In article ,
Artoi wrote:

In article ,
"Phil Holman" piholmanc@yourservice wrote:

"Artoi" wrote in message
...
With Paris-Roubaix, everyone's talking about the value of "relaxed"
frame geometry again, specifically the long head tube and the benefits
they bring.

My question is, what ride differences are there b/n a frame with a
longer head tube and a regular road frame that has more spacers
inserted
below the stem, thereby achieving a longer virtual head tube?

I've asked this question a number of times elsewhere and no one seemed
to be able to answer it directly.
--
I've never ridden cobbles very far but for normal road riding a longer
head tube will result in a frame that is torsionally softer. Think of a
twisted frame with the top tube and down tube out of plane. A shorter
head tube is torsionally stiffer than a long head tube and will resist
this kind of flex.

The closer the top tube is to the down tube where they connect to the
head tube, the stiffer the frame (all other things being equal). Adding
spacers will achieve a taller geometry without affecting frame flex and
handling.

The worst affect of torsional flexing is in the handling of the bike
where the wheels go out of alignment (head tube out of plane with seat
tube) and the bike does not track well.

This makes sense. So in other words, what people/companies refers to as
"relaxed geometry" is actually one that is a torsionally less stiff
frame. Then the issue here is, why would it be considered to be more
comfortable? By comfortable I would have assumed its more vertically
compliant. Frames in this category include Giant's OCR range,
Specialized Roubaix range etc.

A frame fit for long rough rides has very long chain
stays, and 70 degree head tube angle. The fork has a large
offset with the offset residing in a curve near the tips.
The fork blades are thick at the crown and gradually
taper to very thin at the tips.

--
Michael Press