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Frame Size
From WikiPedalia
Frame size generally refers to a measurement of the seat tube. This is measured from the center of the bottom bracket to somewhere near the top of the seat tube. Unfortunately, manufacturers disagree about where to figure the top of the seat tube, so the same frame may have as many as 8 different size numbers attached to it, depending on the manufacturer!
- Frame size may be measured in inches or centimeters.
- Some manufacturers measure "center-to-center ", i.e. to the intersection of the center of the top tube with the seat tube.
- Some measure to the intersection of the top of the top tube.
- Some measure to the top of the seat tube (which protrudes a variable amount above the top tube.)
- Some measure, on bikes with a sloping top tube, to where the seat tube would end up if the top tube didn't slope!
- A further complication is that different bicycles have different-height bottom brackets, so the stand-over height of two different frames may differ, even though both are 58cm center-to-center!
If you ask a bike salesperson "what size frame do I need", and get back a number as an answer, without specifying a particular make and model group, you are not getting good advice.
In my opinion, seat-tube length is not the most important frame dimension anyway. See my article on Frame Sizing for the details.
