G24, Schlumpf help + Ratio Chart (help)

I’ve used this chart to plan cranks sizes for my 29" and 24", and found it to be generally pretty accurate for my riding circumstances.

I have 2 questions, I have a G29 that will be ridden next year for uni packing trips but if I don’t like speed I was thinking of converting it to a g24 and using that for unipacking and pack rafting.

To those who ride a G29, how accurate is the chart?

For those who have experience with a G24, how is it riding?

Also how hard is a Schlumpf to ride? Ive been reading a lot of threads and it seems like it takes quite a bit of effort in high gear.

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I have an early schlumpf 29er and I find the chart is accurate for my round town riding style. Not any much harder in high gear and nice for comfort cruising a paved path. I’m useing 150’s

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I like the chart, but it is not quite so accurate in my opinion for the geared wheels.

It seems like when the Schlumpf hub first appeared, the gear ratio was assumed to be 1.5 to 1 and so people were saying “it can make a 24 ride like a 36”.

But there are a few details which make that simple arithmetic wrong in practice:

The Schlumpf hub ratio is NOT 1.5, but actually is 17/11 = 1.5454…
This ratio has been confirmed by Florian.
(sun + ring) / ring = (36 + 66) / 66 = 17 / 11

Also the 24 muni tire size is usually 3.0 but the 36 tire size is usually only 2.25

The rolling diameter of a tire can APPROXIMATELY be calculated by taking the ETRTO rim size in mm and adding 2 times 25.4 times tire width (nominal inches) times 1.05.
[the 1.05 is a bit of a fudge factor to get the typical height from nominal width].

The rim ETRTO value for a 24 is 507mm and for a 36 it is 787mm.

So a 24 x 3.0 tire has a rolling diameter of 667mm approximately.
And geared 24 x 3.0 has an equivalent rolling diameter of 1031mm approximately.
But a 36 x 2.25 tire has a rolling diameter of 907mm approximately.

OK, all very boring arithmetic, but the bottom line is (ta dah!):

A g24 with a 3.0 tire could be slightly more than 13% FASTER than a 36 with a 2.25 tire.

Yes, that is merely faster IN THEORY. My guess is that most would be actually faster on the standard 36 than the g24.

And of course, the chosen crank size is affected by leg dimensions, leg strength, desired speed, comfortable cadence (so very much a personal choice).

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I need to first say: I’m by no means a talented schlumpf rider. But I have recent experience of learning.

I am also building a G24 alongside a G29… so I can relate to the decision making here. (Kinda, as getting both )

First off: as for a Schlumpf being harder. Yes I think they are, initially - but with practice I believe they become more normal.

I’m in the stage where I still get more of a workout from riding my G26 verses my normal 29er… that’s probably due to partly the muscles I’ve yet to train up for the new wiring needed for geared riding - but also the sheer mental focus. As I feel you do need to rework your mental picture of what unicycle riding is.

Now: purpose - for me I unicycle as I get a buzz from it. It’s pleasure at the end of the day. Be that from the zoned in focus, physical effects of the exercise, or doing something that feels kind of impossible - a challenge overcome.

Geared riding for me is just: ONE MASSIVE TRIPPY EXPERIENCE. When it clicked for me, I was on a super high. Not just high gear but some kind of euphoria.

There’s nothing really practical about geared riding, but perhaps it makes unicycling feel a tad more “advanced” or versatile than fixed riding. I don’t really know or care.

There’s clearly those who take any discipline to the next level - and go UniTouring with a geared wheel. It’s amazing. Maybe one day I might consider it - but I’d probably prefer the simplicity of a fixed wheel if going for hundreds of miles.

I expect that when taking wheels on a plane is limited to events - taking a geared 29er could be the best of all worlds, but it would be for a specific event where I have trained up to take part in. So in some ways you do need to find projects or events to use a geared wheel - but I’m thinking it might start making me go to events more and purposefully train to take part competently.

(I’m conscious of writing tons - and that this coming from someone with admittedly limited geared skill, might smack of hubris, so I’ll wind down)

Regarding the the 24” wheel - I expect it to be more twitchy and require more focus than a bigger wheel geared up.

It’s been said before. This is primarily I believe why G36ers are popular. Yes they can be used for going crazy fast, but also for going moderately fast with a nice cadence.

I suspect due to the twitchiness of a G24 ride I won’t be going that fast. But I will be more mentally able to ride in more crowded spaces I feel.

My hope is I can pack this up for trips to mainland Europe. Plane, Train, Bus - all feel way more doable, and I can even get a rucksack if I so wish to carry it.

I like the idea (and I say idea as I have no clue if it’ll prove true) of being able to ride around a city somewhere - paths etc and when it opens up have a bit more scope to cruise along faster, with a nice bike-like cadence.

People please correct me if I am wrong here but my understanding and perhaps a lesser commented on aspect of riding in high gear is the increased wheel turning leverage you get. The balance envelope is (I think) a lot smaller, but also your power to drive the wheel forward is amplified by the gearing. This means that while a 24” wheel is going to be twitchy and need a lot of focus over bumps, the power to get over them is there under your feet.

