Framebuilders - Standard Geometries

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View Full Version : Standard Geometries


jr-14
10-22-09, 04:37 AM
I'm looking for some geometry benchmarks for different frame types. A starting point that I can modify for individual people, for the type of frame they want.


old and new
10-22-09, 09:57 AM
You're currently building frames? I don't but no stranger to frame geometry I'll sight some examples. Every bicycles currently sold lists full specs.; angles , dimensions as per core size. It's inportant to note that most Italian & custom builders use C to C measurements for seat tubes; most other Co.s use Center to Top; all use C to C for Top tubes. An American designed bike for instance that measures 56 X 56cm for instance is not as "square" as one would think, on account of the top tube's diameter skews the measurement as it's about an inch in OD, resulting in a half inch disparity resulting in a longer TT than ST, think about it.
Although Gios is viewed to be a radically short wheel based bike, it's more traditional than one might expect. Race bikes 20 yrs. ago & moreso 30 yrs. ago were similar.
Excell Sports sell them, has a chart as well as text. Start with 55cm & 56cm sizes in these and other bikes, more definative. Gios & others aren't so square, Race bikes rarely were. A 74 deg. ST angle with a 73.5 to 74 HT angle was a classic type. All this irrespective of fork curvature resulting in effective rake as well as wheelbase.
Read the Wrench Science site; they've various Italian companies listing frame imfo.
Click on Boutique and view the NeoPrimato DeRosa (squarish) & Colago Master Lite which is meas. Center to TOP (atypiical) for Italian, while the Geom. is classic with very intense specs. If you view Cinellis (steel) bikes on line, you'll notice differences.
No two Italian builders were identical. Look at Pegoretti too, his bikes are longer.
Gitane's main site www.gitane.com (http://www.gitane.com) is more historical than commercial. Tables are listed. It's interesting to note that LeMond started on Gitanes, eventually created his own company and ironically uses "opposite" frame geometry. Lemond used slack seat tube angles with steeper HT angles, shorter than long W.B. resulting in very long top tubes. Do try to find specs. on LeMond bikes, especially the later ones ( 97 up)
Co.s based in the US list everything, steel ones you'll see are decidedly square. Investigate popular custom builders. Look at catalogue scans of Fuji & Miyata etc.
I just wrote of the not so obvious, the classic types that often are misunderstood.
All of this should be obvious to you now if it wasn't already.

jr-14
10-22-09, 02:01 PM
Thanks for all the great links, and references!


NoReg
10-22-09, 02:16 PM
I tend to worry about the accuracy of those frame charts. Sometimes the numbers are out for marketing reasons. Also, there are subtle differences between different makers that may have no rational explanation. The various makers may have rational reasons, but there is little basis for sellecting among them unless you are already further down the road than you describe.

Anyway, try this:

http://www.timpaterek.com/paterek.pdf

page 8

To get some baseline info that will be real to you, measure your own bikes, compare them to charts. Develop a familiarity with the numbers.

jr-14
10-23-09, 04:35 AM
Thats what I've been doing, but I was just hoping for a cheat sheet. I'll just make my own.

Thanks folks!