Elisa Francesca Roselli said:I keep having the impression that my new bike is too big for me. The vendor insists that for my
1.72 meters, the recommended frame size is 56 inches. A competing vendor suggests that a heavy
person like myself may be happier on one size down, a 53 inch frame, since that would make it
easier to keep a foot on the ground (I cannot start and stop or ride standing).
I think you mean 56 and 53 cm. Frame size is specified by seat tube length. Different manufacturers
use different methods of making this measurement. It is always measured FROM the center of the
bottom bracket. It is measured along the seat tube TO either the top of the seat tube, the top of
the top tube, or the center of the top tube. If the frame has a sloping top tube, it may be measured
to an imaginary point where the top tube would intersect the seat tube IF it were level. As you can
see, it's not easy to compare sizes between different bikes and especially different manufacturers.
In addition, there's more to "frame size" than just the seat tube length. Top tube length is
probably more important as it will determine how stretched out you are on the bike.
Height is not a very accurate way to choose a frame size. For determining seat tube length, your leg
length or "inseam" is the critical parameter. Top tube length should be chosen based on torso and
arm length (as well as personal preferences and type of riding).
If the saddle seems too high on the 56 cm frame, maybe you can lower it a little. Then when you
become comfortable starting and stopping, you could raise it up. Having the saddle too low doesn't
allow you to extend your leg properly. That can limit your power and can cause knee pain.
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Art Harris