|Ryan Atkins atop his Steelwool in a pretty serious stage race.|
Humans tire; the question is: how fast? Heine discusses his findings: stiffer and lighter bikes are not faster by virtue of these factors. Rather, they seem to fatigue the rider sooner (due to lack of yielding to the power input), reducing the overall power available for propulsion. Heine thus tacitly references planing. The titanium bike in his experiment does not harmonize with his body's pedaling rhythm, but instead loads his legs with lactic acid prematurely. He is not able to produce as much power on the lighter, stiffer bike. This is thus a slower bike than its heavier steel counterpart.
One might blame perceptual bias, but I suspect Heine's protocols are sound. Heine and his co-tester, Mark, ride steel bikes a lot. They are attuned to the rhythm and resonance of 'flexy fliers.' They know how to work with them. The both believe they are fast bikes, and prove it by riding them fast. On stiffer bikes they are less efficient. At the same time, riders who have grown up riding stiff bikes believe they are faster. These riders are attuned to the resonance of stiff bikes, and feel slower on bikes that yield more to their input. Feeling slower can mean you are slower; the rider's perception of speed versus effort can either enhance or diminish one's power output. That is, if you feel like a hero, you can eke out more power. In contrast, if you feel like a 'zero,' access to your power will be diminished; you will undermine your ability. Cue the excuses.
In the final analysis, I would contend that the fastest bike for a given rider is that which harmonizes with the rider's belief and ability. PRO racers probably really are faster on ultra stiff bikes than they would be on lively steel rigs (it would be fascinating to involve PRO racers in the same experiment Heine undertook).
Rando masters like Jan Heine probably really are faster on flexy, heavier bikes. When you get down to the bottom of the matter, there is no one set of design parameters that is ideal for ALL riders. A great bike is one that the rider feels comfortable and fast on, regardless of how that is accomplished. If you want to change it up, you are going to have to be willing to take the time to get intimate with a new platform in order to get the most from it.
This said, 23mm tires really are slower than 25s on the road. ;)