Anybody have a suggestion about what length of crank one should use. 170,172.5 or 175. I am 5-9 and have a inseam of 32" I like to spin at a high cadence 92-97. I have no idea if any of this information is relevant to the question at hand. Thanks for the help.
I would guess 172.5, but again that’s a guess, based mostly on what I have overheard people who looked knowledgable talking about. I think there are other things that play in, but I know height can be important and as I said, I would venture a guess you are in the 172.5 range. That is the standard crank most bikes will come with and I think you are a pretty average height. Let’s see how my educated guess holds up against the wealth of knowledge that is Slowtwitch.
before you get a crank, for the hell of it, put your exact leg inseam into the forumla you will find on this page (and read what it says too):
http://www.nettally.com/palmk/crankset.html
you will discover that this formula might tell you to use a crank length pretty different from what the dudes at the local bike shop suggest. right now there is very little good science as to the selection of proper cranks. but read the website above and use your common sense. that is the best way to pick your cranks.
You are lucky you have a standard inseam. I am 37 so I have to get custom 200 with what ever I get. Expensive.
Dave
Based off a 32" inch inseam you actually fall in that perfect range where 170 to 175 mm cranks are where you likely ought to be. This is good for you. The selection is endless and those lengths are a dime a dozen on eBay.
Chad
hmm…that’s a pretty interesting site. What’s funny is that after reading everything, I was expecting some crazy answer, like 200mm or 150mm–so what comes up?? 172.5, exactly what I’m using…
Is there a different formula if you’re using Power Cranks or Rotor Cranks??..
then that works for you.
i am only 5’10", but with my legs and the formula, i get a number over 180 mm.
There’s a very easy way to determine what crank length to ride. What’s on your bike right now? That’s what you should ride.
All of Mr. Cheese’s studies aside (no I haven’t even bothered to read them) I seriously doubt that most people could get on two bikes that are otherwise identical except for crank length and distinguish 170’s from 177.5’s, let alone 172.5’s vs 175’s. C’mon, we’re talking about 2.5 millimeters. Just ride what you have unless you’re shorter than 5’ or taller than 6’5".
Actually you can tell the difference between 177.5 and 170 or so, at least I can. However, after many miles of testing I have not determined which is better. Some conclusions I have are: if you like to spin higher cadences, go with shorter cranks. If you like to stand a lot, use longer cranks. Longer cranks require that your legs are in great condition, especially the up stroke (power cranks). But don’t assume that you will do better on shorter cranks if you are not in optimum condition. What feels the best might be the best choice. While I generally think shorter is better for me, I have had some of my best times on hill climbs with longer cranks. So who knows. The guy that said ‘whatever is on your bike now’ is probably right.
from pezcycling news:
CYFAC, the legendary French frame maker under the leadership of Francis Quillon—who built frames for such riders as Hinault, Fignon, Virenque, and Vandenbroucke, to name just a few—has always been at the forefront of bike design paired with cutting-edge materials. We get the low-down on how they achieve the perfect fit…
Small but Mighty
Although a small company in the French Loire Valley, with an absolute annual production capacity of about 2,000 frames, CYFAC nevertheless boasts a Ph.D. in Sports Biomechanics among its small staff. Dr. Matthieu Papin worked jointly with CYFAC and the French National Institute of Sport in Lyon to develop the CYFAC POSTURAL FIT CABINE, a fit study system which produces a frame design and rider fit protocols. The Postural Fit Cabine has taken CYFAC from their already pristine reputation as one of the top custom frame builders in the world, to an entirely new level.
Pez: Describe for us how the typical rider should select crank length. What are the factors they should consider and what are the general guidelines?
Matthieu Papin: Cyclists typically select crank length based solely on the measure of their inseam. To do so, some apply a constant coefficient such as I*0.2 (inseam measurement x 0.2) or trust a value table that was developed empirically. In all honesty, these methods do not allow for satisfactory results on either the medical-scientific or sporting fronts. With the development of the Cyfac Postural System we scientifically determined a multi-factor mathematic formula that permits the definition of the optimal crank length. This formula was defined after having done the following scientific observations:
During the pedal cycle, crank length dictates the joint amplitudes of the ankle, knee, and the hip. The longer the crank length, the greater the top-to-bottom cycle each joint must accomplish. Medical-scientific data does, however, define certain angular limits that are specific for each one of these joints. The closer to the limit (or beyond it) the more stress the system feels.
With the use of shorter cranks and a higher pedaling cadence we limit the forces applied to the muscular-tendon system. In overview, cranks that are too long put too much stress on the joints. The increase in pedaling cadence with shorter cranks also increases the kinetic energy of the pedal stroke. Consequently, the cyclist’s energy output is improved by an inertial effect. The scientific results show that muscular coordination of lower limb muscles is facilitated with the use of shorter cranks. As such, at the same power, pedaling is more fluid and cadence is increased. This is more efficient, less stressful, and leads to a better performance. Using the Cyfac Postural System, the 5 major parameters that determine crank length are: inseam, age, gender, level of riding, pre-existing pathologies.
