Crank arm length?



531Aussie said:
I'm not shooting the messenger, but......

I don't like that formula, in fact, I don't think anyone does :)
There's no pro in the world over about 5'5" is using cranks relatively that long. I don't know how Zinn still gets away with it. I'm only 6ft, and the "conservative" formula puts me on 188mm cranks. It's crazy! :)
The hour record holder
 
POGATA said:
But Sosenka is 6'7"!!! :eek: It says on Bike Cult that he used 190s.

What would his inseam be? I'm 6ft, and my inseam is 89.5, so his would be what, 100cm? That means Zinn and Palm would have him using ~215mm cranks :rolleyes: . If only he knew
 
El Loto said:
I should go for 195mm cranks apparently. I'm riding 175s at the moment.
I hope you're joking :)

How tall are you? If you're pretty tall, perhaps get some 180s and see what you think.

Long inseam or not, having cranks that long means getting a new bike, because of ground clearance and front wheel clearance (from your toes), and you could have even have issues with your feet smashing into your rear derailleur and chainstays
 
531Aussie said:
But Sosenka is 6'7"!!! :eek: It says on Bike Cult that he used 190s.

What would his inseam be? I'm 6ft, and my inseam is 89.5, so his would be what, 100cm? That means Zinn and Palm would have him using ~215mm cranks :rolleyes: . If only he knew

Hmmm. I think crank length calculations are about as valuable as that whole KOPS deal, which is to say not very much. At best such calculations are only starting points. I do think, though, that Zinn's is one of the wackyest ones. Sometimes Lenny is way out there.
 
alienator said:
Hmmm. I think crank length calculations are about as valuable as that whole KOPS deal, which is to say not very much. At best such calculations are only starting points. I do think, though, that Zinn's is one of the wackyest ones. Sometimes Lenny is way out there.
I agree. There's no doubt that the 'issue' is WAY overrated. Despite big claims by some, and amazing 'testimonies' by others, pros as still smashing fantastic times on normal length cranks.

I've thought of possible formulas involving a sliding scale -- percentage of inseam reducing as the legs get longer -- but who knows? All I've concluded is that tall people, most likely, should be using longer cranks that short people, but "how much longer" is obviously the question.

The 3 main advocates of long cranks have the same story: there are all tall guys who were frustrated in the old days by 175mm being the longest cranks they could get. So they finally got some long cranks, which felt great to them, then they make up some formula to suit their preferences and generalisations. :) Kirby Palm got his 'formula' from, "a heap of short riders with 31-inch inseams used 170mm cranks", ergo, the magic 21.6% was born. I couldn't believe that's where he got it from. All those pages, and his formula is based just on that 'fact' and his personal preference. He knows everyone used 170s at one time, so why didn't he believe that the guys with 32" inseams were suited to 170s, or the guys with 33" inseams? Etc, etc.

Another probelm with long cranks is that they are addictive; when someone first uses them they (often) immediately notice the extra leverage (especially off the saddle on short climbs), so become hooked,and find all sorts or reasons and new positions to keep using them.

When I first got on 180s (I'm only 6ft), I was like, "wow, the leverage", so I was hooked for about a year. I was so convinced that I had an advantage that I moved my saddle to all points of the bike to make them work, ignoring the fact that my knees were in my chest, I couldn't 'get on top of the pedals', and my hamstrings and medials were killing me. The day I put 175s back on my bike I felt like Superman :) because I could get over the pedals and pound the **** out them


anyway, I forgot what i was talking about......oh yeah, stay out of my booze!!
 
531Aussie said:
anyway, I forgot what i was talking about......oh yeah, stay out of my booze!!

Yeah, yeah, yeah. It's not like you can actually appreciate it. You NZed'ers (Australia is just West New Zealand) can't hold yer booze. I know. I had friend visit Tucson from NZed, so I took 'em out on the town. What did he do to show his appreciation? He spent the whole day pukin' and gaggin' at local tourista places and all over the highway betwixt here and Phoenix.
 
PARLEEEEEEEEEEEEEZ!!! New Zealanders can't drink!!! :)



alienator said:
(Australia is just West New Zealand)
Crikey!! Duck for cover :) At least you know what NZ is -- you must be the only Yanks who's ever even heard of it.
 
531Aussie said:
At least you know what NZ is -- you must be the only Yanks who's ever even heard of it.

That's why I'm an outcast in my country: I can point out other countries on a map; I learned another language and studied in another country; and I can pronounce "nuclear" correctly. FWIW, it's not nukular like our Fuhrer says. IMHO, if you can't pronounce nuclear, you shouldn't be allowed to have the keys to the nuclear weapons.

