As there are so many people trying to ask what sort of unicycle they should buy. I decided to narrow it down a little and write a bit of a review. Here is what I’ve done and hopefully tomorrow I’ll attach it as a word document.
Mountain Unicycle Buyers Guide
When picking out a new mountain unicycle it can be very intimidating with so many options and fancy names. In this, I will go over all the separate parts in the mountain unicycle (muni) and try to break it down so that it is easy for you to decide what you want. To clear things up, just because a unicycle has a knobby tire, it does not mean that it is a mountain unicycle. Many unicycles are not built to withstand to extreme forces put on them by mountain unicycling, which makes them considerably cheaper than unicycles built specifically for the trails.
Overview
Frames: In general, unicycle frames are made out of either aluminum or steel. Steel being the cheaper of the two. Other materials such as carbon fibre and titanium do exist but they are much more hard to find and are very expensive. Here, I will only go over aluminum and steel frames.
Crown: The crown is the part of the frame where the two fork blades meet and attach to the seat post tube. There are three kinds of crown on mountain unicycles: round, square or flat and rounded square. Round crown is great for muni as it is out of the way therefor minimizing painful knee strikes on the frame. Square or flat crown is more common and enables the rider to put their feet on the frame, which isn’t very necessary in muni. Rounded square crown combines the best of both types of crown by avoiding knee strikes yet enabling the rider to put their feet on the crown
Steel Frames:
• Most steel unicycle frames require a seat post diameter of 25.4 mm. Occasionally you will find a unicycle with a 22.2 mm seat post but usually both the frame and the seat post are weaker hence the smaller diameter.
• Compared to aluminum frames, steel frames are half to two thirds cheaper. They are also considerably heavier than most aluminum frames.
• Steel is quite flexible so it is not uncommon to have the tire rub on the frame when you are putting a lot of sideways force on the frame. Such as when you are climbing or turning. Certain frames will almost feel “sloppy” on a steep uphill. A “V” frame creates less flex but also adds more weight. That being said, if you don’t ride super aggressively, and are a smaller rider, the flex will be minimalized.
• Lastly, steel frames are bomb proof! It is almost unheard of one breaking. They can be bent when hit hard but can usually be straitened without too much hassle.
Aluminum Frames:
• Other than Nimbus and Qu-Ax, all aluminum frames require a seat post diameter of 27.2 mm.
• Aluminum frames are very light therefor lessening the overall weight of the unicycle, which makes for a more agile ride. Going from steel to aluminum, there is a large jump in price so be sure that you really want it and are willing to spend the extra hundred dollars.
• Aluminum is quite stiff so there is next to no tire rub and the frame will feel very solid. The average muni rider will never get tire rub on an aluminum frame.
• Because aluminum is so stiff, the frames do sometimes break but it is still very uncommon for one to break and even less so with muni. The chances of a frame breaking are so small that you shouldn’t even have to consider it when deciding what frame to buy.
Hubs: When picking a muni hub, there is really only one major thing to worry about: a splined axle. In the world of unicycling almost all splined hubs are ISIS (International Splined Interface Standard), this means that you can inter change crank and hub brands and everything will still fit. The more expensive a hub is, you are paying for it to be either lighter or stronger, or both. These days all ISIS hubs are quite strong so you don’t have to be choosy.
Rims: When it comes to muni rims, double walled rims are by far the best. Having a double walled rim adds a substantial amount of strength yet doesn’t add a large degree of weight. Single walled rims are slightly lighter but the loss in strength is far greater than the loss in weight. Single walled rims can be bent out of true or develop flat spots from just riding over roots or hopping off a curb. Another option when it comes to rims is getting a drilled rim. Drilled rims have a hole between each spoke to cut down on weight. Surprisingly, these holes do not compromise the strength of the rim. Looking at drilled rims, you may wonder why you have to pay more for a rim with less material (drilled) than a rim with more material. Generally the drilled rims are of higher quality so that is why they are more expensive. If a rim is double walled, it will be able to withstand the forces of a great deal of muni riding.
Cranks: Since it is essential to have an ISIS hub, it is also essential to have ISIS cranks. Be sure that both your cranks and hub are ISIS otherwise they will not fit together and you’ll have to buy either another hub or set of cranks which are both rather expensive parts. If you are buying a stock unicycle you obviously don’t have to worry about that. Cranks will either be tubular or solid, most muni cranks being solid. There are options to get cranks with two pedal holes so you can adjust the length of your cranks depending on the terrain. Most muni cranks range from 130 mm to 170 mm. Sorter ones giving you more speed but less leverage, they are ideal for light cross country and dirt roads. Longer ones are slower but have far more control and leverage. They are ideal for steep technical terrain and strenuous hill climbs.
