Big Wheels, Long Cranks...

Previously it's seemed that, with big wheels and distance, shorter
cranks are preferred, or seen as something to aspire to, as they make
for a smoother ride, faster cruising speed and faster max speed.

I've done a lot of riding on a muni (24x3) with 150mm cranks, and a fair
period (around 2/3 months of consistent daily riding, some months back)
on my 29=er with 125mm cranks.

Sheffield is very hilly, and most of my 29-er routes avoided the steep
road hills that I ride on my muni.

I slipped out of riding the 29-er, for the following reasons: -

* firstly, it's a bit of a road machine, being good for the roads and a
little dodgy on sidewalks; yet, to me, if you're on the roads you should
be 100% confident, and, on the 29 with 125s, I wasn't always that
confident

* it seemed to need regular practice to get the most out of it, and to
be safe on the roads; whereas the muni didn't suffer if I had a lay
off

* though, with that consistent practice, I felt OK on the 29-er; I found
that, when tired, it could be a bit dodgy and, like I said before, some
of the hillier regions were not practical

to elaborate, I'm sure that many of those hills were possible to get up,
but not in the sense that you could guarantee success, and not in such a
way that you'd be in much of a state to do much else afterwards.

Given that my 29-er riding was on roads, I think it's very important to
be 100% confident of staying on the thing under all circumstances,
otherwise I'm a danger to motorists.

So, as soon as my 29-er rides became less than daily, I found myself
slipping into communting on the muni again.

-----------------------

Till a few days ago when I read: -

http://tinyurl.com/7yhad

a post about a pretty hardcore Coker ride which, unusually, used 170mm
cranks, with great success.

It inspired me to switch my 150s onto the 29-er and see how well it
worked.

I did 2 rides yesterday and really liked them; another two rides today
have added to my feelings that 150's on a 29-er are possibly the ideal
combination for my situation; here's why: -

* instantly at ease on the road- a 29-er with 150's seems in between the
muni (a doddle to mount and ride) and the 29/125 (not 100% on mounting
and not the same certainty of staying on over rough stuff).

The characteristic 'momentum/flywheel' effect which kicks in on mounting
Cokers and 29-er/125s, is lacking with the longer cranks.

* security, despite it being months since riding a 29" wheel, I felt
totally safe on the road, even dismounting at a red light and remounting
when it changed, something I would not have felt happy about doing with
125 mm cranks

* speed, obviously it goes a fair bit faster than the muni. Additionally
though, in one sense it also beats the 29-er/125 combination. This is
because with 125's, I often felt disinclined to approach max speed
because it felt dangerous.

With 150's today I was happy pushing it

To illustrate- previously I'd recorded my time over a certain distance
with the 29/125 and repeated with the muni.

On the 29/125 it took 10 minutes; I was surprised to do it only a minute
slower (11 mins) on the muni.

I put it down to the aforementioned effect of being able to stay at max
spinning speed on the safe and secure muni, whereas on the 29-er there's
some holding back.

Today, on the 29-er with 150mm cranks I did the same course in 9 mins 15
seconds.

--------------------

Obviously there's a lot of factors here, my part of Sheffield really is
incredibly hilly, i probably am more cautious than many when it comes to
being on the road.

I also have no doubt that there are many on this forum who could 'whip
my ass' on these hills with big wheeled/short crank combinations.

However, for me, I'm very inspired by this 29-er/150 crank combination,
I think it's going to be the start of another big 29-er phase for me.

I've also found the 29/150 to be a superb XC muni machine (ie muni with
focus on speed and distance rahter than technical stuff).

Also, previously I've assumed that a getting a Coker to use in Sheffield
is not a practical possibility, due to the hills and traffic, however,
I'm now wondering if sticking some 170s or 175s on would tame it to the
extent that it would work here?

--------------------

So, I've posted this for two reasons-

1. To suggest to anyone that's got a big wheel with 'standard' cranks
(ie 28/29 with 125's or Cokers with 150s) and feeling a bit out of their
depth, whether it's because of the hills or excessive UPDS when they get
a bit tired; if you're on the verge of giving up, consider going up to
the next crank length and see how that works out

2. To do a poll to see if it's really the case that big wheelers use
short cranks, or are there some who actually prefer longer ones?