Maybe if you folks had the decency to produce a lot of oil, Americans might actually take interest and learn more about your part of the world. I mean, without oil, what do have to offer?
 
alienator said:
That's why I'm an outcast in my country....
you poor soul :p ...........and, close, but it's "nookila"



alienator said:
Maybe if you folks had the decency to produce a lot of oil, Americans might actually take interest and learn more about your part of the world. I mean, without oil, what do have to offer?
Our half a continent load of uranium is not enough? :)
 
531Aussie said:
Our half a continent load of uranium is not enough? :)

Well, I have to be honest. We're broadening our War of Terror, and apparently week after next, we're going start liberating Australia....and your Uranium. We'd start sooner, but we need some time to make up a connection between Osama bin Laden and you folks.
 
alienator said:
Well, I have to be honest. We're broadening our War of Terror, and apparently week after next, we're going start liberating Australia....and your Uranium.
Cooool!! I look forward to having my very own pair of Freedom Jackboots
 
531Aussie said:
But Sosenka is 6'7"!!! :eek: It says on Bike Cult that he used 190s.

What would his inseam be? I'm 6ft, and my inseam is 89.5, so his would be what, 100cm? That means Zinn and Palm would have him using ~215mm cranks :rolleyes: . If only he knew
I`m 180 cm, my inseam is 93 cm, i`ve used 172.5, 175 and 180, and there`s no doubt that the 180s works best for me. I`ll be getting adjustable cranks(180-220) in a few days and will be testing them in the coming weeks and months.

Did you read the article on Sosenkas site? It says:

I have some calculations on my desk, proving that 190 is not the ultimate length for me. And that with longer cranks my performance would be as from another planet
 
531Aussie said:
I hope you're joking :)

How tall are you? If you're pretty tall, perhaps get some 180s and see what you think.

Long inseam or not, having cranks that long means getting a new bike, because of ground clearance and front wheel clearance (from your toes), and you could have even have issues with your feet smashing into your rear derailleur and chainstays
whats wrong with a bike that fits?
 
531Aussie said:
I agree. There's no doubt that the 'issue' is WAY overrated. Despite big claims by some, and amazing 'testimonies' by others, pros as still smashing fantastic times on normal length cranks.

I've thought of possible formulas involving a sliding scale -- percentage of inseam reducing as the legs get longer -- but who knows? All I've concluded is that tall people, most likely, should be using longer cranks that short people, but "how much longer" is obviously the question.

The 3 main advocates of long cranks have the same story: there are all tall guys who were frustrated in the old days by 175mm being the longest cranks they could get. So they finally got some long cranks, which felt great to them, then they make up some formula to suit their preferences and generalisations. :) Kirby Palm got his 'formula' from, "a heap of short riders with 31-inch inseams used 170mm cranks", ergo, the magic 21.6% was born. I couldn't believe that's where he got it from. All those pages, and his formula is based just on that 'fact' and his personal preference. He knows everyone used 170s at one time, so why didn't he believe that the guys with 32" inseams were suited to 170s, or the guys with 33" inseams? Etc, etc.

Another probelm with long cranks is that they are addictive; when someone first uses them they (often) immediately notice the extra leverage (especially off the saddle on short climbs), so become hooked,and find all sorts or reasons and new positions to keep using them.

When I first got on 180s (I'm only 6ft), I was like, "wow, the leverage", so I was hooked for about a year. I was so convinced that I had an advantage that I moved my saddle to all points of the bike to make them work, ignoring the fact that my knees were in my chest, I couldn't 'get on top of the pedals', and my hamstrings and medials were killing me. The day I put 175s back on my bike I felt like Superman :) because I could get over the pedals and pound the **** out them


anyway, I forgot what i was talking about......oh yeah, stay out of my booze!!
Sosenka is the world record holder!

Do you use a powermeter when testing the different crank lenghts?
 
POGATA said:
what's wrong with a bike that fits?
I was just letting the guy know that he might need a new frame if he gets 200mm cranks. If he's very tall, chances are he has big feet, so he'd probably have big issues with his heels smashing into the stays and the rear derailleur. I knew a guy with 'normal' cranks and big feet who had problems hitting his rear derailleur with his heels.


POGATA said:
I`m 180 cm, my inseam is 93 cm, i`ve used 172.5, 175 and 180, and there`s no doubt that the 180s works best for me. I`ll be getting adjustable cranks(180-220) in a few days and will be testing them in the coming weeks and months.]
180mm is (obviously) only 19.35% of your inseam. I'm not sure what you're saying. Are you saying you'll be better off with even longer cranks, or don't you know yet? Do you think I'm wrong dismissing Zinn's "21.6% of inseam" formula?



POGATA said:
Sosenka is the World record holder."
I'm aware of that. Once again, what are you saying? I'm saying that 21% or 21.6% of inseam is way too long, especially for taller riders. As I said, I doubt very much that Sosenka is anywhere near that. While I think that 21% is too long, I do believe that taller riders should use longer cranks, but not that long.

POGATA said:
Are Did you read the article on Sosenkas site? It says:

"I have some calculations on my desk, proving that 190 is not the ultimate length for me. And that with longer cranks my performance would be as from another planet"

I guess it begs the question: why didn't he use longer cranks for his record? I'm sure he did a bucket load of testing back then. Anyway, it doesn't mean anything to us unless we know his inseam.



