Best crank size for 12" sem

Unicycles and Equipment
1

My 5 yr old just started learning on a 12" sem which came with 4" cranks
from unicycle.com. (John - it’s great).

They lower pedal is 1/2 inch from the ground when the cranks are vertical,
meaning, he can’t lean right or left. I think this is hindering him a bit
in the learning process.

For this wheel size and age, these cranks are LONG. I can ride his 12" in
a straight line, but to turn I cannot lean, but instead must do a
standstill, then rotate my body along a vertical axis. (Talk about circus
clowns!) Of course for a beginner, this is impossible.

When my son attempts to ride, a pedal will hit the ground and knock him
off balance. He doesn’t want anyone holding his hands, he just wants to
get on it and keep trying. I’m sure his persistence will pay off, but I’m
wondering if he might be better off with 3 or 3.5 inch cranks (assuming
they are available).

Anyone else out there have kids riding the 12" sem?

Joe

2

My Scout troop has a 12" Sem. We have the same problem, although a few of
the guys can turn by leaning. They seem to do it by straightening up the
wheel when the inside pedal is down. It isn’t smooth it’s:
turn-straight-turn-straight-turn, but it also isn’t squaring to direction
you want to go and then jerking the uni around . Of course we only use the
12" uni for fooling around, and not for learning to ride on. I have taught
younger kids to ride on a 16" uni without this particular problem. Could
your son fit on a 16" uni?

As I recall the 12" Sem XL came with 110mm cranks (about 4.3") which I
replaces with 102mm cranks (4") that I got from Unicycle Source. I’m sure
the 8mm difference helps. You might want to check the length carefully and
switch to 102’s if they are 110. At Unicon X many of the Japanese
freestyle riders rode 20" Miyatas with tiny cranks, I think they were 98mm
or something like that. The short cranks helped with spins and really
smooth one foot skills, etc. I checked with John Drummond, he didn’t have
any. He said he would look into getting some. I’m sure they would help.

John Hooten

Nycjoe@aol.com wrote:

> My 5 yr old just started learning on a 12" sem which came with 4" cranks
> from unicycle.com. (John - it’s great).
>
> They lower pedal is 1/2 inch from the ground when the cranks are
> vertical, meaning, he can’t lean right or left. I think this is
> hindering him a bit in the learning process.
>
> For this wheel size and age, these cranks are LONG. I can ride his 12"
> in a straight line, but to turn I cannot lean, but instead must do a
> standstill, then rotate my body along a vertical axis. (Talk about
> circus clowns!) Of course for a beginner, this is impossible.
>
> When my son attempts to ride, a pedal will hit the ground and knock him
> off balance. He doesn’t want anyone holding his hands, he just wants to
> get on it and keep trying. I’m sure his persistence will pay off, but
> I’m wondering if he might be better off with 3 or 3.5 inch cranks
> (assuming they are available).
>
> Anyone else out there have kids riding the 12" sem?
>
> Joe

3

> My 5 yr old just started learning on a 12" sem which came with 4" cranks
> from unicycle.com. (John - it’s great).

I think 4" is pretty long for a 12" wheel. I don’t know how long the
cranks are on my own 12" unicycle, but they must be shorter. The pedals
still hit the ground when I turn, but I know there’s at least 1" clearance
after I sit on the uni and the tire compresses.

> meaning, he can’t lean right or left. I think this is hindering him a
> bit in the learning process.

It may not be too bad for learning to ride forward, but it is if it keeps
knocking him off. Regardless of rider size/weight, I think you want
shorter cranks.

> a standstill, then rotate my body along a vertical axis. (Talk about
> circus clowns!) Of course for a beginner, this is impossible.

Actually beginners usually turn using action-reaction in a relatively
clownlike motion (flailing). But still you need enough pedal
clearance to lean.

My 12" was made by Tom Miller from a disassembled, high-end children’s
bike. This gave me a decent rim with adjustable spokes, a real three piece
cottered crankset (Tom had to make the hub), and some juvenile pedals. The
little pedals are narrower than adult-sized pedals, so they increase the
lean angle before they touch the ground. You could try getting some
smaller (narrower) pedals as a temporary fix. But the closer your pedal is
to the ground in the first place, the less difference this will make.

