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Crank Arm Lengths
After recently suffering from a sore knee on most rides I have been looking at cleat positions, seat fore/aft adjustments etc when I came across a few articles on crank lengths. While there seems to be a few theories on working out the correct length they all end up saying it is trial and error.
My current bike has 175mm cranks and it looks like 165-170mm would be better suited. Has anyone changed cranked lengths and had a noticeable difference.
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Are you looking for the different crank lengths to alleviate your knee pain? I would have thought that the shorter length crank resulting in reduced mechanical advantage (therefore requiring extra muscular exertion to turn it over) might cause more pressure on your knee.
Of course it would cause fewer hits on stray rocks!
What has the physio said the knee pain cause might be?
My knee was a lot better after adjusting my cleats so this is not just for knee pain but I do want to make sure nothing is contributing to bad knees. With the theory of less leverage this is more an issue with single speeds. Having gears means I may end up in just a different gear to what I would normally use.
I was thinking that lets say with a crank 10mm shorter means I would have to raise my seat to keep the same distance between my seat and the pedal at bottom dead centre (6 o'clock position). Now with the combination of my seat being higher and a shorter crank at top dead centre (12 o'clock position) my knee would be at less of an angle so the range of motion would be less and potentially less stress on my knees.
You won't need shorter cranks unless you are very short.
Knee pain on bikes is caused by bad seat height and/or position and bad cleat position. So address those. I've also heard of some who just didn't get on with their bike and when they got a new bike the knee pain vanished. However this is rare. And perhaps you are pushing to high a gear. A high cadence is a good thing.
and go and see Steve Hogg at Cyclefit (http://www.cyclefitcentre.com/). He'll sort you out..
... or not, as in my case.
I am such a basket case that he's sent me to a manipulative physio who is and knows about cycling to get straightened out first.
The physio called me "complex". I think that's probably a euphemism for "a mess". Hopefully in about 12 weeks or so I'll be sorted out enough that Steve and I can take up where we left off.
Money well spent.
There was an excellent article about knee issues in last month's "Dirt Rag"
Check it out:
http://www.dirtragmag.com/print/article.php?ID=1...