Originally Posted by
1jacktripper
Hi,
Not sure if this is going to come out right, but I'd greatly appreciate any help. Also, I am wondering if I'm posting on the wrong sub-forum here, so much apologies if that is the case.
I currently have a compact frame with the measurements as attached, and it fits me really well, but I am wondering if such measurements would translate to the 49cm measurement (for traditional/horizontal toptube geometry) in the second page of the attachment.
If not the 49cm, maybe the 50cm?
Or is it not as easy as I'm making it out to be?
Thanks much!
Maybe this will help.
For the drawing on page 1 of your attachment, it appears the manufacturer is using the intersection of the top tube and the head tube (instead of the top of the handlebar stem) as the datum for determining the location to measure horizontally to the extended seat tube centerline to derive the virtual frame size.
I've marked up your drawing, and using a Gerber Variable Scale, measured what would be the center-to-center dimension of the seat tube (from the center of the bottom bracket shell to the intersection of the center of the virtual horizontal top tube and the center of a virtual extended seat tube. That dimension is 51.8cm.
If you used the top of the handlebar stem as the datum, the intersection of a virtual horizontal top tube with the centerline of an extended virtual seat tube would be 60cm.
If you look at the drawing, you'll see that this manufacturer drew the virtual top tube c-to-c measurement as 534mm, or 53.4cm, and that he used the head tube/top tube intersection for the datum.