POGATA said:
did you usea power meter with the different cranks"
No, I don't have a power meter. I persisted with 180s for about a year (i'm 182cm -- 89.5cm inseam, size 44 feet); I even bought 3 pairs!
I ended up with a bit of a screwed up postition, with my knees almost hitting my chest (especially when in the drops), and I was unable to 'get over' the pedals to really pound them. I know I started going better when I went back to 175s, and I sometimes even use 172.5s. The only time I missed my 180s was when 'surging' up short hills off the saddle, so I bought some 177.5s a few months ago, but I have ridden them much; I don't need them on the flats.

21.6% of inseam puts me on 193mm cranks, and 21% would have me on 188!! I can't even fathom that

I came to the conclusion that while longer cranks may provide more leverage, they're harder to push because the rider is in a relatively lower and weaker position, so it kinda cancels out. And that's without even getting to the cadence side of things.

I'll be happy to admit that I'm way wrong if pros start using super long cranks in the coming years and smash all the existing time-trial times, but until then, I'll maintain my "dubiousity".

This is a good article which outlines a couple of the conundrums of longer cranks: http://www.arniebakercycling.com/pubs/Free/Optimum Crankarm Length.pdf
Check the bit on "force and optimal crankarm length"

As some 'covnential' advocates has said, despite all the testing that's gone on, particularly by Zinn, no hard conclusions can be drawn that longer cranks make us faster.
 
531Aussie said:
As some 'covnential' advocates has said, despite all the testing that's gone on, particularly by Zinn, no hard conclusions can be drawn that longer cranks make us faster.
The most sensible response to this question in years. Remember that the current fashion for long cranks was set by Cyril Guilmard, the DS for Renault/Elf/Gitane during the Hinault and LeMond period. Hinault was periodically sidelined with knee problems.
 
oldbobcat said:
The most sensible response to this question in years. Remember that the current fashion for long cranks was set by Cyril Guilmard, the DS for Renault/Elf/Gitane during the Hinault and LeMond period. Hinault was periodically sidelined with knee problems.
ah shucks :p -- but I basically ripped it off Zimmerman: http://www2.bsn.de/Cycling/cranks.html (the article is pretty old, so some of the links no longer work)

He says something about lots of testing coming up with not much,
 
I recently pulled the cranks off my bike to clean them, and to my surprise, when I measured them, they were not the length I ordered on the bike when I purchased it in 2004! :mad: Having been professionally fitted by the top fitter in town at the time, as well as double checking with several online fit calculators that came to the same conclusion, I specifically ordered 172.5 mm, but these cranks are 175 mm!

Furthering regarding crank arm lengths, however, I am having trouble getting my head around some of the performance factors associated with longer or shorter cranks. Having had some right knee problems and surgeries, I wanted to lean towards shorter cranks with the theory that they are a little easier to spin at a higher cadence and may not put as much pressure on the knee as longer cranks. I also theorized that it would be a little easier to spin up the mountains with a shorter crank than a longer crank in my 39-27 gear.

But when I do a search on this subject, I keep coming up with information that seems contradictory to the above conclusions. For example, in this discussion on crank length at Sheldon Brown, he says "More well-rounded cyclists, who are likely to deal with wider variations in chainwheel and tire size, need a more sophisticated system to realize that the 46/16 on their mountain bike, and the 52/12 on their Moulton and the 52/14 on their Bike Friday are all about the same as the 53/19 and 39/14 on their road racer. But the fact is that a mountain bike with a 46/16 has the same gear as a road bike with a 53/19 only if they have the same length cranks. If the mountain bike has 175's and the road bike 170's, the gear on the mountain bike is really about 3% lower! If you go to longer cranks without changing any of the other variables, you will have more "leverage", which is another way of saying you'll have a lower effective gear."

To me, I associate lower gear with being easier to spin and higher cadence, and I was looking for the effect of having a lower gear with shorter cranks, not that effect from having longer cranks. What am I missing here? And most importantly, am I not correct in assuming that it will be easier to spin up the mountain in my 39-27 gear with a slightly higher cadence with slightly shorter cranks than it will be for me to spin up the mountain in my 39-27 gear with a higher cadence with longer cranks? On another note, I happen to have 170mm cranks on an old mountain bike, and I seem to be relatively fast and comfortable on that bike in situations spinning up a paved mountain road, not nearly so much slower compared to my road bike times over that same course that I would expect, further making me think I would be better off going to the slightly shorter 172.5 cranks on my road bike that all the fit calculations recommended for me.

I think it is probably way too late to get the bike shop to perform and give the size crank arms that I ordered though! :(
 
chainstay said:
To me, I associate lower gear with being easier to spin and higher cadence, and I was looking for the effect of having a lower gear with shorter cranks, not that effect from having longer cranks. What am I missing here?
The issue is pedal force is inversely proportional to pedal speed, at the same power, and pedal speed is proportional to cadence times crank arm length, so a longer length, at the same cadence, allows for less pedal force, or equivalently at the same force a longer crank allows for a lower cadence. The argument is that muscular engagement (fast twitch versus slow twitch) is dependent on force and speed of the muscle contraction, rather than on the cadence. The same muscle speed and force occurs at lower cadence with longer cranks, at a given power.

Pedal force isn't the whole issue, of course, but then neither is cadence.

Dan