Saddles: I wont get too in depth about saddles because it is mostly personal preference. Usually any saddle that comes with a mountain unicycle is of fairly good quality. After a while you will find parts of the saddle where you want more or less padding. I highly recommend customizing your saddle both because it is easy to do and helps a lot. These days, lots of people are making their saddles flat as it takes pressure off many unwanted places.
Tires: The selection of tires depends on the size of wheel you have. 26” and 29” having the most options mostly because that is the two most common bike tire sizes. Generally, the tire that comes with you muni is great for at least the first little while. Once you find your riding style, you will begin to search for a tire more specialized for what you ride. For example, if you only ride cross country, you’re not going to want a heavy downhill tire. Likewise, if you only ride downhill and freeride, you want a higher volume tire instead of a lightweight cross country tire. If you find you ride all sorts of muni, there are many different tires that work for all kinds of riding. Yet another, more expensive, option is to have multiple tires.
Seat posts and seat post clamps: Really, a seat post is a seat post, they are all pretty much the same. Some differ from others in weight but most are made of aluminum so the difference in weight between posts is relatively small. You just need to make sure that your seat post is the same diameter as your seat post tube. There are four kinds of seat post clamps for unicycles: quick release, double quick release, single bolt and double bolt. They all have their advantages and disadvantages. Quick release clamps are quicker and easier to adjust but they have lower clamping power. They also tend to get caught on things, which will open them and cause a wobbly seat. Double quick releases are relatively the same other than that there are two quick releases resulting in more clamping power. Single bolt clamps are smaller and have a higher clamping power. They are a little harder to adjust because you need a tool to do so. Double bolt clamps are just the bulked up version or a single bolt clamp. They have two bolts, which means they have the highest clamping power of all the clamps.
Brakes: A brake on a unicycle not only slows you down but also with a little practice makes your ride a whole lot easier. On a downhill, putting just a slight constant pressure on the brake lets you take most of your weight off the pedals so that instead of you doing all the work, the unicycle will just carry you along. On a brakeless unicycle, to slow down, you can only do so when your cranks are at the horizontal position, which takes away quit a bit of control. This means that without a brake, you can only actually brake two times in one revolution. With a brake you can brake for the whole revolution, which gives you a much smoother ride and enables you to ride much steeper terrain. There are three ways to mount a brake on a unicycle. The first and cheapest option is Hydraulic rim brakes. Pretty much every muni on the market these days have Magura hydraulic brake mounts so they are also the easiest brake to setup. The down side of hydraulic rim brakes is that when they get wet they loose a significant amount of their power. Disc brakes are fast becoming the new norm in mountain unicycling. They are barely affected by wet weather so you can ride in the rain without loosing your braking power. They also have much more power than hydraulic rim brakes and much better modulation. There are two mounting methods for disc brakes, external and internal. External discs are mounted onto the crank of the unicycle. This is a cheaper option but makes it a pain to switch cranks and leaves the disc more exposed to hitting roots, rocks, etc. An internal disc is mounted directly onto the hub leaving it on the inside of the frame and less exposed to damage, it also makes switching cranks no different from a brakeless unicycle. Generally, unicycles are only compatible with hydraulic disc brakes as they are smaller and will fit in small space available. It is possible to mount calliper and V brakes on a unicycle but unicycles are not made for them so it is a hassle to mount them and not really worth all the work.
Mountain Unicycles
24 inch mountain unicycles:
Nimbus 24” muni-$350: This is a sweet muni great for entry level riders up to veteran unicyclists. It includes all the things that make an off road unicycle worth getting; ISIS drive, double walled rim, a knobby tire and fairly long cranks. It also has Magura mounts for if you would like to add a rim brake. On top of all that, this unicycle is bomb proof so it will last you a long time. The one down side of this unicycle though, is that it is quite heavy. The extra weight wont be too noticeable at first, but as your riding progresses, you will feel a little sluggish and totally burnt out on the up hills. Over all, this unicycle has great value for what it costs, a little on the heavy side but still totally worth buying.
Nimbus Oracle-$620: Once again, nimbus has come out with an incredible unicycle for an incredible price. It was one of the first unicycles on the market to come fitted with a disc brake right out of the box. The extra bit of cash might be a turn off but for what the unicycle is, the price is off the wall. There is no other unicycle of such calibre available at even close to this price. The unicycle it’s self is very light and strong plus nimbus did not cheap out on the break. This unicycle is totally worth every penny and if you are looking to get a brake, this is the perfect unicycle for you.
KH 24-$690: A little on the pricy side but not over the top. This unicycle is extremely robust yet very light. Kris Holm Unicycles is leading the way in many aspects of unicycle technology and has been for many years. The passion behind the company really shows in the product. One of the best features of all the KH muni’s is that they come completely compatible for most disc brakes. They are one of the few brands that have a disc brake mount on the frame. The unicycle also comes with disc brake compatible cranks and a brake mount under the saddle. If you want to spend the extra bit of money and get a unicycle that is top of the line, look no further. The KH 24 is an awesome uni and it is super easy to add a brake when you are ready for one.
