Re: [CR]30's Bike Geometries


From: freesound@comcast.net
To: Jerome & Elizabeth Moos <jerrymoos@sbcglobal.net>, Jan Heine <heine94@earthlink.net>, Mitchell Gass <mitchell@gassworks.com>, classicrendezvous@bikelist.org
Subject: Re: [CR]30's Bike Geometries
Date: Fri, 15 Jun 2007 22:29:50 +0000


Jerry,

I have a post in this thread in which I estimate the rake and trail of this frame based on the photo. I think the trail is in the 50 to 60 mm range, and the rake is around 80mm. That is in the same ballpark as modern frames. The head tube angle is low, aroudn 67 degrees, but as you point out the rake is large to compensate.

In the Chuck Schmidt post containing older bike geometries, those trails ranged from in teh 30s mm to nearly 60 mm. Even if it was 60 it woldn't be a lot longer than most modern bikes. So I think I agree with you to be skeptical about Jan Heine's claim that pre-war bikes had super-long trail as any kind of general rule.

Ken Freeman


-------------- Original message --------------
From: Jerome & Elizabeth Moos

> Were Pre-War bikes really super-long trail? If I understand the concept

\r?\n> correctly, shallow head angles does increase trail. But doesn't a long fork

\r?\n> rake decrease trail? Pre-war bikes typically had long fork rake as well. So

\r?\n> was the net result really that drastically different from modern bikes with

\r?\n> steeper head angle, but also less fork rake?

\r?\n>

\r?\n> Regards,

\r?\n>

\r?\n> Jerry Moos

\r?\n> Big Spring, TX

\r?\n>

\r?\n> Jan Heine wrote:

\r?\n> At 10:37 PM -0700 6/14/07, Mitchell Gass wrote:

\r?\n> >It's striking how different the geometries of 1930's road bikes like

\r?\n> >the Legnano currently on eBay

\r?\n> >

\r?\n> >

\r?\n> >http://s211.photobucket.com/albums/bb148/cazpiroz/?action=view┬Ąt=001.jpg

\r?\n> >

\r?\n> >are from modern bicycles. What was gained - and what was lost - in the change?

\r?\n> >

\r?\n> >Mitchell Gass

\r?\n> >Berkeley, CA USA

\r?\n>

\r?\n> It is interesting how quickly bike geometries evolved in the late

\r?\n> 1930s. By 1939, many bikes had geometries that were very similar to

\r?\n> modern bikes. The sloping top tubes also went out of fashion, and

\r?\n> most makers preferred level top tubes. I wonder why they did the

\r?\n> sloping top tubes, because most racers had their handlebars much

\r?\n> higher than those on that Legnano. Also, I suspect the Legnano was

\r?\n> designed for much wider tires... look at those clearances!

\r?\n>

\r?\n> Even after the war, when roads were much worse than before in many

\r?\n> parts of Europe, builders did not go back to the super-slack head

\r?\n> angles and super-long trail. From my experience riding bikes like the

\r?\n> Legnano, they just don't handle as well as later machines. So I think

\r?\n> there was some real progress, where builders finally did figure out

\r?\n> the front-end geometry.

\r?\n>

\r?\n> After the war, things were refined further, usually by steepening the

\r?\n> head angle a bit more, until 73 degrees or thereabouts became

\r?\n> standard.

\r?\n>

\r?\n> Coincidentally, handlebar widths decreased tremendously as geometries

\r?\n> changed. In the 1920s, it was common to have 50 or more cm wide

\r?\n> handlebars. On those geometries, the added leverage probably is

\r?\n> useful to fight the wheel flop. By 1939, handlebars rarely were even

\r?\n> 40 cm wide, because you did not need to wrestle with the bike any

\r?\n> longer. Of course, during the same time, the material of the bars

\r?\n> changed in many cases from steel to aluminum, so one could argue that

\r?\n> is was a fear of breakage that made manufacturers weary of extra-wide

\r?\n> bars. But even steel bars became narrower. (Or was it that because of

\r?\n> the war and malnutrition, riders' shoulder widths decreased?)

\r?\n>

\r?\n> The 1930s altogether were a time of great change in racing bike

\r?\n> design. This is a simplification, but effectively, a 1929 bike is

\r?\n> closer to a 1900 bike than it is to a 1939 bike. And a 1939 bike is

\r?\n> closer to a 1985 bike than to a 1929 bike. Whether you look at

\r?\n> geometries, weight, materials... it all changed in the early 1930s.

\r?\n>

\r?\n> I once rode a 1939 Oscar Egg that was very light (I recall 21 lbs.)

\r?\n> and spirited. I wouldn't mind racing that bike today on a flat or

\r?\n> moderately hilly course. The Super Champion changer worked well, but

\r?\n> the gear range was rather limited...

\r?\n> --

\r?\n> Jan Heine

\r?\n> Editor

\r?\n> Bicycle Quarterly

\r?\n> 140 Lakeside Ave #C

\r?\n> Seattle WA 98122

\r?\n> http://www.bikequarterly.com