Thanks for infos. Yes, I still ride this uni with 145mm qu-ax cranks and I wanna buy Nimbus Muni 26" with some 150mm cranks.
So if you like the feel you get with your current uni, then you should be able upgrade the Nimbus to Moments or Spirits and you’ll be fine.
Just to double check, take a measurement across the wheel from one outside pedal thread to the other outside pedal, then tonight I can measure my Nimbus Muni and KH and let you know how they compare.
Granted. I will revise my quote to say that many track racers prefer narrow setups, track-specific unicycles are built to be narrow, and many of the top fastest riders ride narrow. But like everything else, that doesn’t mean it works for everybody.
Well-designed versions of both crank and hub-mount systems work. It depends on your balance of priorities. Neither system is a merely a retrofit, and both have issues that require resolving (by good materials and design). While all good unicycles take from bike technology, I would never use “because it’s used on a bike” as justification for (or against) applying a bike related design on a unicycle. There’s a lot more to it than that.
Hub-mount disk systems are familiar technology in the bike world and they place the disk furthest away from the foot. It is easy and clean to install, and looks good. On the negative side, the rotor mount requires a dished wheel and narrower flange spacing that is geometrically weaker for a given hub width. Whether this a problem or not will depend on the rider, the wheel size, and the strength of the rim. In many cases this will not be an issue and I expect the hub-mount approach to be popular just as it is on bikes.
For crank-mount systems I’ll comment on the Spirit setup specifically, and why I chose to go this route:
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Strength-weight ratio. Many riders push the limits of wheel strength, even (or perhaps especially) beginner-intermediate muni riders. This is true for both catastrophic wheel failure and long-term durability. At the same time, weight matters, especially rotational weight in a wheelset. If I added a disk brake system to KH unicycles, I did not want to accept either a compromise in either geometric wheel strength or increased weight. This is particularly the case given that rim brakes do work - braking performance shouldn’t come at the expense of riding performance. Spirit cranks allow installation of a disk brake while maintaining the same symmetrical wheel build and wide flange spacing as a standard non-disk hub: in other words, a strong and durable wheel geometry. The crank rotor mount is also very slightly lighter weight than a hub mount (adds just 2 grams to the right crank), although you would never notice a difference in practice.
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Compatibility. While I’m personally in favor of using a brake, many (actually most) riders choose not to. I also wanted a system both compatible with disk brakes and 100% functional without them.
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Versatility. From a design perspective, it’s helpful if the exact same system can work from 24" to 36", with a single, standard 100 mm hub that works across the entire line (from 20" to 36").
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Q-factor. Debates on the “best” Q-factor will go on forever. While too wide is undesirable, I do think that “narrow as possible” is too extreme and simplistic. Thousands of riders in the past 7 years, including myself, have found the Q-factor on original Moment cranks with a standard 100 mm hub to be a good balance of priorities: pedaling stance & knee comfort, saddle comfort, avoidance of pedal strikes, and just enough outwards flare to avoid ankle bashing, heel clipping, or accidental shifting on a geared hub. As such I wanted to keep this similar on Spirit cranks.
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Easy install. With high-end materials (7050 Al cranks) and a spacer between the crank and bearing, Spirit cranks consistently mount at the same position on a standard ISIS hub. This is a requirement for the crank-mount system that must be resolved by good design. Unlike the standard Moment hub, some (resolvable) fit issues do exist with the close tolerances of the geared hub. However, these are issues associated with the geared hub design (that can and will eventually be resolved), not the Spirit cranks or crank-mount setup.
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Compatibility with the geared hub. The Spirit cranks are the only compatible disk brake setup with a geared hub. For a variety of reasons, the KH/Schlumpf hub design benefits from using the full width of hub for the gearing, so this is unlikely to change in the foreseeable future.
The potential negative of the disk-mount setup is that it appears to place the rotor in a more vulnerable position for clipping the rotor with your foot or ankle while riding. After more than 1.5 years of testing on all kinds of terrain, I have yet to hit the rotor with my foot. I can’t even do it if I try to do it. Personally I have not heard reports from anyone else having this issue, either. I’m sure that someone, somewhere, will manage to do this sometime, but generally it appears to be a non-issue. Of course, all bets are off for wipeouts, for either hub or crank-mount systems: getting caught up in a unicycle while wiping out can get you tangled in ways that you’d never otherwise foresee.
