Big Wheels, Long Cranks...

Unicycles and Equipment
1

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://www.unicyclist.com/forums/showthread.php?s=&threadid=34009&pagenumber=1

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?

2

The poll I posted hasn’t surfaced :frowning:

So I’ll ask it here: -

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).

3

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.

4

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

5

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.

6

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.

7

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

8

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

9

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.

10

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

11

Update 1.

Several days of 29-er with 150’s have passed and I’m still feeling that this is the ideal combination for the area of Sheffield I’m in.

Though on a couple of occasions I’ve had a mild hankering for some of the characteristics I remember of the 125’s, it’s more than made up for by the fact that I feel much more in control.

It’s amazing how fast the 29-er goes with 150’s especially on steep stuff and rough ground. I think that this is due to a combination of being happy to be at max speed as the extra length of cranks provide a ‘safety net’, and also the phenomenon I’ve mentioned before of the contrast between ‘acual speed’ and ‘illusory speed’.

ie as someone who lacks a cycle computer I find it difficult to judge actual speed, but often I’ve found that spinning fast on a muni gives an impression of greater speed than the ‘actual’ higher speed of a big wheel combination.

Anyway, the 29-er with 150 cranks seems to provide a little extra of both actual and illusory speed! and the extra leverage/control gives a nice feeling of security if anything goes wrong.

The rides have been very high energy, with access to the monster road hills that previously were only feasable on the muni, I’ve found myself climbing like a maniac and arriving home never less than fully drenched in sweat :slight_smile:

Interestingly, even the steepest of the uphills seem easier than on the muni, the bigger wheeler and slightly higher gear meaning that progress up them is faster.

Though the downhills are all very do-able, I’m feeling that 29/150 is stressing the joints more than the muni would.

Off road, things got even better, the trail that I often ride muni on was gone in a flash on the 29-er.

None of the inclines, declines, rough spots or small drops were any trouble at all- almost as smooth as on the muni, but much faster. Having said that, I can feel the wheel flex on some small drops, but I’m sure that that’s partly due to my rim being the stock Nimbus 700c of two years ago.

I’m inclined to say that the 29-er with 150’s is surely a prime contender for the title of- ‘ultimate speed orientated XC muni’ machine.

Next week I’m going to be spending several days in Milton Keynes with my brother and his family; I’ll be taking the 29-er and looking forward to some distance rides on the much flatter terrain, I’ll be taking a set of 125’s and it’ll be intersting to see if I switch over to them.

12

Well, I use the 150s that came stock on my 28. I wanted to switch to 125s, but UDC was out of stock on ALL of them when I called (except the expensive ones.)
So, I’m still using 150s.
My vitural 60" Guni will have 175s or 170s, whichever I can get cheaper.

13

Well, here we are a year or so on, and my Coker remains on 150s, but my 28 is down from 110s to 102s. My MUni remains on 150s.

I think it’s as much to do with leg length as crank length. I find difficulty pedalling smoothly and fast on 150s, but the flywheel effect of the Coker wheel helps to smooth my action. With the 28, the short cranks are there because I like the feel, rather than because I think they add significantly to the speed.

Of course, my riding is mainly on the flood plains. Rob and I did over 1000 feet of climbing on Dartmoor and I was grateful for the 150s then! Dave, your place in Sheffield has some exceptionally steep hills, so I can see why you prefer the longer cranks. I would, too!

14

From reading all of this it sounds like the best crank length is a combination of three main factors:

  1. Steepness/roughness of terrain

  2. Rider body size and preference (some of us like to pedal faster than others)

  3. Purpose of the ride (casual, workout, A to B, or race?)

My Coker has 125s on it. I’m sure I could get used to shorter cranks, but only for pretty flat riding. There are some hills on my commute, but none are steep and the 125s are fine. Sometimes I worry on the way down the hills (I let it roll out), but otherwise it’s fine. I have also used 160s and 170s for MUni. Which length is “better” for trails has a lot to do with the difficulty/steepness of those trails.

My 29er is normally ridden on road with 102s. I feel I have “enough” control on that crank size, though it’s a bit of a compromise. Anything longer and I will mostly wonder why I’m not on my Coker.

With 160s on it, I love the way it rides on trails. Just don’t bring it to Downieville! That ride requires a robust wheel and either longer cranks or a brake.

My riding background includes racing, which means lots of riding at very high RPMs. So I generally like my cranks shorter than the average rider.

Currently I have 140s on the 29er. I put them on for the cross country race at NAUCC. Due to the mostly flat and not technical nature of the race course, the 29" wheel blew away the competition. That’s a good crank length for easy trails.

With those cranks still on, I rode the 29er to my wife’s office the other night, to pick up her car. This was a road ride, mostly on side streets. The cranks definitely felt too long, and I could tell I was wasting a lot of energy making the bigger circles with my feet. I was pretty sweatty by the time I got to the car. I definitely like something shorter for a flat road ride on the 29er.

15

Wouldn’t it be nice if you could buy a crank system where you can vary the length of the cranks with simply the turn of a screw?

With all the talk about experimenting with different crank lengths and doing the same myself I may just design something.

Look for future posts on the subject.

Happy crank changing!

16

Check out this thread for lots of ideas concerning adjustable cranks-

http://www.unicyclist.com/forums/showthread.php?s=&threadid=30079

17

oops…I meant to post in the other thread, not bump this year-old one.