# Theory and practice...

Experience is nothing but history unless it affects your future. I’ve affected my future a bit today so I thought I’d share it with you.

A few weeks back, after detailed mathematical calculations, i decided I ‘needed’ 170 mm cranks on my 26 to match (or slightly beat) the leverage ratio of my 24. This was for the good reason that I was finding I could climb and descend steeper hills on my general purpose 24 than I could on my purpose-built Muni.

Today I noticed as I selected a uni for the evening’s ride that I was drawn to take the 24, even though I was planning to ride on some moderate off road and forest tracks. Sometimes our gut feelings tell us more than logic can.

So I took the 26 with the 170 mm cranks, and had a fairly mediocre ride. The control on descents is phenomenal, but I was struggling on ascents, and also finding the tracks to be narower than they looked. The fact is, the 170 mm cranks are that bit too long for comfort, and the extra 40 mm diameter on the pedaling circle makes for a jerky ride. (Several passers-by even remarked, ‘Did you see that jerk?’)

When I realised I had just struggled up a hill which would have been achievable on the Coker (with a leverage ratio much worse) I decided that the smoothness of medium/short cranks is more important than the maximum torque available from long cranks, except in the special case of extreme descents.

So, back home an on with the old 150 mm cranks, putting my hand in the dog droppings on the tyre as I did so ( Ugh! ) and out for a quick blast up and down the sloping carpark. It was like being reunited with an old friend.

So, the experience is that, never mind the mathematics, a crank length that allows a smooth pedaling action is more important. And if I find myself needing the leverage, I’ll achieve it by getting a decent off road 24.

This experience cost me 18 quid, so I estimate each reader of this thread will owe me about 10 bob.

I know at least one Bob that I would be happy to send you. It’s worth it to send you nine others just to get rid of this one. Where do I send them? Should I send a change of clothes with them?

Mathematics aside, if it feels good, do it! The calculations tell you what might be optimal. Sometimes they tell you cranks that are longer than your legs are optimal. It’s time to question the validity of the analysis at that point.

Re: Theory and practice…

Could other MUni’ers please comment on Mike’s observation? I was
planning to buy 170’s on my new MUni. Recently I switched 125 to 150
on my 24" and found it much better for rough terrain - but certainly
not for speed.

And Mike, were you kidding about DETAILED methematical calculations?
If not, I’d be interested to know what you did. I’ve been thinking a
bit about taking lengths of upper and lower leg (I mean tibia and
femur) into account, as well as seat height etc.

Klaas Bil

On Wed, 19 Jun 2002 13:48:52 -0500, Mikefule
<Mikefule.6idia@timelimit.unicyclist.com> wrote:

>
>Experience is nothing but history unless it affects your future. I’ve
>affected my future a bit today so I thought I’d share it with you.
>
>A few weeks back, after detailed mathematical calculations, i decided I
>‘needed’ 170 mm cranks on my 26 to match (or slightly beat) the leverage
>ratio of my 24. This was for the good reason that I was finding I could
>climb and descend steeper hills on my general purpose 24 than I could on
>my purpose-built Muni.
>
>Today I noticed as I selected a uni for the evening’s ride that I was
>drawn to take the 24, even though I was planning to ride on some
>moderate off road and forest tracks. Sometimes our gut feelings tell us
>more than logic can.
>
>So I took the 26 with the 170 mm cranks, and had a fairly mediocre ride.
>The control on descents is phenomenal, but I was struggling on ascents,
>and also finding the tracks to be narower than they looked. The fact
>is, the 170 mm cranks are that bit too long for comfort, and the extra
>40 mm diameter on the pedaling circle makes for a jerky ride. (Several
>passers-by even remarked, ‘Did you see that jerk?’)
>
>When I realised I had just struggled up a hill which would have been
>achievable on the Coker (with a leverage ratio much worse) I decided
>that the smoothness of medium/short cranks is more important than the
>maximum torque available from long cranks, except in the special case of
>extreme descents.
>
>So, back home an on with the old 150 mm cranks, putting my hand in the
>dog droppings on the tyre as I did so ( Ugh! ) and out for a quick blast
>up and down the sloping carpark. It was like being reunited with an old
>friend.
>
>So, the experience is that, never mind the mathematics, a crank length
>that allows a smooth pedaling action is more important. And if I find
>myself needing the leverage, I’ll achieve it by getting a decent off
>
>This experience cost me 18 quid, so I estimate each reader of this
>
>
>–
>Mikefule - Roland Hope School of Unicycling
>------------------------------------------------------------------------
>Mikefule’s Profile: http://www.unicyclist.com/profile/879
>

