don't worry about what tubing it is on the frame, just do what you want to do to it and ride it.
For once +1.
531 isn't worth hunting for, its not that great-a-tubeset anyway, and as you now have a bike why not work with that and get a feel for riding fixed before splashing out too much?
For once +1.
531 isn't worth hunting for, its not that great-a-tubeset anyway, and as you now have a bike why not work with that and get a feel for riding fixed before splashing out too much?