--
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 poll I posted hasn't surfaced

So I'll ask it he -

For big wheel riders (28/29/coker)

Do you use standard or shorter cranks, which I guess will be 125's or
less on a 28/29 and 150's or less on a coker

or

do you use longer cranks ie 150+ on 28/29 and 170+on a coker



For anyone who does use longer, it would be interesting to hear their
views and experiences (also of course for short crank users, it's just
that the pluses of short crank are fairly well known).


--
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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Interesting post, although it doesn't match my personal experience. I
recently switched from 150s to 140s on my coker, and I have only noticed
a couple changes.

The only negative change is that mounting is slightly more difficult,
although my mounting seems to depend on the number of observers more
than anything else.

There are two positive changes for me. The first is that shorter cranks
make it easier to ride while I am tired. The second is that I am
significantly less saddle-sore after long rides. In both cases, I
believe that the narrower range of motion compensates for the extra
effort required.

There was one change that I didn't notice. Specifically, the transition
to shorter cranks didn't seem to affect my speed in any noticeable
way.

One other thought - I weigh a bit more than the average unicyclist, and
that extra leverage might make it easier to handle the heavy coker
wheel.


--
wentz - Heh, Albatross is sorta blah, eh?

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I've tried 125s, 150s and 170s on a Coker. I prefer the longer cranks.
I find that I can usually go just as fast on the longer cranks.
Occasionally when spinning on gentle downhills I wish for shorter cranks
but for the most part I'm satisfied with my current crank length.

I've always figured that my preference for longer cranks was due to a
lack of skill on my part. The shorter cranks required more mental (and
perhaps physical) energy from me.

With the longer cranks I can spin up to my maximum without worrying
about a lack of control.

Unfortunately I don't have any objective metrics to quantify the
differences.

I think it is clear, however, that given a sufficiently skilled rider
the shorter cranks will usually be faster on the flat.

-mg


--
mgrant - Ever hoping for the best!

The sun is the same in a relative way but you're older, shorter of
breath, and one day closer to death.
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I'm running 150's on both my 24x3 Muni and my Coker. The 28'r wheelset
has been sitting idle for quite some time as I have stuck a 24" wheel in
it's frame to use as a loaner. Now that I've built another Muni frame,
I'll slap the 28" wheel back in the frame this weekend and try riding it
with 170's and give you my opinion. I was running 140's on the 28'r and
found it to be a little too twitchy. That was the main reason that it
was put into retirement.


--
Krashin'Kenny - Crash Tested

If you ain't crashing, you ain't going fast enough!!!!!!!!!!!

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I used 114mm cranks on my 29er, but as you have described, I didn't
really feel 100% confident on the roads. Stopping securely was a big
problem for me as I couldn't just jam the back foot on as the wheel kept
going!

I loved the unicycle and it was great going on hard surfaces and even
light trails for that matter, but I just didn't use it much and took the
muni across the park.

I'm getting a new Dave Stockton built 29er soon that has 150s for trails
and light muni and also a brake. This should take my favourite elements
of the road 29er with a couple XC/muni characteristics thrown in.

If I really miss the road aspects, I may get a spare wheel with 125s and
a Big Apple built up.


--
one wheeled stallion - Guerilla Unicyclist

OWS

"I'm going to be polite in this whole message except for here.

Idiot." - John Foss


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I think unless you live somewhere really hilly, 125s are the maximum
worth putting on a 29er. Anything more and it's just a bad version of a
26" or a 24" muni. You can ride a lot of cross country mountain bike
trails and most normal hills with 125s. If I was only road riding, I'd
probably have 110s.

Obviously Sheffield is very hilly though, so you might have a point
about the longer cranks.

On the coker, I never changed the cranks from 150s, because I didn't
want to make it into a just road riding machine. I'd not consider going
longer though.

The big trick to short cranks is to ride them daily for a few months,
just make yourself ride it to work or whatever every day.

Joe


--
joemarshall - dumb blonde
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I have two 29'ers - one intended for the road fitted with 140's and the
other intended for off-road fitted with 170's.

I mostly ride off-road using the one with long cranks. If I was into
road riding I might go shorter than 140 but right now they both suit me
fine.

SH


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For "Lo!" sayeth the Prophet, "It is written that wherever two
unicyclists gathereth, they shall speak of cranks, even as two
bicyclists shall speak each unto the other of gear ratios, and neither
shall agree..." (The Book of Cokeronomy, XIII.666)

Funny this. I used to be a short crank fetishist, and got down to 89s
on my 24, and tried 102s on my 28. On my Coker, I have flirted with
125s, but returned to 150s; on my 28, I have flirted with 102s and 125s,
but I'm happiest at 110 - but that's a pretty light wheel, and is
strictly for road use, except when I go off road with it.

