an explanation with some reasoning to support the idea of proportional bicycle crank length:
http://bicyclecranklength.blogspot.com/
read, and fire away …
THAT’S your long awaited proof? Ummm…OK…
edit: It’s a good thing you didn’t post this yesterday 
I’m sold…
I’ve always just used the standard (172.5) cranks that came with whatever bike I purchased. Recently I bought a used Titnaflex from Paul (Zipp here on ST) that came with aftermarket 195’s on them. Originally I was just going to pass them on to another ST’er who showed interest in them since Paul was going to include the original standard cranks that the bike came with as well.
Well, when the sale went through Paul was unable to find the original cranks, and thus just discounted them from the purchase price and all I had was the 195’s. Thank God it turned out that way— As a result I’ve kept the 195’s and they have been Absolutely Fantastic for me.
All I can say is that I’m sure it’s very individual as to whether a shorter or longer crank length will make a difference- but believe me, in some cases it really can- and you don’t know until you try.
steve, how tall are you?
Steve, could you also be a bit more descriptive about how they are “Absolutely Fantastic” for you? Thanks.
THAT’S your long awaited proof? Ummm…OK…
edit: It’s a good thing you didn’t post this yesterday
Especially since he neglects to discuss what has already been published, e.g.:
While the extremes of crank length clearly matter, it is hard to generate much power on cranks of 10 mm length or cranks that are longer than your leg, the most likely outcome of your study is the athlete will test best on the crank length closest to the one they train with. If the athlete trained all the time on one of those “weird” cranks lengths, as long as it was not outside of the range of physiological potential one might find the athlete tested best at that length.
While crank length may make a difference, I believe it is almost certainly quite small for the normal lengths. But, the problem is it is almost impossible to test because you need to train the athlete on the length to know the potential of the length for that person. So, what I think is only a guess, as is everyone else’s opinion.
What is important here though is most athletes THINK it is important, therefore it is to them.
I’m only 5’8", 30" inseam. I’m stocky/muscular, and I think they work so well for me because they give my pedal stroke a fuller range of motion from top to bottom. Although you pedal in circles- the power stroke is basically a strong leg push down, and having my leg start higher up (like compressing a spring more) and giving me a longer power stroke has really worked well for me. I’m a bit closer to a masher than a spinner (my natural cadence is 85-90), and the bike included Q-rings as well- so the combination of the longer crank and the Q-rings has been awesome for my type build and pedaling style.
what would happen if we could take the same test subject and test him with the same basic protocol as before, but this time on every single crank length in the entire range between 50mm long cranks and 300mm long cranks: say, cranks every 5mm in length (e.g., crank lengths of 55mm, 60mm, 65mm, … all the way to … 285mm, 290mm, 295mm).
so if we took that as the next step of our study, what kind of data would we collect? and if we collected all those data points and then drew a line through them, what would the curve look like? again, since this experiment is imaginary, i cannot supply absolute numbers. but based on knowledge of the human body and the understanding that the human organism is an analog, not a digital machine, i think we can all agree that the curve though the data points collected in this part of the experiment would definitely NOT look like this:
fig. 2
I think you need to rethink that conclusion, this time taking into consideration the length-tension relationship at the sarcomeric level (which in fact is “digital”, at least by your use of the term).
again, i’ve read the study and e-mailed back and forth with Dr. Martin.
there are some quite signifiicant shortcomings to that study, ones that Dr. Martin acknowledges.
again, i’ve read the study and e-mailed to Dr. Martin.
there are some shortcomings to the study, even ones that Dr. Martin acknowledges.
There are shortcomings to every study. It is, however, the best evidence to date, and the results indicate that variations in crank length even beyond the normal range used by most cyclists do not measurably impact efficiency (in an independent sense, anyway). That result is actually quite logical when you consider that 1) it takes a rather large change in crank length to significantly alter joint angles/muscle lengths, and 2) at sarcomeric level, the length-tension relationship shows a broad plateau.
So you’re on a radically different bike, with different cranks, and different chainrings, but you’re sure the 195s have been fantastic?
