In a message dated 6/6/02 5:57:45 PM Pacific Daylight Time, Philcycles writes:
<< I know you're a builder too but if I build two bikes identical except for the curved stays on one and the ride the same I would argue the stays are a styling matter. I see no evidence of flexing at the BB-no cracked paint no cracks period. But this is clearly a religious matter so no matter what any of us say (and several builders on the list concur) you will still believe the back end is flexing. >>
Hi Phil,
I apologize if my first response was a little abrupt. If you want to discuss
the hypothesis, I propose this for sake of discussion, "bent" seat stays in
all cases:
Frame #1: Seat stays and chainstays, .1mm wall thickness, 16" long, steel
Frame #2: Sear stays and chainstays, 1mm wall thickness, 16" long, steel
Next, the same except 20" stay length.
This is admittedly an extreme comparison, but I believe we are talking a
matter of degree, not whether.
I would expect that the .1mm stays would allow a measurable flex compared to
a same pattern 1mm set of stays and that this would be greater with the
longer stays. I further expect this could be calculated in a similar manner
to the calculation that I did with a friend (physicist) about the power loss
due to frame deflection of a given measurement of deflection. The lighter
and/or longer the stays, the more noticeable the effect/deflection. As you
increase stay thickness, it is probably a geometrical relationship between
the ability to "feel" and/or measure it, i.e., a 1mm stay will probably not
be noticeably different from a .8mm stay, depending on length, yet it might
be quite noticeable compared to a .4 or .5mm stay. The crossover point
between noticeabilty/measureableness can probably be calculated but it IS
there. Whether it makes any practicable difference, depends. To call it a
marketing gimmick? It depends on the material, the thickness and the length.
It's not a straight forward simple thing.
Add to that, some people are better at "feeling" things that are pretty
subjective than others. I'm perhaps a little sensitive to it because I fall
into that accursed group. I give credence to those that can discuss "nuance
of feel" in a way that makes sense to me.
Paint is usually flexible up to the point of underlying metal failure or
"extreme" flex, so may not be an indicator in this instance.
Best regards,
Stevan Thomas