I’m 6’3 with an inseam of 34…I have 175 cranks. What determines the length of cranks one should use? Should I be using longer cranks, like 195-200. What could potentially be the effects (pos./neg) to switching to longer cranks?
IMO, your height and legs definitely call for the use of 180s for tt and tri races (longer cranks would probably be better, but other than custom, good luck finding longer).
Read this:
http://www.nettally.com/palmk/crankset.html
When using the formula in the above mentioned link, I’m supposed to ride a 202mm crank length. I currently ,and for years, have been using a 180mm. FYI - I’m 6-2 with a 37" inseam. I am a triathlete and TT’er. I do not do raod races. if I did I would back off to the 175 so that I could more easily adapt to peloton speed changes. The 180’s take awhile to get up to speed.
I think they are plenty long enough. In fact if they were any longer I’d have a hard time pushing them.
I’ve got a 34 inch inseam and use 172.5mm cranks. The crank length does not always directly relate to your leg length. The increased torque you can apply to the pedal has only an indirect relationship to an increase of power at the rear wheel. Also over long periods of time, longer cranks can cost you energy as it is very difficult to be efficient with them.
-SD
The crank length does not always directly relate to your leg length. The increased torque you can apply to the pedal has only an indirect relationship to an increase of power at the rear wheel. Also over long periods of time, longer cranks can cost you energy as it is very difficult to be efficient with them
If you don’t mind me asking, how do you know these three things (above)? Have there been any physiological studies that say or support any of these three statements? If there are, they must be somewhat new, because, as far as I know, no such studies exist. I can say I have a 39" inseam and use 165 mm cranks, but I am not sure what that would show or prove.
As far as I know, the sad reality is that much of what is done in cycling (such as the selection of crank length for a particular leg length or for a particular course or event) is based purely on tradition, habit, and, perhaps most important, the sheer lack of availability of bicycle components (such as cranks) that really range in size.
Rocketman, I posted that link because it makes some interesting conclusions based on some commonly held assumptions. And it got me thinking.
It may not be gospel, but I think it shows clearly that much of what we are told about “proper” crank length is sheer bunk. If you read most of the stuff on the link(s), it is easy to see how manufacturing needs and bicycle design constraints have played far more powerful roles in our choice of crank lengths than physiological optimums.
I don’t mind you asking. I’ve tried different crank lengths. Tested with them. Tested my times over known terrain as well as a computrainer. I use a bicycles in many disciplines, not just effort against the clock. I know that my 200M flying TT is 1/4 of a second slower with 170 mm crank arms over my time with 165mm. I’ve done dozens and dozens of trials. I’m faster with 165mm cranks in a flying 200.
In max power output tests, I’ve been able to attain 1560 watts as a peak number, but only been able to hold that effort above 1000 watts for 3-4 seconds. That trial was done with 180mm cranks on a .5% grade. With 172.5mm cranks my peak power output dropped to 1475 but I was able to average 1000 watts for 11 seconds. A more useful range for my application. I have several more personal trials I’ve conducted with repeatable consistant results.
I wasn’t suggesting that shorter is better, However, because the “window” for puting effort into forward thrust is small compared to the amount of time that leg is not applying peak power, the time in between for me should be minimized.
To oversimplify; in running, if you can increase your stride 1" and maintain the same gait, you’ll be faster, so why not run with a 5’ stride?
Length, turnover, and most importantly efficency are paramount and should seek to be maximized.
Try short and long, try them all, please don’t try pedalling those 220mm Zinn cranks through turn 4 at Downers Grove.
-SD
check Pezcycling news or Volonews I believe they have a discussion about drank length and inseam. If I recall 31 inch inseam translates to 175mm. It was around 5-10 months ago. I’ll see if I can find it. Try a google for biycyle crank lengths.
Good luck gtting an answer on this one.
Crank length questions open a bigger can of worms than PC questions, because - are you ready - there is no consensus opininion supported by scientific research. If you read enough on this subject, you will come up with anecdotal evidence to support whatever you want to believe.
BTW, if one were to try to answer a question like this, inseam would not be nearly enough information from which to draw a meaningful conclusion. A real analysis of crankarm length would (at least) involve an understanding of how the crankarm functions as part of a linkage system (femur/lower leg/foot/crank.) I think Dave is on the right track; one can perhaps infer from his empirical results that different torque/cadence/speed relationships may suggest different optimal crank lengths…
try looking at this site:
http://cranklength.info/
.
Great link. Few things are as simple as they seem…
Show me 'da money.
What studies, authors, journals, dates, etc. please?
Mr. Oracle, I thought you were the “where’s the science?!” type.
So you say, ‘yes’ to my last question and then are awfully quiet.
So where IS the science?
oh, Oracle, where are you, Oracle? I await your science…
any chance of a reference to the study you mentioned?
Can you point me to a study that supports your “yes” answer?
I am not the one you seek, but here is one reference on the no side
** **Can J Appl Physiol. 1997 Oct;22(5):429-38.
The conclusion;
The results of the study suggest that each subject has a most efficient crank arm length, but it does not appear that optimal crank arm length can be predicted by leg length.
There does seem to be some data for both sides although the link you posted originally starts without ever defining the “optimal length”, optimized in regard to what parameter?
The crank length does not always directly relate to your leg length. The increased torque you can apply to the pedal has only an indirect relationship to an increase of power at the rear wheel. Also over long periods of time, longer cranks can cost you energy as it is very difficult to be efficient with them
If you don’t mind me asking, how do you know these three things (above)? Have there been any physiological studies that say or support any of these three statements?
Yes.
Get over yourself …
Strange… I didn’t edit that post.