In terms of inadvertently bashing the rotor on the ground, I don’t think either the hub or crank-mount system is more or less vulnerable, and in both cases it is probably less vulnerable in practice than it appears to be when you look at it. I have tossed my disk brake unicycle hundreds of times now, without damaging the rotor.
I will say that the Spirit cranks were a challenging design project, so I’m pretty relieved that they work well.
Kris
Hey John, I’m just razzing you 
I’m glad there are choices, it makes it more fun for gear whores like moi 
So Kris, any chance we’ll get a narrower waisted seat or something with a different snout? I’d be curious to know if you have been working on a new seat design that would help redistribute the weight so there’s less “taint” pressure and rubbing. I do like the Freeride, but a more comfirtable seat, mmm, that would be worth money.
At the moment, my preference is to have a single frame and adjust the foam shape (e.g. Slim, Street, Freeride) to consider a spectrum of rider preferences, plus offer the T-bar to re-distribute weight further back. Not everyone wants a narrower waisted saddle, either, so I have to come up with something that hits the “sweet spot” in terms of what works for most people most of the time.
Injection molds are expensive considering the number of saddles that can be sold in a year - more than US$40,000 all told (mold tooling + design drafting, but not my time) went into development of the Fusion saddle frame and bumpers. Of course, having multiple molds would be great but all told I’ve been pretty happy with how it turned out - certainly an improvement over the previous saddle frame.
Interesting. I’ve got 125 QuAx cranks on my road 29er (Ventures on the muni and 19er). I have to admit I’ve not noticed the difference in terms of knee comfort or anything else like that - in fact I’d not have realised at all if you hadn’t mentioned it. Shall have to get a ruler out and measure what the difference is. Though now I think about it, I do actually have less issues with saddle comfort on the 29er, which given one of the reasons for discomfort on the muni is the saddle feeling too wide and putting pressure on the inside of my thighs, I have to wonder if a wider stance might help with that. Then again the difference is at least as likely to be due to the shorter cranks.
I think I had been veering towards putting on a disk brake using Spirit cranks anyway - Kris’s comments above pretty much confirms to me that there’s unlikely to be any significant downsides (I’m used to wrenching disk brakes on a bike, so not expecting to have the spacing issues some are having). That does also give me the option of only having to buy a D-Brake and the cranks to make the upgrade on my current muni, as I even have a spare brake I could use for now.
Given I also often catch my right ankle on my 19er (I have a very enlarged ankle bone due to a chronic ankle injury) maybe I should also bit the bullet and get some different cranks for that…
Here’s my Nimbus Oracle Ride review.
(I know, it’s also in my sig, haha)
So after riding some muni on someone’s KH29 the other day, I decided to get the KH29. I don’t want to wait until November, and I am a bit hesitant to get the first iteration of a uni design.
I am going to get the crank-mounted discs.
The KH29 I rode on was a bit high for me. My seat post was a bit long and I couldn’t get it low enough for me. Probably only 1/2 inch too high, but enough to be noticeable. I was on trails that were mostly rolling, but with some rooted and rocky steep uphills. Nothing super technical. I did pretty well. Though I had trouble on the steep sections keeping my wheel moving. Mind you, I have never ridden anything bigger than a 26 before.
I was on 150mm cranks. I am 5’7" and am now trying to decide between the dual-hole 165s vs the standard dual hole 150s. the guys I rode with said they sometimes have trouble with the 165s being that it hinders their rolling up the hills, but Josh from UDC recommends 165s. I know it comes to preference, but I have not ridden with both, so I don’t know which to get, and the Spirit cranks are expensive. Advice please…
If you’re planning to ride mostly road, with some xc/light muni, go with the shorter cranks. If you’ll ride mostly trails and want to push into harder trails, go with the longer ones.
Personally I now only use my 29er on trails, and use 165’s. But 125 was good for riding the 29er on road and paved bike paths.
Edit: I note I’m 6’4" so maybe that affects my preference, but the leverage factor is the same regardless of the length of your legs. 165 is still shorter than most bike cranks.
