1) Drewjc: The info on the 190 mm cranks Indurain used on his hour record came from Velo News and Cycle Sport magazine, 2 of the most credible bicycle racing publications out there. Cadences of over 200 rpm are not uncommon, I just don't work at it too often, being more concerned at what I do for real on the road, and that is time trialling at 95-105 rpm and field sprinting at 120-130 rpm. That's about all you will ever need for road racing. I think the current record holder for the hour record on rollers rode over 200 rpm for an hour!!!
2) Ant Evans: Gearing is gearing and leverage is leverage. The two are unrelated. If you have ever jacked up a car to change a flat tire, you should be thankful the jack handle was fairly long instead of a few centimeters long. That is leverage. Longer levers (cranks, jack handles) move a static force or resistance with less force. The downside, if you want to call it that, is it takes a longer lever more time to complete the cycle.
Let's say we had two hypothetical cranks 1 cm & 100 cm long. At 40 kmh it would require a gear-cadence product in the neighborhood of a 53x15 at 90 rpm. That gear-cadence combination would produce 40kmh uphill, downhill, with a short rider, a tall rider, 1 cm cranks or 100 cm cranks!!! Turn a 53x15 at 90 rpm and you will always go 40kmh!!!
The crank length would only effect the diameter of the circle the legs would have to turn, and how much pedal force the legs would have to exert. Short cranks are like short jack handles. The stroke or cycle is completed faster but at the expense of leverage, requiring more force. Longer cranks move slower but have more leverage and require less force. Since most folks find big gears hard to turn, longer cranks will always make it easier to turn the same big gear than with shorter cranks.
If you read my earlier post, I already said longer cranks slow your legs down a little and force your legs to turn a bigger circle. As far as gearing goes it makes it easier to turn a higher gear, not a lower one. The difference between cranklengths is not enough to be one cog.
Moving up to longer cranks (or down) is a small, but noticeable difference. A good rider is good not because of ONE way he trains or ONE piece of equipment, but rather the sum of the parts; longer cranks are only a "spoke in the wheel."
Ant, your height is not really a factor. I might be taller than you, but if we both had to jack up a car to change a flat tire, we would BOTH find it easier to get the car off the ground with a longer jack handle. Even if you are a "short *******," I think you will find longer cranks make overall road riding better, especially climbing and TT'ing. The track is one case where short cranks are better, due the high leg speed needed. What the hell man, give them a shot. If you don't like them, someone will buy them from you, minimizing the finacial impact of this experiment. Life is short - go for it and see what happens!!!
Finally, whether you think longer cranks are good or bad, don't you think the coaches, team managers, and sponsers who backed Indurain and other greats in the TDF and the hour record cared about the outcome? Don't you think these guys had a lot on the line if their star rider failed??? To get a rider to that level, don't you think they know what they are doing???
The trend for these cycling greats is to ALWAYS go to longer cranks for important races, never shorter ones.