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View Full Version : How do you measure the geometry of a bike?


handsomerob
02-13-2008, 02:23 PM
To me the only precise measurement I know is the head tube length, that is a no brainer. But other measurements seem more fuzzy.

I have read about two ways to do Center to Top of seat tube measurements.

1.) Center of the bottom bracket to the top of the seat tube (with extention above top tube if applicable) or

2.) Center of the bottom bracket to the point on the seat tube where the top of the top tube intersects.

As far as Center to Center of the seat tube measurements... Do you measure from the Center of the bottom bracket to the point in the seat tube along the midline of the top tube? If so, the measurement between two bikes with the same standover and BB drop could differ if one has an oversized top tube. Is there anything to account for that?

For instance, Waterford uses a CTT minus 1.4cm to come up with their CTC of the seat tube.

In measuring the top tube, I would assume you measure between the center of the seat tube to the center of the head tube? If so, do you do it along the midline of the top tube? Does anyone measure from the center of the seat tube opening to the head tube opening?

Any help on what is closest to "standard"?

Thanks.

p.s. any clue as to how to adapt this to compact frames would be nice to. :rolleyes:

swoop
02-13-2008, 03:38 PM
looking forward to see your handmade bikes at NAHBS next year.

DarrenCT
02-13-2008, 03:41 PM
looking forward to see your handmade bikes at NAHBS next year.


did handsome rob get "the book" also?

swoop
02-13-2008, 03:43 PM
http://www.bikeschool.com/


is there a football team?

DarrenCT
02-13-2008, 03:51 PM
http://www.bikeschool.com/


is there a football team?

im signing up.

anyone interested in a frameset PM me. $669 deposit required. it shouldnt take me too long to figure it out.

ps: does home depot sell some bike making tools?

brians647
02-13-2008, 04:35 PM
im signing up.

anyone interested in a frameset PM me. $669 deposit required. it shouldnt take me too long to figure it out.

ps: does home depot sell some bike making tools?

Soldering iron - check
super glue - check
protractors to get yer angles right - check
duct tape - check

yeah, I think you're all set.

rwsaunders
02-13-2008, 04:51 PM
From the pages of the Master:

http://sheldonbrown.com/frame-sizing.html