Re: Theory and practice…

In article <Mikefule.6idia@timelimit.unicyclist.com>, Mikefule <Mikefule.6idia@timelimit.unicyclist.com> wrote:
>
> So, back home an on with the old 150 mm cranks, putting my hand in the
> dog droppings on the tyre as I did so ( Ugh! ) and out for a quick blast
> up and down the sloping carpark. It was like being reunited with an old
> friend.
>
> So, the experience is that, never mind the mathematics, a crank length
> that allows a smooth pedaling action is more important. And if I find
> myself needing the leverage, I’ll achieve it by getting a decent off

i ride a 20" trials uni both for trials and off road and i’ll never look since i changed my 125mm cranks for 150mm, now i find that climbing hills is so much easier, and desents are much smoother, but alltogther slower.

the 150’s are as big as you can practicaly fit on a uni with an onza tyre,

the moral of the story is perhaps:
find out what size cranks you like before buying a splined hub.

UMX aka evil ewan

citizen_smith@hotmailOBSCURED.com
(your know the deal, there isn’t realy a domain called
hotmailOBSCURED.com)

Re: Re: Theory and practice…

It all depends on personal preference and the terrain you want to ride. But, for what its worth, I’ll just say that you can learn to ride smoothly with 170mm cranks. Its true they are kinda slow on the flat, but I find them to be worth it on technical terrain.

Ben

Re: Re: Theory and practice…

Long cranks on a muni take some practice to get used to, but once you get used to them they do really well. Longer cranks make it easier to get over roots, recover from unexpected bumps, maintain control on steep downhills, do a long climb. Climbing with long cranks requires that you learn a different rhythm and pedal in as much of a circle as you can manage. But once you learn the rhythm the long climbs are easier. Short cranks can have an advantage for short hills where you can get more speed and momentum with the short cranks to carry you over the hill. But when the hills get longer or technical then the long cranks will do better.

Without knowing the terrain and trails you ride it is hard to know if long or short cranks would work better for you.

john_childs

Re: Theory and practice…

Do any of you guys ride a 24x3 inch MUni with 175mm cranks?

-Dylan

Re: Re: Theory and practice…

Kidding. It was a simple case of comparing the length of crank to the radius of the wheel and expressing it as a percentage.
Thus, on a 20 inch wheel with 5 inch cranks, I produced 50%.
On a 24 with 6 inch cranks, it is also 50%

On a 26 with 6 inch cranks (my original set up) it is 6/13 = 46.15%

But, the difference is more than 50 - 46.15 = 3.85.
The increase in leverage from 46.15 up to 50 is the difference over the lower figure = 8.3% approx.

Thus, my 24 in standard trim had 8% more leverage than my Muni.

With this in mind, I calculated for 170 mm cranks and got a % of 52.3.

(With 175 mm cranks, a ratio of 53.8% would be achieved on a 26.)

Set against this, you lose fluidity of movement. I found I could bludgeon my way out of difficulty, but I was more likely to get into difficulty.

I guess the optimal crank length is related to the length of your legs. I’m of the petit persuasion (5’7" 170cm) , and with my seat a little bit low for off roading, and with big cranks, it felt like my kneess were about to hit my chin.

When standing on the pedals to go up hill, it is a bit like walking up a flight of steps, and for me the 170 mm cranks made those steps almost 14 inches high, and uncomfortable to climb.

Taller people may find 170mm optimal.

Another problem is that several times I got the pedals to hit the deck - something that seldom happened with the 150s.

RE: Theory and practice…

> When I realised I had just struggled up a hill which would have been
> achievable on the Coker (with a leverage ratio much worse) I decided
> that the smoothness of medium/short cranks is more important than the
> maximum torque available from long cranks, except in the
> special case of extreme descents.

Or ascents.

> So, the experience is that, never mind the mathematics, a crank length
> that allows a smooth pedaling action is more important. And if I find
> myself needing the leverage, I’ll achieve it by getting a decent off

I certainly never mind the mathematics. They only tell part of the story.
Mathematical calculations don’t remind you that you’re used to one
combination of wheel and crank size, and you’re just trying the new one for
your first time. You’re not being fair to yourself if you don’t give it
several rides to see if you get used to it.

Until recently, I’ve been using 150mm cranks on my 26" MUnis. They were fine
for me, except in technical or steep terrain, though I had “grown up” with
125mm cranks and only felt fluid and fast on them. But most of my MUni
friends would rib me about my short cranks.