26 inch mountain unicycles:
Nimbus 26” muni-$360: This unicycle is exactly the same as the Nimbus 24” muni other than the bigger wheel. The larger wheel will give you more speed but takes away a little manoeuvrability. Most would argue that a 26” unicycle is the ideal wheel size for muni (keep in mind this is for grown adults and not children, they will most likely find the unicycle too big). One huge benefit of having a 26” is that you have an enormous selection of tires as most bicycles have 26” wheels. All 26” unicycles still give you great manoeuvrability while adding a little more speed, adding a whole new factor. This unicycle still gives you great bang for your buck.
Nimbus Oracle-$640: This unicycle is exactly the same as the 24” nimbus oracle except for the larger wheel. For only twenty dollars more than the smaller size, if you want a little more speed this unicycle is great for you.
KH 26-$695: Like all the other 26er’s, the KH 26 is no different from its smaller size. The unicycle is still super light and is disc brake compatible.
Nimbus Oregon-$850: This is a one of a kind unicycle, and not recommended for a first muni. Sporting a 3.7” wide tire, it is a beast when it comes to unicycles. It is also one of the few unicycles that come complete with a disc brake. The down side of this unicycle is mostly the added weight of the huge tire. Being so specialized, this unicycle most likely wont be the only muni you own. It also tends to wander of course on side sloped trails. This unicycle is best suited for advanced riders but can be a great muni to add to your quiver.
29 inch mountain unicycles:
Nimbus Drak-$360: This unicycle is quite similar to the 24” and 26” Nimbus mountain unicycles. It is a little heaver but not too bad (not many unicycles are). This unicycle also has a round crown frame, resulting in less knee strikes. 29 inch unicycles are best suited for cross country riding and mellow single track. That being said, with a bit of practice, you can ride the same terrain as most people could on a 24” unicycle. Like 26” unicycles, 29ers have a much larger tire selection than most other wheel sizes.
Nimbus Oracle-$720: After the huge success of the 24 and 26 inch Nimbus Oracle, Nimbus came out with the 29 and 36 inch Oracles. The only difference is the colour and the brake. The new brake is of slightly higher quality than that of the smaller Oracles. The 24” oracle is orange, the 26” is red, the 29” is blue and the 36” is green.
KH 29-$720: With the same specs as all the other KH unicycles, this unicycle will not disappoint. This unicycle is available in two different rim options. A wider freeride rim, and a skinnier cross country rim. The wider one allowing higher volume tires suitable for more technical terrain and the cross country rim takes off some unneeded weight as XC unicycling isn’t as hard on the equipment. Once again, the KH is an awesome uni and should not be looked down upon.
No big wheel muni advice? 
great guide though, very comprehensive and plenty of info about different off-the-shelf munis!
Because most beginners don’t ride 36er muni 
Big wheel muni advice:
Buy the strongest, lightest, highest quality 36er you can afford, get brakes and long cranks, get a Todd tire, drop the seat and go ride.
About the only difference in the high end 36ers would be hub width; 125mm spacing for the Nimbus Oracle 36er, otherwise everyone else uses a 100mm spaced hub.
Personally, if you want a disc brake, I would not use an internal hub mounted rotor unless you have the 125mm hub, the 70mm flange seperation is not wide enough to build a strong 36er wheel. Alternatively you can get a crank mounted rotor and run a 100mm standard hub; this is the easiest, esp if you want to run a Schlumpf.
What about Quax munis
I’m working on that. I think I’ll also do another about street/trials/flat unicycles.
Not a bad write-up, although I found it funny where you put the bit about all aluminum frames being 27.2 mm except nimbus and Quax.
Good job.
@mod (if there is any): Would it be possible to make this thread a sticky in the products forum?
What about learners!
I will do as much as I can. I just started with munis because someone asked for it.
+1
I’m tired of seeing so many people asking “which unicycle should I buy?”
I applaud you. Great thread(s) for the newer guys asking the same questions. A sticky would be nice! 
Thanks for the wonderous guide!
I’ll be looking forward to your street/trials/flat unicycle guide!
I kinda forgot about this for a while but I am now working on reviews for all other unicycles.
I would appreciate it if people PM’d me their feedback on STOCK unicycles, especially 36ers. Also feel free to send your feedback on individual parts such as: tires, frames, cranks, etc.
If there is anything you would like a review on feel free to ask here.
I think Kris stopped producing the xcountry rim for his 29, no? You can still get them though…
I have one on my KH29 custom I made from used parts a few years ago, I stopped seeing them sold back then so I would assume they have been off-market for a while.
Anyone else have any feedback?