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| Patrick, Salsa, I agree with you, but my query is a little more advanced than that. What you are talking about is "kinematics": the science of time and speed; it doesn't consider the actual forces. Yes, I am aware that when you go 4 kph one way and 6 kph on the other way, your average isn't 5 kph, but only 4.8 kph. If it were 1 and 6, the average is 1.7142...
What I was asking was in the domain of kinetics, which deals with time, speed and forces.
Can anyone explain what is happening when a guy is going 50 kph and then has a tailwind of 75 kph? In such cases is it better to have an upright bike than a racing bike becos you can then get more "push" from the back with a larger surface exposed? | |
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There are a lot more forces at play. As far as I know rolling resistance and rotational resistance at the bearings increases with speed too, so while not in the same league as wind resistance they play a role.
The other thing you have to consider is that a rider is not a machine, just because someone can develop 300W in one position it does not mean that they can develop it in the optimum aerodynamic position. This is why riders spend time in the wind tunnel, not to get the best aerodynamic position but to get the one that allows them to produce the best balance between power output at threshold and wind resistance.
A flat back actually helps cardiac output and therefore O
2 uptake, so there may be a case for keeping a tucked position even if it was a pure tailwind course. Of course this has to be weighed up against keeping the chest open to let O
2 in in the first place.
Also, if there really was a time trial with 75km/h winds I think all this would be academic. There would be cross winds somewhere on the course, and a time trial bike would be nearly impossible to ride in this kind of cross wind.