daveornee said:
If everything else in the comparison of 700C to 650 wheels (including tires and tubes) are the same then:
1. ....
5. On normal pavement rolling resistance is higher
Not a really important factor. As it's explained on
http://sjscycles.com, smaller wheels means the tire is flattened under the rider's weight in a wider circle as opposed to a narrower oblong ellipse. The main difference is that a 650 wheel or an even smaller 26" wheel steers more easily than a 700c wheel. Minute difference, I should add.
There is another factor: a larger wheel rides smoother on obstacles such as cracks, potholes and the like. Ths has been an argument used by the proponents of "29-inch" MTB wheels (which are really 700c wheels with large tires).
Going up and going down
Climbing ability depends on muscular strength and muscle/weight ratio, whereas speed on the flats and especially on descents depends on air drag. A vey light person will be the last in descents.
Gearing vs wheel size
No difference once you adapt gearing. Or to give an example, 52/27 with a 27" wheel is the same as 52/26 with a 26" wheel (nominal sizes taken here for the sake of simplicity). Use
http://sheldonbrown.com/gears to compute gearings; the same development should give out the same ratio.
Crank size
That's where issues become more complex.
Physics 101 (yes, I even taught the course) would tell you that you have more power with 175-mm cranks than with 165-mm cranks. Specifically, if you apply a given force (say 100 N, which is roughly 22 lb) on the pedal, you will get 17.5 N-m torque vs 16.5 N-m, hence more pull on the chain, more force up the hill, etc.
However, biomecanics go against it and tell you that there is a relatively small range of effective position for the leg. So if you use 250-mm cranks (extreme, I know), there will be a very limited angle of the cranks under which you would be able to apply the 100 N force (or whatever your legs are able to supply). The longer the cranks, the more limited is the angle through which one is able to crank, and the more "dead rotation" one has to do. Long cranks also mean that one's knees will often try to apply pressure in less than ideal position.
At the other extreme, if you use 125-mm cranks (available on a few junior bikes), your legs and knees will always be in the ideal position, available to output maximum force. This is why proponents of short cranks tell you they pedal in a "better circle" with short cranks. However, the cranks will be so short that you won't be able to apply any real torque.
Combining both factors (longest crank for maximum torque vs shortest crank for ideal position throughout the circle) is at best an empirical science. There are a few formulas either based on frame size, leg length or upper leg length. The latter formulae seem more precise, but again experience is better than formulae.
