Singlespeed & Fixed Gear - Bottom bracket too small?

I ordered a 115mm axle length BB from Nashbar and apparently it's too short for my bike since the 40-tooth chainring strikes the chainstay when I tighten it onto the axle. Is this a problem FG/SS riders have to deal with considering that the inner (and only) chainring is always bigger than when in a double or triple config? Am I doing something wrong or do I need a bigger BB because I've been looking for longer ones and they are hard to come by. Thanks.

it's not clear from your post, but are you putting your chainring on the inside of a double crankarm? because you could always try it on the outside instead. if you have track-specific (or some other kind of single-ring) crankarms it's surprising that 115mm is too short. are you putting a spindle for 68 mm shells into an italian 70 mm shell?

the other day i looked through a bin full of spindles at my lbs (for something short, naturally) and it was overflowing with 125 mm and above. you ought to be able to find something long enough.

It's not the size of the bottom bracket that matters; it's how you use it.

(OK, actually, that's not true at all.)

I put it on the outside of the arms but when I did that (after it not working on the inside) the bolts now scrape. It's not track specific so maybe that's my problem. 68mm by the way.

I put it on the outside of the arms but when I did that (after it not working on the inside) the bolts now scrape. It's not track specific so maybe that's my problem. 68mm by the way.

the bolts scrape! sounds like you need some short stack/chainring bolts.