TECHNOLOGY STORIES BIKE INFO, GEOMETRY ... - Vintage Trek

Good fit defined
A rider pedaling a bicycle touches the bike in three
places; pedals, saddle, and handlebars. For the bike
to fit properly, these three points must interface with
your body in a comfortable and functional way. In other
words, if the saddle, pedals (and shoes), and handlebars
(plus grips and controls) do not fit your feet, hands and
seat, the bike won’t work its best for you.
The three points of contact must be oriented correctly
for you to benefit. Properly oriented, your muscles will
work at their optimum. No muscles, ligaments, or tendons
will be strained. Aerodynamic drag will be at a
minimum.
In addition to the relatively simple task of accommodating
your body for comfort, the bike should ride
better. Your center of mass should be positioned over the
bike to accentuate your pedaling power while also balancing
you over the wheels for the best bike handling.
Put more simply, good fit results in your feeling completely
relaxed on the bike over long periods of time. If
your bike fits well, you should not feel like you need to
squirm around, nor should you have excess tension in
your shoulders, arms, or anywhere else. Basically, you
should be comfortable, first and foremost.
How performance effects fit
The higher the performance level of your riding, the
greater the forces applied to the bike, and thus to you.
Forceful riders press harder on the pedals. They corner
harder, and when riding off road their extra speed generates
higher forces when they hit bumps. The forces
applied to you on the bike are the result of a Newtonian
law that states all actions have equal and opposite reactions.
When you are riding, higher forces demand better
fitting if comfort is to be maintained.
However, in some cases greater forces may be found
when your are riding less forcefully. If you are not
pressing firmly on the pedals, you’re not lifted by the
pedals. As a result, the casual rider often applies their
entire body weight to the saddle.
Regardless of the level of your riding, our definition
of good fit holds true. Every rider should use the least
muscle energy possible to support themselves on the
bike, to stabilize themselves on the saddle, and to apply
power to the pedals. To be relaxed requires that you be
as comfortable as possible.
Fit info in this Tech Manual
On the specifications page for each bike model, we
have listed the Fit items for that model, including the
lengths, angles, or widths of the handlebar, stem, crank,
and seatpost.
Rider Height
In addition to the measurements of the hard parts, we
list Rider Height. This dimension is the median height
of the average rider who might fit this bike in an average
way, with its handlebars at their highest position.
That’s a lot of qualifiers, but the information can still be
valuable in helping you quickly fit a given model. Some
models do not include Rider Height, either because that
model offers too much fit adjustment to be defined, or
simply because it’s a one-size-fits-all. So here’s all those
qualifiers explained.
Median Height- Different bikes offer different ranges
of fit. Generally, the more bent over you are, the more
noticeable a poor fit. Most bikes fit a range of heights.
Trek 2002 Tech Manual
Bike Fit
Different bikes will have a different range. We have not
attempted to define how wide the fit spread is on a
given model; the variables are too many. Instead, we
have listed the median, or middle. In other words, if we
say a bike fits someone 70” tall it may fit someone from
69 to 71”, or possibly (depending on the model) with a
wider range from 67 to 73”.
Average rider- When we design or spec a bike, we
have a certain style of riding in mind. As an example,
when we spec a 8500, we’re expecting that the bike
will be either ridden by a racer, or someone who likes
to ride like a racer. That doesn’t mean you can’t ride
a 8500 on the bike path. But someone buying a 8500
exclusively for bike path riding isn’t riding in an average
way for that model, and will likely want to tune the
fit to their purposes.
Average Fit- We’ve studied a lot of riders over the
years, and we can draw some conclusions about the
way a bike fits the average person. But some folks
aren’t average. Those with specific preferences, injury,
or other abnormalities may require or prefer a nonaverage
fit. As examples, consider two people of the
same height but different weight. At 6’ tall, a 130
pound person will sit on a bike differently than someone
also 6’ tall who weighs 260. Incidentally, neither of
these folks would fit our definition of average.
Highest handlebar position- We made these fit estimations
with the stem at its highest point. With Ahead
stems, that means all the spacers were under the stem.
With quill stems, the handlebars reach their maximum
height with the stem pulled up to the minimum insertion
line. With adjustable stems, it’s calculated with
the stem at a 40 degree angle. Lowering the bars, or
changing the parts, changes the fit of the bike as well
as its Rider Height.
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