Originally Posted by
Metacortex
In that case either the factory drawing geometry is wrong (unlikely) or a combination of tolerance stack, geometry variations due to frame size differences (geometry varies slightly in sizes other than on the official drawing) and finally measurement accuracy all contributed to your 0.7° measurement. I would still consider that a horizontal top tube even if it was possibly built or measured slightly different from what was intended.
Since the HTA and STA are pretty much spot on the angles on the drawing measured relative to the dropout baseline, and it's a custom frame built for me, the geometry on the drawing should be reflected in the frame since it was designed around me and in my size. I was pretty careful with my measurements, and the axle standoff fixtures have identical axle hole heights within a fraction of a millimeter.
I have several other frames with "horizontal" top tubes that I'll check. A 0.7° slope in the TT could throw off the actual HTA and STA by that much if they are measured relative to the top tube.