Quote:
Originally Posted by cachagua
Mmmm... so the frame springing back sums with your next pedal stroke, and the combined force moves you forward more than your pedal stroke would alone?
Maybe you could flesh that out a little bit? I'm not quite seeing it yet.
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No. I'm saying that the net force delivered should be the same, but delivered in different ways because the springy frame is storing the peak torques and delivering them later in the pedal stroke. Much like Biopace.
That said:
Quote:
Originally Posted by mt2u77
Rest assured, even the stiffest frame out there still deflects and acts like a spring. It's "spring constant" is just greater. It will still store and return just as much energy-- e.g. twice as much force to move it half the distance.
I don't see how more flex is better unless it somehow acts as a mental cue to help our pedal cycles stay on point, or indirectly as enabling some other attribute such as lighter weight, better aerodynamics, comfort, etc.
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There may be a point when the frame resists flex to such an extent that the asymmetric forces of pedaling overwhelm the system and go somewhere else that is energy wasting - like sidewall flex or a lateral loss of traction.
I really like climbing on my old Cannondale 3.0. The short, stiff stays delivered the peak force of my standing pedal stroke directly to forward motion. However, the bike tolerated sprinting uphill less than other bikes because the tires broke traction more easily if you weren't careful. So while it felt efficient, it limited when and how much power I could put through it without wasting it. My Merlin Extralight doesn't feel like it climbs with as much authority because it feels 'soft', but I would be shocked if I was actually expending more energy, and I know the tires don't break traction in the same circumstances as the Cannondale.
Just an illustration from my experience, not saying the above is definitive. We all like the way a stiff bike responds to input, but we don't have a somatic way to measure efficiency.
And that's ignoring the chainstays' role in distributing fatiguing bumps.