There is a good analysis of pedal forces for different wheel size and crank
length combinations at
One thing that is different in pedaling a unicycle than a bike is that on a
unicycle you need to backpedal to maintain balance and slow down. This
backpedaling uses different muscles and puts different stresses on the knee.
To minimize knee stress on a unicycle make sure that the seat is not too
low. Figuring out seat height is very similar to figuring seat height on a
bike. Hold on to a wall and put both heals on the pedals. Pedal a few
revolutions while using the wall for balance. If the seat is too high your
hips will rock as you pedal. You want the seat as high as you can without
causing your hips to rock.
20" vs. 24" depends on how you intend to ride. The pedal forces on a 20"
with 125mm cranks will be about the same as a 24" with 152mm cranks. But
keep in mind that longer cranks mean that your knees will bend more which
can put more strain on the knee (especially if you have IT band problems).
If you want to cover any distance, walk the dog, etc. a 24" would be better.
If you want to just goof around in a parking lot and practice tricks then
a 20" might be better. For general all round flexibility a 24" is better.
>Anyone have any advice as to what I should by as a first Unicycle. I
>have worn out knees from earlier bike touring days. I am learning on a 16"
>and this seems fine, but it is plastic. Is 20" or 24" significantly
>different as far as the effort needed. What about getting into simple
>hills. Seems like a 20" rotates 60 inches in one revolution. That's a big
>gear for me when I use 27" on my mountain bike.
>Anyone got any advice.
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