Re: [CR]Old racing bike geometry

(Example: Component Manufacturers:Chater-Lea)

Date: Tue, 01 Feb 2005 09:03:54 -0800
From: "Chuck Schmidt" <chuckschmidt@earthlink.net>
To: classicrendezvous@bikelist.org
Subject: Re: [CR]Old racing bike geometry
References: <a05210633be2469e73407@[68.167.191.8]> <00ef01c507f6$053250e0$0b00a8c0@DXROOM>


What I was really hoping for here was that some of you would go to the trouble of measuring your own bikes (accurately) and post the results to the CR list so we could build up a data base.

Anyone want to share?

Chuck Schmidt South Pasadena, Southern California

Angel Garcia wrote:
>
> Reminder: many Colnago rider's geometries are here:
> http://www.colnagonews.com/prova2/storia/geometrie/giannimotta.php see rider
> list left side.
>
> Angel Garcia
> Long Valley, NJ
>
> > From Claude Genzling's book (all measurements in mm, center-to-center):
> >
> > F. Coppi's bike exhibited in 1977:
> >
> > Seat tube: 582
> > Top tube: 565
> > Seat angle: 72.2
> > Head angle: 72
> > Fork offset: 50
> > Trail: 58
> > Front center: 600
> > Chainstays: 432
> >
> > Note that the trail figure given would require a wheel diameter of
> > 707 mm - way larger than even a Clement Del Mundo sew-up (which
> > measures 30 mm in width and 690 mm in diameter)
> >
> > F. Coppi's bike from an old photo:
> >
> > Seat tube: 570
> > Top tube: 570
> > Seat angle: 72.6
> > Head angle: 73
> > Fork offset: 50
> > Trail: 52
> > Front center: 600
> > Chainstays: 440
> >
> > _IF_ these are correct, they indicate more "modern" geometries than
> > those on Chuck's bikes. (The photos of Coppi's bikes clearly show
> > less fork offset than many contemporary machines, so even if the
> > measurements aren't 100%, they indicate a trend.)
> >
> > Finally, here is one I have measured:
> >
> > Learco Guerra, ca. 1950s, Campagnolog Cambio Corsa:
> >
> > Seat tube: 586
> > Top tube: 572
> > Seat angle: 71.5
> > Head angle: 72.5
> > Top tube: level
> > Fork offset: 57
> > Trail: 49
> > Front center: 603
> > Chainstays: 420-450 (adjustable)
> > Wheelbase: 1010-1040
> > BB drop: 77
> > Wheel diameter (Del Mundo 30 mm sew-ups): 690
> >
> > When I measured the trail, it was closer to 40 mm, so it is possible
> > that the fork offset is more than the 57 mm measured. Overall, I have
> > reasonable confidence in the measurements above, +/- 5 mm and 0.5
> > degrees. (Measuring trail is almost impossible, as you are projecting
> > the head tube way out, and half a degree off will result in great
> > changes down there!)
> >
> > For an upcoming article in Vintage Bicycle Quarterly, with a friend,
> > we measured more than a dozen old machines. Some interesting facts
> > appeared - some of the old bikes have very little trail (like Chuck's
> > measurements indicated as well), yet handle very stably. Working on a
> > hypothesis that explains why... all in the next VBQ.
> > --
> > Jan Heine, Seattle
> > Editor/Publisher
> > Vintage Bicycle Quarterly
> > c/o Il Vecchio Bicycles
> > 140 Lakeside Ave, Ste. C
> > Seattle WA 98122
> > http://www.mindspring.com/~heine/bikesite/bikesite/