I couldn't have said it better.
Kirk Albers Upper Arlington, OH
'52 Hobbs Track '70's Falcon Track Jelly Belly - PoolGel Professional Cycling Team
> We fit people all the time in my store using the olde timie "Fit Kit"
> system
> and my 30 + years of messing with position and fit....my (most recent)
> opinion
> is that seat tube height certainly counts to a degree but it is not the
> critical issue in sizing a bike.
>
> Most people, old or young, can easily accommodate their seat tube size
> ranging at least an inch or a few centimeters in either direction.
> Obviously
> standover is important as the bike becomes larger for.. ahem...
> comfortable
> clearance. But to say a bike should have 1/2" or 4" clearance really
> doesn't say much
> about the bike's proper fit except in the most general and secondary
> sense.
>
> That old 9" or 10 " less than inseam theory is OK, but has not much to do
> with ride-all-day comfort and efficiency.
>
> Of course, if you want the stem high and the seat level with the bars (!),
> then a taller frame makes sense. One person's geeky look is another's
> Nirvana.
> Once it gets so high, you may as well ride an off topic bike (mountain
> bike.)
>
> But in my not-so-humble opinion, the BIG deal is the top tube and stem
> combo
> measurement. Normally as stock geometry bikes get taller (larger sized)
> they
> also stretch in the top tube dimension. This can lead a disaster for that
> rider
> who wants that big bike in order to have higher bars.
>
> I personally feel that a relatively normally configured persons (not
> extremely long legs or torso for their height) should have a stem in the
> range of 9 cm
> to 11.5 cm for best handling and weight distribution over the front end of
> the bike. If a shorter or longer stem has to be used, it compromises the
> "system" of bike & body. The Fit Kit system has a pretty useful chart
> based upon a
> database that proscribes a certain "cockpit" overall length (top tube +
> stem)
> that works pretty well.
>
> Other systems use subjective decisions relative to "flexibility" and such
> that make it more guesswork IMO. Really good guys with years of experience
> (example: Ted Ernst) and a well honed eye, use none of this... They just
> study you
> on the bike and know whether you are well positioned.
>
> Anyway, if we want the stem length to fall in this "sweet spot", it means
> that the top tube length has huge importance. A person who must have a
> 54-55 cm
> top tube simply could NEVER be fit properly to a bike with a 58 cm top
> tube.
> It's interesting to me that few custom & high end bike manufacturers don't
> want
> to talk about top tube lengths.
>
> My advice? If you don't live near cycles de ORO or Ted Ernst (and other
> list
> member s who are aces at this stuff) find a long time Fit Kit trained shop
> or
> someone who has raced or ridden extensively and fit people since... 1983
> at
> least! (see the CR time thingie applies again.) Sadly that eliminates the
> triathlon - fashion plate - boutique services who just got back from a fit
> school
> somewhere. I have seen some of the worst crappola fits and positions
> proscribed
> by newbies...
>
> Dale Brown
> Greensboro, NC USA