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2009-05-20 4:29 PM
in reply to: #2159718


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Subject: RE: The 20 mph barrier
The power to sustain a certain average speed does go up exponentially as the speed increases because of the the wind resistance against the cross sectional area of the rider and the bike. The figures I remember from some studies I read (I may be off a little so somebody make correct me if I amn wrong) that it takes around 160 or so watts to overcome the wind resistance at 18 mph. It takes around 200 watts to overcome the wind resistance at 20 mph. and it goes up from there. (22 mph/ 240 watts, etc)

As an athlete gets into reasonably good shape they can develop the capability to sustain 160 watts fairly qucikly. It takes a significant amout of additiinal training effort to be able to sustain 200 watts for any length of time. So the ability to sustained 20 mph for a long distance does reflect a significant improvement in your fitness. Going faster requires additional effort in improving your fitness. The amount of watts needed to sustain a certain speed is helped by improved aerodynamics to a small degree, but it comes down to what the engine can put out.

It simply gets harder and harder to go a little bit faster


2009-05-20 4:30 PM
in reply to: #2159718

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2009-05-20 4:31 PM
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2009-05-20 5:35 PM
in reply to: #2164353

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Subject: RE: The 20 mph barrier
browncd - 2009-05-20 3:29 PM
It simply gets harder and harder to go a little bit faster

Isn't this sentence equivalent to saying it takes exponentially more power? If the relationship were linear, increasing speed from 20-21 (+5%) would require the same percentage increase in power as is needed to go from 27.0 to 28.35 (+5%). Maybe that's true, I don't know. I just try to ride faster.
2009-05-20 8:07 PM
in reply to: #2159718

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Subject: RE: The 20 mph barrier
I'm still pondering whether not too hard is easier than not too easy.  Add to that the exponential part, now I really have a headache.

The final question is did we come even close to answering jimmb's question?
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