Originally Posted by
rpenmanparker
Giant's seat tube measurement is actual seat tube, not effective seatube. So the slope of the top tube is not accounted for. To get a truer numerical size for a Giant racing frame add 4 cm to the seat tube number provided. So the Giant L is comparabel to a 57-58 in other brands.
Agreed. 53.5cm sounds like the actual seat tube length which is useless in compact frames. Giant should call the size by the top tube like some others do.