my 73 Bianchi with a new FSA Gimondi crank just fine but I do wonder about the chainline being exactly strait. I know, 99 problems.

I think the difference is in the material used for the retainer cup, on the non-drive side. The UN-54 has a plastic, while the UN-55 has an alloy cup.

I'd just get the correct bottom bracket to fit your frame/crankset. I would not go messing around with wheel dish or trying to use spacers to move the spindle side-to-side (why? I dunno, I'm just picky that way). Oddly, I went through a similar issue about six months ago and had half a dozen brand new BB's just laying around until I finally found one that worked. I ended up donating the unused (still new) BB's to a local non-profit bike shop.

Yes, it was a little costly, but very educational.

OH i think you are correct I do remember something like that now. I did notice that my spindles were slightly off, like SquidPuppet said. So far I haven't noticed any excessive noise or thrown a chain or anything. However, my Crank, chain, and freewheel are all 3/32 (greater margin of error) and visually it LOOKs strait. I've seen some that it took all of 3 seconds to know the chainline was way off.

Ah, that answers my question, thanks.

Actually, for this particular OLD oddball bike, the offset helped me get closer to a perfect chainline while keeping the Q factor as centered as possible.