[exue]

Got it, hope that helped! I'd be very interested to see what the analysis is for a bike and what the optimal human efficiency is like.

In my experience riding road/hybrid bikes vs. mountain bikes, the lower resistance tires reduce the effort even if the gearing is similar. I'm also guessing the human leg has a narrower efficiency range in terms of RPM and power produced, so bikes usually have 15+ gears.

Now that I think about it, the 'simplest' way to explain the curve is - the vehicle/powertrain variables determine the efficiency curve with ideal gearing e.g. a CVT. If you have a 4 speed transmission, you choose 4 optimal points and imagine a steeper efficiency fall off in between each point (4 flattened parabolas with vertices at the optimal points).

[taeric]

The wikipedia article covers it decently.[1] And, the tires definitely have the most obvious effect at getting up to speed. However, I know that my top speed is higher on my road bike than it is on my mountain bike of similar tire size. I have mostly attributed that to the gearing. (Simply put, I am peddling as fast as I can on the mountain bike and going slower than a modest peddle on the road bike.)

Mayhap I am wrong there, as well.

[1] http://en.wikipedia.org/wiki/Bicycle_gearing