crank comparisons

Crank comparisons.

The story so far...

After over a year of riding a 24x3" muni with 150mm cranks, mainly for
getting around town and mild muni stuff; I fit my little used 28-er with
a fat tyre.

The comfort of the new tyre distracts me from the loss of control that
comes with 125mm cranks and after a few weeks I find myself quite
competent on the 29-er with 125's.

So much so that I order some 110's from unicycle.com.

The first ride with these I find myself feeling a little unstable and
have difficulties on hills, especially downhills.

Today I went out for the second time and things were a little
improved.

However, my impressions are that I'm not percieving any noticable
improvement in speed or smoothness and that steepish hills are
impossible. I also wonder if any improvement in speed would be offset by
the loss on hills and in the extra messing around getting balanced after
minor bumps etc.

Since this is only the second ride there's a good chance that these
problems will dissapear with more practice, I'm aware that I felt much
the same way going from 150's to 125's, but now I can definitly
appreciate the good points of 125's.

I'm in a no lose situation because, as xxxxx pointed out, if I decide to
switch back from the 110's to 125's, they're going to feel very
controlled.

Having read other posts on the subject I suspect I may well switch back,
especially as I live in hilly Sheffield and as I like to go off the
roads into a bit of mild muni stuff. However I intend to stick with the
110's a while so I can form valid conclusions.

Getting back from the ride I decided to take my neglected 24x3 muni
out.

The difference in the turning circle of my legs after 125/110's was
vast, I could ride ok but my thighs were really having to shift.

Given the mass of human thighs I now understand why riding a muni
involves so much sweat, I reckon as much energy must be used in simply
lifting and lowering the knees as goes into forward motion of the uni.

On the good side that should make muni riding good for exercise.

I also noticed that there had been no saddle soreness on the 29-er, but
a noticable amount really early on with the muni- not massive but the
start of something that would be a factor in an hours time.

It occured to me that the large leg turning circle of the muni may lead
to more chaffing than on 28/29-ers with smaller cranks.

Half way through I encountered a tricky bit that would be impossible on
the 29 and suddenly remembered what the muni was for!

The rest of the ride involved bouncing over rough stuff and going up and
down really steep hills; I arrived home drenched in sweat.

I would like to ask a question of those who've ridden both long and
short cranks- do you reckon that shorter cranks are better for saddle
comfort given that there is less rubbing of the inner thighs on the
saddle?


--
onewheeldave - Semi Skilled Unicyclist

"He's also been known to indulge in a spot of flame juggling - but it's
the Muni that really fires him up."

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The friction thing has to be lower with short cranks. But other than
that, crank length is a relatively minor part of saddle comfort.

Danny sounds like he doesn't have a good "spin" on his longer cranks,
causing him to bounce up and down. This can be hard to damp out with
real long cranks at high speeds.

Saddle comfort can be controlled much better with a good pair of shorts,
a handle or handlebar, and experimentation to find the type/brand of
seat that works best with your own personal... crotch. There is no
definitive "most comfortable" seat, because different people like
different ones.


--
johnfoss - Now riding to work

John Foss
the Uni-Cyclone
www.unicycling.com
________________

"Where's my kids?" -- Amy Drummond
"Where's my unicycle?" -- Andy Cotter
spoken one right after the other, mostly to themselves, at NAUCC 2003

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Tadaaaaaaa! Mikefule takes the bait...

125s are 17% shorter than 150s.

110s are 12% shorter than 125s.

Thus the step from 125 to 110 is smaller than the step from 150 to 125,
so the change should be easier.

But 110s nare 27% shorter than 150s, so that's a major difference.

Adjust your seat height carefully. At first sight, 110s are 15 mm
shorter than 125s, so it would be tempting to raise your seat by 15mm
because the pedal is 15mm higher at the bottom of its travel. However,
I find there is a general tendency that as cranks get shorter, the
amount of seat adjustment decreases. I can't say more except to warn:
do not assume that the standard 'leg straight, heel on the pedal at the
bottom' is the perfect seat height.

The advantages of short cranks are two:

When cruising on the flat, you can maintain a higher cadence
comfortably.

When really going for it, you can hit a higher maximum cadence.

The disadvantages are

Mounting needs more precision

Idling needs more care

Stopping is trickier

Uphills are harder work

Downhills are dodgier.


Practice will improve all of these things. I have ridden reasonably
challenging off road on a 28 with a skinny tyre and 110s, and a 24 with
102s (or even 89s).

But there is no sense in going for the shortest cranks you can manage.
You need to get used to the feel of the cranks, and learn to feel 'at
home' on the uni. You need to learn the little tricks of timing, and
when to fight and when to let the uni have its head.

