What is the best way to determine the correct crank length for my height and more specifically my leg length?
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2i believe it also depends on the bike/frame type. For example on fixed-gear bikes used for commuting you would use shorter cranks then on free wheel, to avoid hitting road/curbs etc when taking corners– kristofCommented Sep 3, 2010 at 14:28
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2 Answers
This is probably going to depend on a bit more than just your height or leg length (though I'm sure a rough idea can be gleaned). Your specific bike (geometry) and riding position will also affect crank length a bit.
Here are a few good links on the subject that go beyond my knowledge on the issue.
answered Sep 3, 2010 at 16:31
I disagree with the selected answer as most of the provided links are simply opinion without any analytical backing.
In terms of choosing a crank length on the basis of performance, there is very little scientific support for there being any real discernible differences widely used crank lengths (160-180 mm).
For an overview of some of the scientific results, see this set of PowerPoint slides:
http://www.plan2peak.com/files/32_article_JMartinCrankLengthPedalingTechnique.pdf
As well, a good summary of the science, in a readable format, is available on the Cervelo website:
http://www.cervelo.com/en/engineering/ask-the-engineers/crank-length.html
Note that in terms of peak power output power output Martin and Spirduso (2001) found no significant difference between crank lengths of 145, 170 and 195mm.
This leaves the choice more as personal preference which may entail a number of details from fit to riding style and comfort.
Other SE questions covering this subject.
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This answer is a duplicate of the one you link to. Link-only answers are not very useful. Please edit your answer to include enough information that it can stand alone, with the links as references backing up your actual answer. It also contradicts this answer (referenced): bicycles.stackexchange.com/questions/23352/…– MóżCommented Aug 7, 2014 at 23:21
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No scientific support? Personal preference? Would you put 175mm cranks on a bicycle for a four-year-old? For a hamster?– KazCommented Jul 15, 2016 at 18:40
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2@Kaz - you are using a straw man argument. If you read the answer we are talking about crank lengths for healthy adults and over the range of commonly used sizes 160-180mm. In this context there are little measurable performance differences. This doesn't comment on edge cases such as adults with hip mobility issues or other benefits such as being able to pedal through a corner.– Rider_XCommented Jul 15, 2016 at 18:49
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It's not unheard of for adults to be as small as 4'11" or as tall as 6'6". Would you give the 160mm crank to the 6'6" person, and the 180mm to the 4'11" person?– KazCommented Jul 15, 2016 at 19:31
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3@Kaz - The take home message from the research the crank length that comes spec'd on the bike will be fine for most people (i.e., there will be little discernible gains changing +-5mm). Now if you want to misconstrue this and get lost in edge cases, that is your choice. But for the record I would be more concerned about running too long a crank (i.e., 180mm crank for someone 4'11") than a shorter crank (i.e., 160mm crank on a 6'6" person) due to potential hip flexibility issues. On the track someone 6'6" may actually want 160 mm crank length to improve turnover rate.– Rider_XCommented Jul 20, 2016 at 18:00