The longer the crank length, the greater the top-to-bottom cycle each joint must accomplish.
great theory, unless, of course, the rider’s limbs are longer.
i do not feel that everyone should ride really long or really short cranks, or, worse, pick the right crank length with a roulette wheel. but if one goes with the assumption (and i do realize that this is a tenuous assumption) that 170s are right for someone, then logic follows that they are right for that someone because the length of the crank arms are proportional to something (or more likely, many somethings) in their lower body, like limb lenghts: femurs, tibias, feet.
so, if most of the other riders on earth have slightly (or vastly) shorter or longer limbs than that of mr. someone above, in my fuzzy logic, it stands to reason that these folks should be riding proportionally longer or shorter cranks. and sometimes a lot longer, or a lot shorter.
but sadly, irrelevant to mr. cheesehead-committee’s claims, their really ain’t no good science yet to prove or disprove this.
yeah, i would agree with you that telling apart 170s from 172.5s is very, very difficult. but telling apart 170s from 180s ain’t hard at all.
and i really like this line, “There’s a very easy way to determine what crank length to ride. What’s on your bike right now? That’s what you should ride.”
damn, i’m gonna open a bike shop! and make a lot of cash! my customers will be coming in to buy a bike, i’ll have them straddle one, they’ll ask me what the is right size frame to ride, and i’ll say: what frame are you on right now?–that’s the size you should ride!" i’ll only have to stock one frame size and no one will be the wiser…
you are funny.
My point is that most manufacturers already put shorter cranks on smaller frames, and longer cranks on the larger frame sizes. If you buy a 48cm bike you’ll likely get 170 or 172.5mm cranks stock. If you buy a 58cm frame you’re likely to get 175’s or 177.5’s. Unless you’re an anatomical anomaly with crazy proportions, there’s no reason to change them out from what’s on there from the factory.
If your 5’9" and your a male and your not into sprinting (serious sprinting anyway) I would go with 172.5 as mentioned above. 170 are very short, and 175 are what I use and Im 6’2". Ive tried 177.5 for 3 months and could never develop the power of 175 (I have long legs).
I swear I (6’3" 34in inseam) can tell the difference between 175mm and 172.5mm (easier to spin the smaller). It might be in my head, but I noticed this before I checked the crank lengths.
if one goes with the assumption (and i do realize that this is a tenuous assumption) that 170s are right for someone, then logic follows that they are right for that someone because the length of the crank arms are proportional to something (or more likely, many somethings) in their lower body, like limb lengths: femurs, tibias, feet.
so, if most of the other riders on earth have slightly (or vastly) shorter or longer limbs than that of mr. someone above, in my fuzzy logic, it stands to reason that these folks should be riding proportionally longer or shorter cranks. and sometimes a lot longer, or a lot shorter.
I don’t have any problem with your logic. I think the premise behind Mr. Kirby’s formula makes sense because in most cases our entire body is sized and fit to a bicycle—or rather the bicycle is sized to fit our body—except in the case of the crank. I’m not sure if his exact formula is perfect, but I tried it out with some 190mm cranks and they were great. Now all my bikes have 190s (PowerCranks actually) and I had my best spring of racing ever. I’m not saying it was only the cranks because I did a lot more training than the year before, but I felt very comfortable and powerful riding the 190s. I certainly won’t go back.
The fact that someone like Leonard Zinn uses the formula and has a lot of tall customers (he is 6’6” himself) that buy his long cranks and love them lends a lot of weight to the argument for proportional-length cranks.
Chad
So let’s get back to the original question. His inseam is 32inch, so if we use the fomula, 32inchx20.5=166mm. So he should be using 165ish right? Now, I have a 73cm inseam so it comes down to 150. Right now I’m using 172.5 because that’s how it came with the bike. but i know that there was something wrong and now i know it was a crank length. and i know 150 is going to work because I just measured my folding bike which has 145 crank, it’s a single gear bike but I can climb uphills easily. Can’t anyone make adjustable crank? so that finally people will realize that crank length should be proportion to something. (maybe muscle, leg length, length of tibia… )
Anyway, does anyone know where I can get those really short cranks?
Of course they´re gonna feel somewhat different, but I seriously doubt that anyone can prove that their faster or more efficient on either.
You´re body will get accustomed to whatever cranklenght you chose to go with unless it´s extreme of course.
It’s true that somewhat you’ll get accustomed to the whatever the length you are using, which makes the study more difficult. Yet, I bet if you can compare after you accustomed to whatever the length is, for instance, comparing after you practice riding with 160 and after you practice riding with 180 would make a big difference. but it’s just hard to conduct those kind of studies. I think it’ll be easier if we get people who don’t excercise and put them on the bike with different crank length.
Therefore, I’m still looking for 145-155 cranks. Thanks!
Anybody have a suggestion about what length of crank one should use. 170,172.5 or 175. I am 5-9 and have a inseam of 32" I like to spin at a high cadence 92-97. I have no idea if any of this information is relevant to the question at hand. Thanks for the help.
What I find funny is how many people will suggest a crank length that is significant down to 1/2 of a millimeter based off of a measurement that is only significant to within 25.4 millimeters!
I’m also getting a kick out of that Cyfac fit system that claims to be super-scientific and then bases the crank length on things such as gender, age, and ones favorite cereal. The sheer audacity of that is beautiful.