The downhill problem is that the shorter cranks allow the pedals to
flick past the point of no return much more easily.

I strongly recommend that you persevere with the 110s. On a 28 or 29,
they are a fine size for fast smooth riding. 125s for more challenging
stuff, possibly. A good handle is worth 10% or more on the length of
your cranks.

As for seat induced discomfort, I find that shorter cranks encourage a
faster cadence, and this seems to translate into a slightly more mobile
lower anatomy, so generally, I get less pressure pain. Chafing
shouldn't be a problem if you wear the right clothes, and you're not
ashamed to adjust your cargo manually.


--
Mikefule - Roland Hope School of Unicycling

"Our greatest glory is not in never falling, but in rising every time we
fall."
Confucius
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On Thu, 28 Aug 2003 15:40:18 -0500, onewheeldave
wrote:

I would like to ask a question of those who've ridden both long and
short cranks- do you reckon that shorter cranks are better for saddle
comfort given that there is less rubbing of the inner thighs on the
saddle?

Thanks for the write-up. I'm onto the same as you.

As for the question above: I used to be a victim of rubbing/chafing
until I switched to wearing cycling shorts exclusively (on the uni,
that is). So now I have no chafing whatsoever, on any crank size.
Klaas Bil - Newsgroup Addict
--
I go a sort of ok speed on my Coker... - Roger Davies

Mikefule wrote:
*...
Adjust your seat height carefully. At first sight, 110s are 15 mm
shorter than 125s, so it would be tempting to raise your seat by 15mm
because the pedal is 15mm higher at the bottom of its travel.
However, I find there is a general tendency that as cranks get
shorter, the amount of seat adjustment decreases. I can't say more
except to warn: do not assume that the standard 'leg straight, heel on
the pedal at the bottom' is the perfect seat height.
...
*

I switched from 150s to 110s a few weeks ago, and after some
experimentation I've settled on a seat hight which is actually lower
than before. Basically I was impatient with the slowness of the 150s,
and had the seat unnaturally high to reduce knee/thigh bounce.

In terms of control, for me the key with shorter cranks is patience.
With 150+ cranks I can correct most any balance problem in a pedal
cycle. With 110s, I sometimes need to solve 70% of the problem in the
first cycle and save 30% of it for the next one. The tempation is to
take an easy UPD at t=0 rather than risk a harder one at t=2.


--
cjd - who dat?
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anybody ever make a saddle shaped like a donut? that sound like it'd be
comfortable


--
ubersquish
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ubersquish wrote:
*anybody ever make a saddle shaped like a donut? *


On what axis?

A huge donut shaped saddle with the axis horizontal and parallel to the
wheel axle would be comfy for the rider to sit inside. He or she could
lean backwards against the inside curve of the donut to relax on the
cruising sections. In the case of a forward UPD, or a falling tree
branch, the donut shaped saddle would provide good rider protection. On
the other hand, the rider wouldn't be able to see where he or she was
going.


--
Mikefule - Roland Hope School of Unicycling

"Our greatest glory is not in never falling, but in rising every time we
fall."
Confucius
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on what axis? man, how do you eat -your- donuts? vertical, like those
things you sit on after getting butt surgery. except you sit further
back on it than that, since it's not your bum that goes over the hole


--
ubersquish
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johnfoss wrote:

The friction thing has to be lower with short cranks.

What's a friction thing? Can you please be more specific?

But other than that, crank length is a relatively minor part of saddle
comfort.

Ignoring the "But other than that," part of this sentence:

"crank length is a relatively minor part of saddle comfort."

Crank length has nothing to do with saddle comfort, except for two
things:

1) The upper inner thigh rubs back and front against the seat less with
a shorter crank (smaller circular movement of the foot) than with a
longer crank (larger circular movement of the foot).

2) Greater force must be applied to the pedals when attached to shorter
cranks versus when attached to longer cranks. This force must be
subtracted from the rider's weight (force) to get the net weight
(force) being applied down on the seat. Seat comfort is related to
that fraction of the rider's weight that rests on the seat. The
cranks can be easily made short enough to reduce that weight to
zero (the rider must apply his full weight on the pedals to ride).
Clearly, with very sort cranks, crank length is a _major_ factor
(almost only factor) in saddle comfort.

Sincerely,

Ken Fuchs

The friction thing was indeed the extra thigh rubbing which comes from
the extra thigh movement with longer cranks.

My opinion is that it is a factor cos most of my saddle pains have been
from chaffing rather than pressure ones (which would be affected by your
point no. 2)

no.2 is interesting, I'd never thought of that.


--
onewheeldave - Semi Skilled Unicyclist

"He's also been known to indulge in a spot of flame juggling - but it's
the Muni that really fires him up."

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