Re: [CR]Rear racks on French camping bikes

(Example: Framebuilding)

In-Reply-To: <20050406040233.6476.qmail@web51110.mail.yahoo.com>
References: <20050406040233.6476.qmail@web51110.mail.yahoo.com>
Date: Wed, 6 Apr 2005 06:08:35 -0700
To: John Clay <jmedclay@yahoo.com>, classicrendezvous@bikelist.org
From: "Jan Heine" <heine93@earthlink.net>
Subject: Re: [CR]Rear racks on French camping bikes


In Rivendell Reader 25 or 26, I reported on my Alex Singer camping bike, which has both low-rider and standard racks. Even when loaded with more than 30 lbs. on the rear, rack flex was not a problem with either mounting location. If they flexed, I did not notice. (And I do notice the flex with much smaller loads on an aluminum Blackburn rack.)

Using the rear low-riders lowers the center of gravity, resulting in cornering that is superior to an unloaded bike. However, putting the load so far back means that shallow speed bumps and other relatively long-wave undulation result in the rear wheel unloading a lot at speed. It did not jump, but it felt like it was getting close. This does not happen with the panniers on the standard rear rack. (In both cases, I had a weight distribution of about 60% front and 40% rear, for a total load of 80+ lbs.)

Note that with a normal camping load, which is about half the one I used in the test, this behavior probably would be much less pronounced.

Nonetheless, I would suggest a rear low-rider for smooth roads, and a standard rack for unpaved trips.

I can see your concern with flex on the low-rider racks. As you say, any triangulation would have to go through the rear wheel. I think in the end, the tubes used are large enough in diameter and wall thickness to prevent excessive flex. The tubing is considerably larger than that for the handlebar bag support racks. When trying to flex the rack by hand, one notices that it is very stiff - much more so than the above-mentioned Blackburn standard rack. (A standard bicycle frame's main triangle isn't triangulated either, yet does not flex excessively.)

Also, from my experience, most of the flex on "standard" racks occurs in the adjustment parts, such as sliders, straps, etc. (Chain as strong as weakest link, etc.) A custom rack has none, making it an integral part of the frame.

Jan Heine, Seattle Editor/Publisher Vintage Bicycle Quarterly c/o Il Vecchio Bicycles 140 Lakeside Ave, Ste. C Seattle WA 98122 http://www.vintagebicyclepress.com
>Looking at the rear racks on French camping bikes and
>wonder if they are prone to flexing laterally. They
>sure look like there isn't much to prevent racking to
>the left and right.
>
>Is that an issue?
>What prevents that sort of motion? I can't envision
>any sort of triangulation or web section to address
>it.
>The connection to the mid point of the SS appears to
>be the tension member that keeps the rack from
>pivoting down and backwards - Does that work OK?
>They lower the CG but also move it aft - does that
>feel funny?
>I keep wondering if all in all this sort of design is
>really superior to the more conventional designs of
>the present.
>
>Interested to know whachya'll think.
>
>John Clay
>Tallahassee, FL
>
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