if the slot behind the seat tube tapers in at the top, its been messed with,
in the last 11 years, by prior mechanics fitting an undersized seatpost, perhaps..
straight gage seat tube, wall thickness is constant, then it may be a 26.8.
27.2 is commonly fitted in a single butted tube wall thickness less at the top,
more at the bottom .. main tubes DB, so thinner wall in the center.
OD remains the same.
Last edited by fietsbob; 03-22-12 at 02:18 PM.