Since this is a low-stress unicycle (even an adult probably won’t be doing
curbs on it), if you can’t find shorter cranks you can probably get them
cut and welded back together. I’m sure they will last the lifetime of the
cycle unless your son grows up to be Dan Heaton or Adam Rysnar… :slight_smile:

Stay on top, John Foss, the Uni-Cyclone jfoss@unicycling.com
www.unicycling.com

“Someone who thinks logically is a nice contrast to the real world.”

4

> My 5 yr old just started learning on a 12" sem which came with 4" cranks
> from unicycle.com. (John - it’s great).
>
> They lower pedal is 1/2 inch from the ground when the cranks are
> vertical, meaning, he can’t lean right or left. I think this is
> hindering him a bit in the learning process.
>
> For this wheel size and age, these cranks are LONG. I can ride his 12"
> in a straight line, but to turn I cannot lean, but instead must do a
> standstill, then rotate my body along a vertical axis. (Talk about
> circus clowns!) Of course for a beginner, this is impossible.
>
> When my son attempts to ride, a pedal will hit the ground and knock him
> off balance. He doesn’t want anyone holding his hands, he just wants to
> get on it and keep trying. I’m sure his persistence will pay off, but
> I’m wondering if he might be better off with 3 or 3.5 inch cranks
> (assuming they are available).
>
> Anyone else out there have kids riding the 12" sem?

Recently somebody in the twin cities made a 12" to fit a very small
little girl. My dad made some 3" cranks for it. I think they seemed to
work ok from what I could see(I wasnt allowed to ride it).

-Max A. Dingemans
5

On 6 Jun 2001 14:36:26 -0700, john_foss@asinet.com (John Foss) wrote:

>I think 4" is pretty long for a 12" wheel. I don’t know how long the
>cranks are on my own 12" unicycle, but they must be shorter. The pedals
>still hit the ground when I turn, but I know there’s at least 1"
>clearance after I sit on the uni and the tire compresses.

Your *-ing out the word “after” makes me wonder how much clearance there
would be during your sitting on the uni.

>“Someone who thinks logically is a nice contrast to the real world.”
I’ll take that as a compliment today :slight_smile:

Klaas Bil

“To trigger/fool/saturate/overload Echelon, the following has been picked
automagically from a database:” “crack, USS Harry S. Truman, FBI”

6

Joe,

You can get 102 mm cranks from Unicyclesource that will give you more
clearance. Many freestyle riders in Japan ride with 98 mm cranks. These
would be even better. A few weeks back Andy Cotter posted a link to a
japanese site where you can buy 98’s. I seem to remember that he bent the
127’s he bought there, but I doubt your 5 year old will have that problem.

John Hooten

Nycjoe@aol.com wrote:

> My 5 yr old just started learning on a 12" sem which came with 4" cranks
> from unicycle.com. (John - it’s great).
>
> They lower pedal is 1/2 inch from the ground when the cranks are
> vertical, meaning, he can’t lean right or left. I think this is
> hindering him a bit in the learning process.
>
> For this wheel size and age, these cranks are LONG. I can ride his 12"
> in a straight line, but to turn I cannot lean, but instead must do a
> standstill, then rotate my body along a vertical axis. (Talk about
> circus clowns!) Of course for a beginner, this is impossible.
>
> When my son attempts to ride, a pedal will hit the ground and knock him
> off balance. He doesn’t want anyone holding his hands, he just wants to
> get on it and keep trying. I’m sure his persistence will pay off, but
> I’m wondering if he might be better off with 3 or 3.5 inch cranks
> (assuming they are available).
>
> Anyone else out there have kids riding the 12" sem?
>
> Joe

7

102 mm are 4", which is what he already has. At the MYS site, they sell both steel and aluminum 89 mm (3.5") cranks, which are their shortest cranks.

That’s at: http://www.mys-co.com/cgibin/cgibin/shop.cgi?gcode=928