Crank lengths - make a difference?

myra-simon.com/bike/cranks.ht­ml

And there in one easy to find resource (and from the pages linked to) is all the snake oil and quackery you could ever hope for.

How is it, if it's all so scientific, that no-one can agree on the "magic number" you multiply your inside leg measurement by?

Or is it the measurement from the top of the femur?

Or is it the measurement to the top of the head when seated, subtracted from your height?

One of the charlatans (who is apparently a mechanical engineer) begins to justify his particular flavour of hokum thus: "... the formula is the mathematical result of three assumptions and one bit of empirical data."

LOL wut?

Three assumptions? That's a relief: I thought you were some bullshit merchant who went around making spurious claims based on only one assumption!

And this "emipirical data" turns out to be "...much qualitative observation and some informal testing...". That's it. This, from a mechanical engineer?

I said: "LOL wut?"

The references page really is a gem, featuring classics such as "...I haven't read them all myself...", "Reportedly, this mathematical model assumed a rigid ankle joint. If so, it's totally invalid." and the always popular "In other words, totally invalid."

I SAID "LOL wut?"

Another mountebank is reassured to find the numbers he's been touting, coincided with the findings of "...a couple of Californian researchers using a lab-full of machinery (Gross & Bennett, 1976)."

Nineteen seventy when? Skinny wheels, KOPS, aerodynamics? Dude, things have moved on! Stop getting stoned, walking barefoot in the sand and haul arse to the twenty-first century plz.

TL/DR
Although none of us agree and can't back anything up, we're still right.