...THIS is a downtube! Yes, I am building myself a track bike. Yes, it has a 44.5mm BMX downtube. No, there's no good reason for it, except that I'm using only orphan tubes for this and it seemed like it would *probably* be stiff enough. It will also feature some tandem chainstays that I bought on a whim (for cheap) and can't find a use for, as well as the horrible double taper seatstays I purchased by mistake and a toptube that I mis-mitered for Eszter's 29er... should be just as wacky as the 24" dirtjumper that I built from orphans that already lives at the track!