Mostly commuting on the street, with muni on some challenging trails a couple times a month.
So really both types of riding. I can’t afford two sets of cranks, and prefer the dual hole.
The choices are:
127/150
or
137/165
If I get the 150s, I would ride most of the time on the 127s and use 150 for muni. I’ve heard that if you are shorter (I am 5’7"), the shorter cranks may actually be better.
With the commuting, the shorter cranks are probably better for you. If you’ll be switching holes that often, you might also consider a quick release seat clamp.
150’s on trails are fine, and preferred by many over longer cranks.
Ultimately you’ll end up with a 36er for your commute. 
Oh god more choices. If you had to choose 3 unis what size would you get for trials muni and commuting? 19, 26 36? Would a 29 be in the mix?
Trials is easy, 19. That’s the point it stops being easy - I currently have a 26er for muni, but very tempted to try a 29er (I have a 29er for use on road, so it’s only a case of swapping the tyre, swapping the cranks and lowering the seat - don’t know why I haven’t done so already 
) Of course some people will suggest you actually want a 24er for muni - and doubtless that would be the preferable size on some trails. Then again some people ride muni on a 36er…
As for commuting, well most seem to prefer a 36er when they get good enough, but it does depend on your route - my standard transportation route from the village I live in into the local town is twisty and tight enough that I’m not sure I’d ever be happy riding a 36er on it. What I really want for that is a 29er guni!
Yes this is the point where a gunk looks good. I don’t want 4 unis. Then again the appeal of a uni is simplicity and a custom made geared hub is probably complex. What if it breaks etc.
The ones you end up riding are the ones you should keep.
I sold my Trials, it was never ridden all that much.
I sold my 24’s when I spent all my time on a 26".
I sold my 26" when I spent all my time on a 29".
I now split my time between 36, 29, 32, with an occassional foray on the Oregon 26 (soon to 29 x 3).
Some people keep all the unis they buy, other folks have a limited budget and have to buy one to sell one.
When I was still riding 26", I didn’t foresee myself going to a 29" because it was too big for muni, but now I ride a 29" a lot and I consider it small in contrast to my 36er.
A guni, well, that’s a totally different beast all together. Not for me, at least not right now, though the force is strong in this one. Gunis just don’t work in the same conceptual framework as a bicycle, so just becsuse we are all familiar with bike gearing, we assume we know unicycle gearing, but they are no more the same than veggie burgers and beef burgers. Gunis work, but not like you think. Try one before buying so you know what you are getting.
If I could only have three unis and I rode trials, I’d have a 19, 29, 36. If I rode trail trial and muni I’d have a 24, 29, 36. If I only rode street I’d have a 29 guni and a 36, maybe a 36 guni.
good choice. I love mine! Lighter than my 26" Oracle and rides like my 36er except manageable off road.
get the 165/137 cranks. I love mine! 137 is plenty short for the road and you will appreciate the leverage of 165 off road. Then, when you get a 36er (the only real road uni), you can go super short on cranks.
For such a simple sport, the buying choices for uni are awfully complicated!
Yep I was amazed how light it is for such a beast. I was
Able to hop steps with out too much of a problem. I am used to my trials so I could feel the rim flex which is weird. Forgot to mention that is enjoy idling and hopping at lights so probably the 29 is the way to go for my commute.
Why are 150s standard on the kh29 as opposed to the 165s?
Because Kris is a far more talented rider than you and I. He does make a good point that shorter cranks minimizes the dead spot when rolling rocks and roots riding MUni but I would listen to Josh’s advice. He specs unicycles for the common man. Kris specs them for his own preferences. Not that there is anything wrong with that. If you’ve got mad skills, shorter cranks are the way to go. Ben King can climb bumpy hills on his KH29 (150mm Moments) that I could not get half way up on my 26" Oracle with 165 Spirits. Like you, I saw that KHU specs the KH29 with 150mm cranks so that is what I got. It was not long (I gave them a fair shake on 3 different trail rides) before I put them up for sale on the trading post and ordered myself a set of 165’s. It was a costly mistake that I’d just as soon see you not repeat. Of course it all comes down to personal preference but if you are just getting into MUni, I’d start with the longest cranks I could get my hands on.