Crank length

Where speeds may exceed 60 kmph

Re: Crank length

Postby Zujan » Sat Apr 03, 2010 11:25 am

Im running 175mm cranks and never had any problems at DGV.
But bear in mind that Im 195cm tall ,riding 60cm track frame and hate any race that goes shorter than 12 laps minimum.On my S2 Im running 177.5 cranks.
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by BNA » Sat Apr 03, 2010 2:38 pm

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Re: Crank length

Postby Alex Simmons/RST » Sat Apr 03, 2010 2:38 pm

I would suggest that the issues you are noticing with bike handling and feel are much more likely to be related to the frame and fork dimensions and angles, and overall bike set up, than they are with a 2.5mm difference in crank length.
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Re: Crank length

Postby monzy » Thu Jul 08, 2010 2:28 pm

I have got an old pair of 180mm Campy Pista cranks laying about..... You must need to be a giant to ride using these!. I have never seen another pair that long...
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Re: Crank length

Postby brentono » Thu Jul 08, 2010 3:46 pm

monzy wrote:I have got an old pair of 180mm Campy Pista cranks laying about..... You must need to be a giant to ride using these!. I have never seen another pair that long...


Got to be very rare (possibly for motorpaced useage, if they is quite old) good-one :wink:
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Re: Crank length

Postby mikesbytes » Thu Jul 08, 2010 10:39 pm

brentono wrote:
monzy wrote:I have got an old pair of 180mm Campy Pista cranks laying about..... You must need to be a giant to ride using these!. I have never seen another pair that long...


Got to be very rare (possibly for motorpaced useage, if they is quite old) good-one :wink:
Cheers,
BrentonO


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Re: Crank length

Postby brentono » Fri Jul 09, 2010 4:50 pm

On TT? :wink:
At the Serotta International Cycling Institute Science Symposium, Jim Martin, Ph.D.,
from the University of Utah presented his study of crank length.
Attention: Time Trialists
Martin's study has a specific application for time trialists. Traditionally, TT specialists switch to 2.5- or 5-mm longer cranks for races against the clock, believing that greater length provides more leverage to push big gears during a time trial’s steady application of force.

However, Martin argues that because crank length doesn’t affect power production, time trialists should use the shortest commercially available crankarms -- 165 mm. This will let them have a lower and, therefore, more aerodynamic position that's likely to result in a faster ride.

After all, long cranks are longer not only on the downstroke but also at the top of the stroke where, in a time trial position on aerobars, the rider’s thighs tend to hit the chest. The longer the crank, the more the chest must be elevated, thus increasing frontal area and wind drag.

So with short cranks, a rider can get the chest lower without leg interference. The importance of a low frontal area in time trials is unquestioned. Pro teams spend thousands of dollars for wind tunnel research so they can determine the lowest and fastest position for their riders without compromising power. But they do it on bikes with long crankarms -- often even longer than normal.

Thanks to Martin’s new study, we now have new knowledge: Short crankarms allow a lower aero position
without compromising wattage output.

I mention M.P. because (back in the day, B.C.) they rode such huge gears, the thought was that the very long cranks,
gave them a rolling advantage, at least that was the thought, as I observed and was told from the competitors,
at the World M.P. Champs... behind the Harleys for the last time (as far as I know)
Hope that helps,
Cheers,
BrentonO
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Re: Crank length

Postby Nobody » Fri Jul 09, 2010 6:45 pm

brentono wrote:On TT? :wink:
At the Serotta International Cycling Institute Science Symposium, Jim Martin, Ph.D.,
from the University of Utah presented his study of crank length.
Attention: Time Trialists
Martin's study has a specific application for time trialists. Traditionally, TT specialists switch to 2.5- or 5-mm longer cranks for races against the clock, believing that greater length provides more leverage to push big gears during a time trial’s steady application of force.

However, Martin argues that because crank length doesn’t affect power production, time trialists should use the shortest commercially available crankarms -- 165 mm. This will let them have a lower and, therefore, more aerodynamic position that's likely to result in a faster ride.

After all, long cranks are longer not only on the downstroke but also at the top of the stroke where, in a time trial position on aerobars, the rider’s thighs tend to hit the chest. The longer the crank, the more the chest must be elevated, thus increasing frontal area and wind drag.

So with short cranks, a rider can get the chest lower without leg interference. The importance of a low frontal area in time trials is unquestioned. Pro teams spend thousands of dollars for wind tunnel research so they can determine the lowest and fastest position for their riders without compromising power. But they do it on bikes with long crankarms -- often even longer than normal.

Thanks to Martin’s new study, we now have new knowledge: Short crankarms allow a lower aero position
without compromising wattage output.

I mention M.P. because (back in the day, B.C.) they rode such huge gears, the thought was that the very long cranks,
gave them a rolling advantage, at least that was the thought, as I observed and was told from the competitors,
at the World M.P. Champs... behind the Harleys for the last time (as far as I know)
Hope that helps,
Cheers,
BrentonO
Have you got an online link for the above information?
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Re: Crank length

Postby brentono » Sat Jul 10, 2010 2:54 pm

Nobody, DYOR :wink:
At the Serotta International Cycling Institute Science Symposium, Jim Martin, Ph.D.,
from the University of Utah presented his study of crank length.
Myth and Science in Cycling: Crank Length and Pedaling Technique - Jim Martin, PhD.
During this provocative presentation, Dr. Martin will discuss several position and equipment strategies
to improve cycling performance and whether there is any scientific evidence that they actually meet
the stated objective of going faster.

http://www.serottacyclinginstitute.com/2008CyclingSciencesymposiumlectures.htm
And (below)- Here's a PDF link with much of the info...
http://www.plan2peak.com/files/32_article_JMartinCrankLengthPedalingTechnique.pdf
Jim Martin is a cycliing enthusiast, a bicycle racer, holds a PhD in exercise science
and an undergrad degree in mechanical engineering.
He's a professor at the University of Utah and is as august an academic on the subject of crank length as anyone.
Here's a paper of his on it...
http://www.ncbi.nlm.nih.gov/pubmed/11417428
That will get you started, and next you could even try "Google"
Good Luck :D
Cheers,
BrentonO
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Re: Crank length

Postby Nobody » Sat Jul 10, 2010 8:34 pm

Thanks BrentonO.

That PDF file was the most informative document on crank length and pedaling I've ever read. :D
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Re: Crank length

Postby brentono » Sun Jul 11, 2010 11:42 am

Nobody wrote:Thanks BrentonO.

That PDF file was the most informative document on crank length and pedaling I've ever read. :D


No worries, helps dispell a lot of myths that are floating around, hope many others may gain from it, as well :)
Cheers,
BrentonO
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