Come on, we all know that longer cranks are terrible for ya. :o(
Dave
i would stand by that conclusion. this is why:
i do understand that the length-tension relationship at the sarcomeric level is “somewhat” digital.
but you still won’t get a curve that digital (fig. 2) when you put a guy on a bike with those cranks. as you know very well, it is not just one muscle at one length pushing those pedals around. it is a very complex system of many muscles, many joints, and many attachment points.
nor do i claim that the actual curve will be eggshell-smooth. but it will not be a line, it will be curved. and there will a peak somewhere on the curve.
nor do i claim to have all the answers, only that the research done so far shows a remarkably incomplete picture. and that highly incomplete picture means that, in my book, there is nothing wrong of thinking and asking: “what if ?”
that is how we learn more.
I’m only 5’8", 30" inseam. I’m stocky/muscular, and I think they work so well for me because they give my pedal stroke a fuller range of motion from top to bottom. Although you pedal in circles- the power stroke is basically a strong leg push down, and having my leg start higher up (like compressing a spring more) and giving me a longer power stroke has really worked well for me. I’m a bit closer to a masher than a spinner (my natural cadence is 85-90), and the bike included Q-rings as well- so the combination of the longer crank and the Q-rings has been awesome for my type build and pedaling style.
Thanks for the extra info. It’s very interesting in that the “long crank” proponents typically claim that they are a boon to taller riders which, no offense intended, I wouldn’t classify your height to be in that group.
It appears to me that you might possibly have been merely “overgeared” prior to acquiring the longer cranks. If you didn’t change your gearing and still pedal at the same cadence as before, the longer cranks merely lowered your “effective” gear ratios and increased your foot speed. The same thing can be easily accomplished simply by selecting lower gearing and keeping the cranks the same.
Steve, could you also be a bit more descriptive about how they are “Absolutely Fantastic” for you? Thanks.
Sure, I just feel that I am better able to transmit more power (force) on the downstroke with the longer cranks than with my previous ones. It just has a more “natural” feel for me to have my legs go up and down that extra 4cm. Normally it would be a 2cm higher and 2cm lower foot position due to the 2 cm longer cranks- but I have adjusted my saddle hight so that it becomes a 4cm higher and 0cm lower foot position - being that there is that optimal full extension angle that needs to be maintained.
Of course it is totally un-scientific- there are Sooo many other factors that come to play-- new bike that has me in a much better fit position than my old one (got to love Titanflex for position variability), the Q-rings (which are also awesome, in my view), and that it is a fairly new bike for me (got in just after the New year).
But I’m sure you’ve had the experience when trying on a new running shoe (or whatever other piece of equipment), and you just knew that it “worked” for you, even if you couldn’t explain exactly why-- well the cranks do that for me.
nor do i claim that the actual curve will be eggshell-smooth. but it will not be a line, it will be curved. and there willl a peak somewhere on the curve.
OK…if we make the unsupported assumption that the line is somewhat curved, what determines the location of the “peak”? Is it something inherent in the “structure” of the leg and crank system, or is it possibly merely determined by accomodation (i.e. the “peak” is at the crank length the riders are used to)? Sounds sort of like a “Which came first, the chicken or the egg?” type of conundrum.
i would stand by that conclusion. this is why:
i do understand that the length-tension relationship at the sarcomeric level is “somewhat” digital.
but you still won’t get a curve that digital (fig. 2) when you put a guy on a bike with those cranks. as you know very well, it is not just one muscle at one length pushing those pedals around. it is a very complex system of many muscles, many joints, and many attachment points.
nor do i claim that the actual curve will be eggshell-smooth. but it will not be a line, it will be curved. and there willl a peak somewhere on the curve.
nor do i claim to have all the answers. only that the research done so far shows a remarkably incomplete picture. and that there is nothing wrong, in my book, of thinking and asking: “what if ?”
I agree with your analysis. My criticisms are two.
-
I think the curve will be substantially flatter near the “optimum point” than you have drawn it (your curves may be for illustrative purposes only) and the drop off will be more severe as one approaches the limits. I suspect the curve will look more like figure two than you think it will.
-
The study must include time for the riders to train with the new length to fully understand the effects of the new length on power.
But I’m sure you’ve had the experience when trying on a new running shoe (or whatever other piece of equipment), and you just knew that it “worked” for you, even if you couldn’t explain exactly why-- well the cranks do that for me.
I’m cool with that…if it “works” for you and makes your riding experience more enjoyable for you, great…have at it 
I only have a problem with folks trying to take experiences like yours and presenting it as “proof” that longer cranks have some sort of magical properties
.