## bad knees with 20" or 24"

### bad knees with 20" or 24"

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.

Rod Wylie

### bad knees with 20" or 24"

Rod,

Knee problems are found with unicyclists as well.  Be sure you have your
seat at its correct height and not too low.

Your assumption about the gearing is not quite correct.  To calculate the
gearing comparison between a bike and unicycle you need to calculate the
force applied at the pedal for a given movement of the wheel then you will
be able to compare one with the other.  Unicycles are geared by changing the
length of the cranks and hence the force/distance moved ratio.

Roger

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Quote:
----- Original Message -----

Sent: Monday, April 09, 2001 7:46 AM
Subject: bad knees with 20" or 24"

> 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.

> Rod Wylie

### bad knees with 20" or 24"

There is a good analysis of pedal forces for different wheel size and crank
length combinations at
http://www.sports-psych.com/muni/wheeland.htm

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

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.

john_childs

Quote:

>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.