Originally Posted by
Mike Mills
I could be wrong, but I think stiffness a racer is after is the the out of plane bending stiffness "below the lines". One "line" being the line between the bottom of the head tube and the rear axle. The other "line" is from the head tube to the front axle. These are the portions frame which would flex under load and tend to sap energy.
It is also important to have some in plane compliance, to soften the ride.
You'd also want a low hysteresis material so it will spring back after flexing. I would also bet hysteresis can be adversely affected by poor workmanship.
If the seat tube flexes a little, I'm not sure it matters in terms of energy transmission.
bingo!
one must always consider handling & road adhesion factors. the driveline & steering must be held locationally stable to provide precision,consistancy & efficiency but the very same tube structures must also provide suspension travel & shock absorbtion for comfort & road contact. that was my point of contention back in my first response to this thread-
"to me, the real question is whether or not all the added stiffness in a compact design is necessarily consistantly beneficial and without trade-offs . in my experiences, the thorough, well-considered, goal-oriented implementation of any given design philosophy is the real key to any superior and satisfying result."