For those of you whom I've already bored with my crank length ramblings on other forums as 531Aussie, feel free to ignore the following.
Fergie, I gather you're looking for hard data rather than anecdotes, but here's mine anyway:
The short version: I'm 182cm with long-ish legs (89cm inseam) and size 43 feet. After a long-ish period of time using 170s a few years ago (prior to which I'd used 170 to 175, all for extended periods, and 165s for a couple of years on the track), I bought some 180s and persisted with them for roughly a year. I came to the conclusion that, when riding seated, the power 'issue' with longer vs shorter cranks is that, put very simply, it's a wash: while there's some extra leverage with longer cranks, they put the rider in a worse/weaker (lower) positon (weaker range of movement), so you can't use the extra leverage. In other words, the leverage is there, but the pedals are harder to push through most of the downstroke due to the extra knee and hip flexion, so any benefits are mostly nullified. Overall, I suspect I produce more slightly power on shorter cranks (172.5), when seated, at least (pedalling off the saddle is a very different story).
Longer version:
About 8 years ago, I became a bit obsessed with the idea of trying long cranks after an occasion where I accidentally put myself in a blind crank length test. I was doing a lot of commuting on a crappy bike with 170mm cranks, and the commute had a handful of steep-ish, short hills. One sunny day I dusted off one of my old racing bikes and took off. When I got to the regular hills, I flew over them!!! I was doing these climbs in a gear or two higher than normal, and couldn't work out why. I even got off the bike to check that it had the same cassette and chainrings that were on the other bike, and they were the same. It obviously turned out that this bike had longer cranks: 175mm. So, that was it, I
had to get longer cranks on all my bikes
The commute was very short -- ~20km -- and was just to uni, so I wore casual clothes and jogging shoes with clips and straps. I think by 'flopping' my feet somewhat 'arbitrarily' on the pedals with the jogging shoes was why I didn't immediately notice the different length.
A couple of months later, after getting some cash together, and reading all the long crank stuff on the net, I got a couple of pairs of 180s. I initially loved them, and I suspect the placebo effect helped me have a few months of great rides and good races, during which I felt like I was riding pretty strong. I was particularly addicted to the extra power I'm sure i got when riding off the saddle. In my opinion, when the rider isn't 'constrained' by 'regular' joint angles when riding seated, the leverage of riding off the saddle with long cranks is definite and noticeable. I loved the 180s on rolling hill courses and some crits where I spent a lot of time off the saddle stomping out of corners and bridging graps. Long cranks
are GREAT for riding off the saddle at low to moderate revs. I remember Pantani sometimes used 180s for mountain stages, and, as far as I recall, he spent a lot of time doing clibs off his seat.
After about 6 or 7 months with the 180s, my position suddenly started to bug me big time. I started to feel very low, relative to the pedal at the top of the stroke, and became more and more frustrated at not being able to "get on top of" the pedal through most of the downstroke. Despite this, i persevered for a few more months. The long cranks kept bugging me more and more, and when I started getting persisted medial pain in both knees, I began swapping between my "180 bikes" and one of my 'short crank' (175mm) bikes. The 175s didn't hurt my knees, I preferred the postion they put me in, and I felt that I rode just as well with them, if not slightly better. I loved that I was so high over the pedals that I could really pound the crap out of them. It was a big decision,
but after spending probably another month or two switching between 180s and 175s I eventually sold the 180s and went looking for shorter cranks.
My local shop had a great deal on 2 pairs of DA 172.5s, so I bought them. I probably woulda been just as happy with 170s, or even 175s, but I took at shot at the 172.5s, and ended up liking them a lot.
The 172.5s are my main length, but I did occasionally miss the 180s on rolling routes, so I bought some 177.5s that I use every now and then.
I'm not a sprinter, so cadence was never an issue for me.
As others have suggested, aerodynamics is most likely always gunna me more important than any possible power differences obtained by using longer cranks, so if long cranks put your knees in your chest and it stuffs up your aero position, it's pointless.
To sum it up: as a former Olympian says about the subject: "If ya're farkin flyin', it doesn't matter what ya farkin use."
Eh, I've lost interest.
......
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