The leverage is also forwards and backwards - which took me a while to trust and feel, but this means that braking (with your legs - back pedal pressure) is also increased.

My taste of riding my old G36 - the initial sensation was the wheel was very “weighty”. I don’t actually mean heavy, but the power you need to turn it at first felt almost impossible. All while trying to keep balance (L/R) in point.

When G26er riding clicked I recognised I was putting my centre of gravity in what felt way more over the front of the wheel than on my fixed wheels - so much so it almost feels like you’re doubly trying to fall. On tiptoes wanting to hit the ground. All of this is re-wiring the brain’s approach to unicycling and when you feel it click it’s a boost.

I will draw this long deep personal dive into my views and feelings on this topic to a close. Hope it helps and doesn’t re-tread old ground.

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Yes while as an engineer I agree with gocup because he is factually right. Mindbalance has documented the details of riding a higher “geared” hub. Since I own and ride uni’s from 16" to 36" wheel size and everything in between my personal feeling is that the chart is a basic description to guide you to setting up your hub and wheel with crank size to what you can expect. Gocup brings out the fact that it ignores the differing tires on rim diameters. This even on a non geared hub makes a big difference. So you would definately notice this on your guni or fat tire uni. Use the chart to set up for personalizing your set up for maximum enjoyment of your riding. My G29 is stone stock schlumpf as it was delivered to me years ago frame, tire size and all. chart is pretty accurate for that but as you change factors like tire size, pressure and crank length it will differ. Thanks guys, a great discussion.

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Oh yes, at one early point I made my own 24x3.5 Muni with 180mm primo cranks for local trails that had hills. I love the charted comment on this set up, and the answer is yes.

The Chart is interesting, though the best crank length depends also on the ability and fitness of the rider. The pros ride shorter cranks;-)
I like shorter cranks for the downhills, my knees need longer cranks for the uphills. So with my G 29 I ride the 137 spirit, with other munis shorter cranks.
The Schlumpf hub ist fantastic, if you have experience with different wheel and crank sizes, it is easy to get comfortable. If not it needs some practice:-)
In my opinion the schlumpf hub fits better in 29 than in 24, I suppose because the weight does not matter so much. I like it much more in the 29er.

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I don’t like this chart.

It makes you think that all you have to do is change the cranks of a 20" to ride at the speed of a 36", which makes no sense.

It makes you think that a G24 is equivalent to a 36". Sure, the legs turn at a similar speed, but the ride is very different.

As far as speed is concerned, for the same ratio, the bigger wheel is always more interesting. The wheel is more stable and has better clearance.

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As far as speed is concerned… bigger wheel has pros and cons.
Have you tested a g24? Have you tested the flywheel effect of a hunirex with fat tire? Have you tested the flywheel of a light 36" versus a g24?
They are different and every choice has it’s reasons. Lots of people consider Hunirex a cheapo uni. It is a great machine. Lots of people consider their uni the best, but they never tested others… I don’t think bigger is better for speed always

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For me, the disadvantages of big wheels are the size, the weight and the jumps.

I regularly use all kinds of unicycles (UW, lunicycle, freewheel…).

Although I have been injured on a pedal strike, I find the hunirex to be a very interesting geared unicycle. I’m convinced that it would be better with a 29" wheel than a 26" wheel.

I have never ridden a G24, but I have ridden G26 a lot. I find that it only has weak points compared to a 36" light. The 36" is much more stable in all conditions due to better clearance. The inertia of the wheel also offers a lot of comfort. In 36" there is a lot of tolerance on the front-back position of the core above the center of gravity.

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Bigger wheels are not necessarily heavier than geared smaller wheels. My Oracle 36 is actually lighter than my schlumpf KH26. The hub itself weighs a ton.

The Hunirex is also a very heavy beast.

Right… But false
The wheel weight can effectively be quite similar. But the rotational weight - what is really interesting for road riding - is (almost) always bigger for a bigger wheel, due to the distance between the hub and the tire.

Not really but I see your point - the rotational mass is, again, not necessarilly greater on a bigger wheel; but big wheels tend to have more angular moment, which is proportional to the rotational mass, and the square of the radius, where the latter is a much greater factor. The angular moment is actually what determines whether a wheel feels heavier or lighter.

Just to clarify: I’m not an mechanical engineer and English is not my native language. But, as far as I remember my physics class, “weight” and “mass” have a different meaning - at least in French. As I understand it, the rotational weight takes into account the radius, as you stated. But I may have used the wrong words
Feel free to correct me if I’m wrong, I’d be happy to learn the English words on that topic!

I agree larger wheels do normally have a larger angular momentum and for some uses that resulting flywheel and gyroscopic effect makes the larger wheel more manageable.

However the angular momentum is the mass x radius x velocity ( L = M x R x V). Note that the radius is not squared.

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That chart however is not related to speed.