Crank Length VS. Height and Weight or Does Size Really Matter?

Ok, lets talk about the size of our cranks. Seriously...

I was wondering how the height and weight of a rider would effect
what the optimum crank length would be. I've heard some distance riders
saying that a 125mm or shorter length is optimal even for climbing
fairly significant grades. I wonder if this would remain true for a
rider like myself who is 6'3" and 200 lbs. For me when I was road
riding daily I still felt more comfortable with 150mm cranks (I ride a
fairly hilly course). The length helped me both acending and decending.
A guy who was say 150 lbs might benefit from short cranks as he has less
weight to push up the hill and less weight to hold back decending. I
think the same would hold true for Muni.

Please add your thoughts.

-Phil


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I think if your going weight:length then it may be the opposite, with
more weight you have more pressure so you don't need additional
leverage from longer cranks. I like cruising around town on 150s on my
36er but for going fast I like short cranks (125) because its easier
for my stubby legs to spin.


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I think rider strength and technique are of far more significance than
rider weight and height when it comes to optimum crank length, which
also might changes over time as strength and technique develop.


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I think technique is the more important of the two, especially if you
ride with a brake as I do. Because of my injuries my muscles tend to be
out of shape, but I can still do great riding because of my technique.
Muscles are good for climbing (ewww), and slowing down (which I have a
break for (why would you want to slow down)).


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pdc wrote:
Ok, lets talk about the size of our cranks. Seriously...

I was wondering how the height and weight of a rider would effect
what the optimum crank length would be. I've heard some distance riders
saying that a 125mm or shorter length is optimal even for climbing
fairly significant grades. I wonder if this would remain true for a
rider like myself who is 6'3" and 200 lbs. For me when I was road
riding daily I still felt more comfortable with 150mm cranks (I ride a
fairly hilly course). The length helped me both acending and decending.
A guy who was say 150 lbs might benefit from short cranks as he has less
weight to push up the hill and less weight to hold back decending. I
think the same would hold true for Muni.

Please add your thoughts.

-Phil



In the bike world, taller riders use slightly longer cranks and smaller
riders use shorter cranks. The length only varies by about 5mm though.
It is obviously a bit different in the unicycling world, but I think
that smaller/lighter riders will have an easier time with shorter
cranks.

Your area is indeed hilly, and for the climbing the 150s are going to
feel easier for you. I would stick with that length knowing your
terrain and experience. You might want to try some 140mm cranks out
though. I have some Schlumpf 140mm aluminum cranks to use specifically
for the Shenandoah region. I think that is the ideal size for Skyline
Drive, even though I have yet to try them out! I am not sure if there
are other 140mm squar taper cranks out there that are lightweight and
of decent quality, but it may be worth it to order a pair of the
schlumpf 140s.


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The torque/weight ratio is constant for -all- riders using -any one-
crank length as long as the weight of the unicycle is insignificant.
Torque advantage comes with increasing crank length and decreasing
wheel diameter for all riders. I like long cranks because I have long
legs and don't have as much of an exaggerated pump stroke when I pedal
as someone with stumps. That is, I can get away with it so why not go
with the torque advantage? I even put 170's on Blue Shift...but Phil
already knows this.


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I came here to say what Harper said.

If you're a tall person with long legs you'll have an easier time with
longer cranks. Your knees won't move up as high or be as exaggerated
compared to a shorter person.

If you're tall and can get away with it, take advantage of it. Use
longish cranks if you can spin them smoothly and still "dance" on them
while climbing.

I have long legs for my height. I have been comfortable on longer
cranks than other people. I like the advantages I have with longer
cranks for the riding that I do and riding the way I like to ride.
That's all that matters.

If you have poor spinning technique then climbing with cranks that are
too long can actually hinder you. Poor technique can cause you to get
stuck and lose momentum at the bottom of the stroke, especially when
standing out of the saddle while climbing. The comment about "dancing"
on the pedals was a reference to that. If you can dance and keep the
pedals going without dwelling at the bottom of the stroke then you're
good. If you can dance on the pedals without causing your whole body
to bob up and down excessively you're good.

Shorter people (or people with shorter legs) will have a more difficult
time dancing on the pedals with longer cranks. When the cranks get so
long that you can't dance properly then the long cranks become a
hindrance rather than a benefit.


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I really can't get on with short cranks on my coker. I tried 125s for a
bit before unicon, because it was "the thing to do" for flat riding
(Denmark), but after 100 miles or so I went back to the trusty 145s.
I'm not a huge spinner (my max speed is usually about 16mph), so
perhaps longer cranks suit me better. The 125s just made freemounting
more difficult and didn't seem to have any advantage for me - my top
speed was actually slower because of lack of control. Perhaps I didn't
stick at it for long enough. Also, the short stroke of the 125s just
feels very inefficient to me, wasting muscle range and putting needless
extra pressure on the knees. Most other people seem to think they're
fantastic though, and all the fastest riders favour small cranks, so
presumably it's not just "emperor's new clothes".

I'm just under 6' 2", and weigh 12st (168lbs).

BTW: I think my top speed on the coker is limited more by lack of guts
than ability to spin. I can spin faster on the 26" muni with 150s, but
obviously at a lower speed so it doesn't feel so dangerous.

Rob


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I don't know that there's any correlation between height and preferred
crank length. I've seen riders of a wide range of heights with a range
of cranks lengths on 36ers around here, on the road and off the road, up
and down hills.


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