At 07:06 PM 9/4/04 -0400, Jeff Noakes wrote:
>If you're using handlebars similar to the stock unit on the bicycle, how
>long a stem extension have you tried using? I have some French handlebars
>that are takeoffs from a mid-80s Peugeot and are essentially flat bars with
>their ends swept back at almost 90 degrees for grips and brake levers. I
>tried fitting them to a Mercier road bike beater, with the bars a couple of
>centimetres below saddle level. The handling became *very* twitchy. The
>extension on the stock stem was fairly short (~6-7cm) and I noticed that
>when my hands were on the grips they were further back than the headset --
>in other words, a line drawn between both hands would pass behind the axis
>of rotation for the stem. In contrast, when the bike was fitted with a
>similar stem and drop handlebars, my hands were always further forward than
>this and the bike handled quite well. I wouldn't be surprised if the
>rearward positioning of my hands on the flat "town" bars, coupled with road
>bike geometry and a change in weight distribution because of my changed
>upper body position on the bike, caused the twitchy handling.
>
>While trying to diagnose the problem, I compared that "town bars" setup
>with photographs of roughly comparable handlebars on *much* nicer French
>bikes put together by people who *really* knew what they were doing.
>Looking at a Rene Herse Gentleman on Chuck Schmidt's website, for instance:
>
><http://www.velo-retro.com/vr2.html>
>
>more specifically:
>
><http://www.velo-retro.com/VRendez.jpgs/MattHerse.jpg>
>
>I noticed that the stem has a fair bit of extension, placing the handgrips
>largely in front of the headset. This may have been to provide the desired
>handling, to fit the owner, or probably both.
>
>Of course, if I'm talking complete rubbish about stems, handlebars, frame
>geometry, and handling here, I'd be more than happy to be corrected.
Roadsters, with their laid back angles and grips higher than the seat, steer just fine with the hands behind the steering axis. But with steeper angles and lower bars you end up pushing down and somewhat forward. Most people will find this destabilizing if the hands are behind of the steering axis.
Similarly, on recumbents you pull back on the grips, so they are more
stable with hands well behind the steering axis.
> >What brand of fenders are on the bike in the link that Steven Barner
> >included in his post?
>
>It's a WAG on my part, but they look like they could be Bluemels Airweights:
I'm 99.99% certain they are Esge Chromoplastic.
Mark Stonich;
BikeSmith Design & Fabrication LLC
http://bikesmithdesign.com