Correct way to measure a frame?

[dannywhiteley]

Been told a few different reference points so could I double check what measurement is correct for frame size?

Middle BB to top of seat post

or

Middle BB to seat post pin (top tube centre line)

Thanks,

 

[orange71]

will vary from manufacturer to manufacturer unfortunately. GT measures centre to centre, for example. Others go centre to top.

 

[FluffyChicken]

Frame Size
Centre of bottom bracket to Top of the seat-tube. (CTT)
OR
Centre of bottom bracket to Top of the toptube at the seatube (CT?)
OR
Centre of bottom bracket to Middle of the seat-tube/toptube interest (CTC)


1st one gives a in my opinion correct frame size, and regularly used
2nd one is not used much afaik
3rd one is also used by some and by certain manufacturers, though doesn't really give an indication of frame size as it would depend on the slop of the top tube.

BUT quote what the manufacturer of that frame would quote, if known. also mention how it was measured.


But often far more important is
Effective Top Tube length
Centre of headtube/toptube intersect to where centre of an imaginary horizontal line intersects the seattube line.

No point in quoting the actual top tube length normally.



... that's my opinion