This is my theory:

You must look upon the rider and cranks as an engine. Just as a
motorbike engine has a bore and a stroke, an optimal rev. range, and a
power curve, so does the unicycle.

The "stroke" works just the same way on a uni as in an engine. Long
stroke = more torque, but restricts revs. Short stroke allows higher
revs, but reduces torque.

But in an engine, the maximum rpm is influenced by the speed of
combustion of the fuel. Adjustments have to be made to the timing (when
the spark fires) as well as the shape of the combustion chamber and the
position of the spark. Put very simply, if an engine is over revved, it
can become less efficient because the combustion isn't being used
optimally, and for a number of other reasons such as "valve float"
etc.

Now, on the unicyclist, the "combustion" or "firing" is the action of
the leg muscles. Are you a sprinter or a plodder? What is your optimal
stroke and rpm for your particular leg muscles? If you have long legs,
you might need a longer stroke to use the muscles more effectively; if
you have heavy legs, a shorter stroke might make pedalling smoother and
more efficient. And so on.

So, simply changing the length of the crank does a lot more than
changing the leverage you can exert, and the maximum rpm that you can
achieve or maintain. Do the thought experiment: How fast could you
pedal with 5 mm cranks? How fast could you pedal with 500 mm cranks?
At these ridiculous extremes, it is obvious that simple arithmetic won't
give a direct comparison of possible speeds - so why should we assume a
straight line graph for comparing conventional cranks?

The Constant Footspeed Hypothesis which many of us have used as a tool
for analysing the effects of changing crank lengths is not even a
tenable hypothesis any more. It is simply a rule of thumb useful for
gauging the likely effect of a single step change of crank length (125s
to 150s, or 150s to 170s, for example).

And none of this takes into account the confidence factor, and the
control, or safety. Also, although the relative dimensions of the
cranks and the wheel are important, the absolute sizes matter too. For
example, it is reasonable to guess that a 20 with 5 inch cranks will
perform similarly to a 24 with 6 inch cranks (the ratios are identical),
but it is not reasonable to guess that a Coker with 9 inch cranks, or a
4 inch wheel with 1 inch cranks would perform similarly - although the
ratios would be identical.

I found 170s totally unuseable on my 26. I could imagine having more
success on my Coker - and here's another comparison with a piston
engine: long stroke engines tend to have heavier flywheels.

I'm with Dave on this one: safety is the primary concern when riding on
the road. Longer cranks are safer, although the definition of "long"
varies from rider to rider (as the actress famously remarked to the
Bishop).

And on hills, long cranks are easier. Short cranks tend to work better
on smaller wheels - but not on a simple ratio basis. I love my 28 on
110s (30%) and I love the Coker on 150s (33%). Only a 3% difference?
No, 3 percentage points. Think about it, the Coker has 10% more
leverage (33/30). That's significant.

But you can superficially appear to support any argument with selected
statistics. It's all about riding, and for riding, selection of crank
length is about preference and experience, guided by rules of thumb.


--
Mikefule - Roland Hope School of Unicycling

Everyone should be fatuous for 15 minutes.
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I find my 29er to be very twitchy (ie little flywheel effect) with 125mm
cranks. I'd only ride it with such short cranks on the road. For
offroading 140s or 150s are way nicer. I agree with OneWheelDave that
the 29er/150 combination makes a very good XC/singletrack uni.

To me a 29er with 170s is a bit of a joke - you lose all the 29er's
speed potential and use heaps of energy thrashing your legs around in a
big pedalling circle, not getting anywhere fast. I've tried this and
hated it!

I've ridden my Coker with 125s, 140s and 170s. 125s are nice'n'fast on
the road but make my knees suffer, so 140s are a better all-round road
crank for me. For offroad Cokering 170s are nice, and I'd consider 150s,
but haven't tried this length yet.

One Wheel Dave - I think you'd be surprised what can be ridden on a
Coker. Enormously steep hills have been ridden up and down on Cokers.
Especially if you have a selection of cranks to experiment with, you
won't regret getting a coker.

As for your poll, it depends on the type of riding you're doing (on- or
off-road). But in general I like longer cranks for offroad, and shorter
for road riding.


That's my 2c on 29er and coker cranks!

+()|\|y


--
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