"Dave Thompson" wrote in
:

RP10128 wrote:
I need a bike with a top tube of about 50.5 cm. To get a top tube
of
that length, I need to get a frame that is one or two sizes too
small. That is, I would have to get a 49 cm. frame, whereas my
inseam
would indicate a 52 cm. frame. My LBS says that it doesn't matter
that the frame is so small, but this strikes me as being
counter-intuitive. Is the LBS right? Should I get the correct
size
frame and install a very short stem?
No, a short stem makes for a bike that doesn't handle as well as it
should. The primary measurement for a bike *is* the top tube. A
taller
seat post can make up for the frame size otherwise. Also, as you
get
more fit and in better condition, you will have a tendency to want
to
get *longer*, that is be more stretched out.

How did you arrive at the 50.5 dimension for the top tube?




In two ways. First, I have been riding my current bike (a 52 cm.
Trek) with the saddle slid all the way forward, and with the nut that
secures the seat post clamp slid all the way forward. With the
saddle in that position, the distance from the mid point of the
saddle to the center of the head tube is about 50 cm. Second, I feel
that the top tube of my current bike (which has a top tube of 52.3
cm.) is about 2 cm. too long.