Then Steve Howard sent me his aluminum prototype (the one that’s going to be
auctioned at UNICON), with a 24" x 3" Gazzaloddi tire (nominally 26"
diameter) and 170mm cranks. On my first ride with the cycle, I got lost in a
local park and ended up riding a bunch of pavement and smooth dirt to get
home on time. I really didn’t like the cranks. I couldn’t pedal fast without
bouncing up and down!

But I can now. Plus I knew it was possible anyway. I remember sprinting with
George Peck once, him on 175s and me on 150s. I assumed I could easily beat
him. I couldn’t. Over the short haul, I was not able to go any faster than
him. And, in national MUni races in 1999 and 2001, I watched Kris Holm pull
away from me and recede into the distance; him on 170 or 175s, and me on 140
(1999) and 150mm (2001) cranks.

This past Sunday, I rode the Downieville Downhill. We rode about 18 miles,
climbing 720’ and descending about 4900’. Ouch. It’s Thursday now, and I
only just have full use of my legs back. I put 150s on the Steve Howard
cycle, because I had remembered the trail as being mostly easy and
non-technical. I remembered wrong. Most of the first six miles of the ride
had lots of steep rock fields and other plenty-technical parts. Those 150mm
cranks were inadequate. My thoughts after that ride: 150 is too short for a
3" Gazz tire. Between the weight of the wheel and the type of terrain it
belongs on, you need more leverage.

So – here are the non-mathematical factors involved in all this (I might be
forgetting some):

• What you’re used to
• Rider height/leg length
• Steepness of terrain
• Difficulty of terrain
• Personal preference

Traditionally, I am used to 125mm cranks, as they were both on my racing and
freestyle cycles. It took me a long time to get comfortable with 150s on the
trail. Same thing when I went to 170s. I’m 6’ tall, so 170 is a bit less of
a stretch for me. You might also try an in-between size, like 160. Your
local terrain has a lot to do with it. The Sacramento area trails are
not-so-technical, though they have technical spots. But Santa Cruz and the
Sierra trails have a higher percentage of technical areas per ride. I have
to choose a compromise, or have the wrong sort of cycle for part of each
ride. I’m going more toward the technical, because it’s still a challenge
whereas the easy trails are not.

Lastly, personal preference. For this, you have to give yourself a chance
and see if your body adjusts to the new sizes. One ride is not enough to
tell. I would have thought the same thing when I first rode on those 170s.
But I realized it was not a typical ride (trying to hurry back on pavement),
and I had the experience of watching the MUni masters on their long cranks.

My own new MUni, a Wilder, which I had ordered before Steve Howard offered
me his, will come with either 160 or 165mm cranks (I forget). I’ll see how
those work out…

Stay on top,
John Foss, the Uni-Cyclone
jfoss@unicycling.com
www.unicycling.com <http://www.unicycling.com>

“This unicycle is made all from lightweight materials. But it uses a lot of
them.” – Cliff Cordy, describing the very heavy new prototype unicycle he
brought on the Downieville Downhill

John Foss remarked that one ride is not enough to decide, etc., and I agree. But…

I have ridden with the 170 mm cranks on numerous occasions, including favourite local flat-but-bumpy tracks, downhill tracks in the forest, and medium distances (5 miles without stopping at all as part of a longer ride) on flat gritted towpaths.

My local bit of bumpy forest is a regular stamping ground for me, and the first time I went there, I rode all the way up the first hill in one go on the Muni with 150s. I have not managed that since I fitted the 170s! It feels like they are simply too long for my short legs - strange as I’ve bicycled and tandemed thousands of miles on 170 mm cranks. It just doesn’t work for me on the Muni.

As I said in the first post on the thread, I went into my room where I keep my fleet of unis, and I found myself strangely drawn towards the 24. Strange as the Muni was once my pride and joy, and the 24 is only a basic Nimbus 1 with a slightly beefier tyre.

Were I not such an introspective person, I would simply have picked up the 24 and gone on my ride, but being introspective, I thought, ‘Why don’t I want to choose the Muni any more?’ Then I forced myself to take the Muni, thinking I was being silly, and throughout most of the ride, I knew I’d have been happier on the 24.

As soon as I put the 150s back on the Muni, it felt right again. So I might lose some torque and have to walk a bit more, or perhaps I’ll slip the 170s on for certain types of ride. NONE OF THIS MATTERS except that I thought I’d publicise my experience which might help someone else out there who could be misled into thinking that longer cranks would be all advantages and no disadvantages. There are pros and cons, and the balance between these will vary from rider to rider, and terrain to terrain.

(I wonder what it is about me that makes me so introspective.)