[CR]Re: 50 cm frame

(Example: Production Builders:LeJeune)

To: classicrendezvous@bikelist.org
From: "Robert Schenker" <ris@schenkerdesign.com>
Date: Mon, 11 Dec 2006 11:07:11 -0800
Subject: [CR]Re: 50 cm frame

Before getting too far down the road on your quest for a better fit, be aware that there are a number of problems in designing small sizes (50cm and below). This leads to some very different geometries--much larger divergences than occur in larger sizes. Basically, it comes down to fitting two wheels into a smaller space. If everything is kept strictly proportional, not only would seat height shrink, but also reach to the bars, wheelbase, etc. However, this proves impossible since the wheel size isn't changing. So some approaches leave the wheelbase longer, or the top tube gets longer, or to avoid the latter, the head angle gets shallower and possibly the fork offset also increases. Sometimes the bottom bracket height is increased.

It's just not safe to generalize that a smaller frame size is the cure. Since I have personal experience (my wife is a small person) I've found that you really need to carefully look at the position your rider needs to achieve and then carefully look at the frame before you. Don't automatically discount the options of a short stem and/or not much seatpost sticking out. Other strategies I've used that have made a very workable bike out of an unlikely looking frame include considering crank length, Q-factor, over-spindle dimensions of pedals, and even the rail to surface dimensions of different saddles. Also worth looking at are the subtleties of different handlebars---some have longer brake reach than others, etc. One useful rule of thumb: the smaller the rider the less difference there will be between the height of the seat and bars to get the same sit position (back angle, arm reach, etc.).

Good luck, Bob Schenker Oakland, CA


> Date: Mon, 11 Dec 2006 01:30:05 -0500
> From: "Anthony Bier" <scratcheduprecord@hotmail.com>
> To: classicrendezvous@bikelist.org
> Subject: [CR]WTT or Buy 50cm touring frame
> Message-ID: <BAY131-F25A3F3717D79AE8396B287BAD00@phx.gbl>
> Content-Type: text/plain
> MIME-Version: 1.0
> Precedence: list
> Message: 14
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>
>
> Hello listers,
>
> I am looking for a frame for my Girlfriend that is more KOF than on
> topic because I would like a lugged steel cantilever boss equipped
> touring frame in a 50cm size. Her current 52cm is too large for her,
> she is too stretched out. I have several bikes I could trade including
> the 52cm Norco Magnum GT frame which this frame would replace, I also
> have a 52cm Trek 610 which is 531, a 49cm Bianchi Super, a 62cm
> Raleigh team Pro (workshop bike 1985) and a 1975 Jeunet 531, simplex
> DOs.
>
> Thanks
>
> Anthony Bier
>
> Vancouver, BC, Canada