Fall 2023 KH unis are here (introducing Boundary Cranks)

Hi All,
I’m excited to (finally!) announce the release of an updated KH lineup for Fall 2023! New to the range are the Boundary cranks and hub, which will replace the Spirit cranks and hub. Boundary cranks build on the proven Spirit cranks geometry with several improvements.

The major update is to the spline interface, now with Q-Axle micro spline. Qu-Ax’s innovation on the hub has proven itself - lightweight (380g) and strong with extended use, and KHU has adopted the same hub design. For those unfamiliar, the spine is parallel (not tapered) and secures with pinch-bolts on the crank – it’s easy to install and remove without the wear and tear of a tapered spline. The Boundary hub is 100 mm bearing-bearing width and is 36-hole.

The Boundary cranks are forged from 7050 alloy with 8 mm outwards flare. That is 4 mm less than Spirit cranks. I’ve ridden with these cranks for a year and really like this profile – slim with clearance to avoid bashed ankle bones or heel clips. Boundary cranks are available in these lengths: 110/127 mm (373 g), 117/137 mm (414 g), and 127/150 mm (444 g). The 165 mm version is discontinued. While this may make a few riders unhappy, there’s too little demand for it anymore, and eliminating it shaved a few grams off the weight by designing the forge tooling for a 150 mm length.

The KH20, KH24, KH27.5, KH29 and KH36 are all KH blue and have the Boundary Cranks and hub – meaning an internal disc brake (excepting the KH20). While I have been happy with the external disc brake, this brings the KH range into compatibility with the hub-mount standard. Too many “standards” is a real issue in the cycling world, and I think our sport is better with compatibility across brands.

Check Unicycle.com franchises and Qu-Ax dealers for stock - available today in some countries and expected to arrive next week in Europe and the USA. Check them out and let me know what you think!


Really like this line up, Kris. Very clean and seems like a nice step change in the right direction.

I’m not personally in the market for a new unicycle - but these would defo be on my list if that changes.

I guess the options on ISIS cranks for Schlumpf riders are pretty wide ranging and I can’t see Spirits disappearing from stock overnight. But it’s sad to see them being discontinued. Is that a full on - no longer made affair, or might there still be small trickle runs of them made for those that want/need them?

I get it probably is a “no” to that as production costs will prohibit.

I’m going to say it now even though I picture it never coming to pass - but a Q-Axle style Schumpf hub would be interesting. It might allow for a beefed up shifting rod.

Anyway. I digress.

It’s a really nice line of of unicycles, cranks and hubs. Congrats!

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Does this mean they will no longer be manufactured? I agree with mindbalance in suspecting they will not. If that’s the case then does this change potentially effect all prior KH unis whose owners want to use a disc brake? When it comes time to replace broken or worn cranks the only option with a disc is Spirits.

Would an inboard disc hub (Boundary/Q-Axle/Nimbus) work in a right-tab frame? Seems like it might but the wheel would be mounted backwards from a left tab frame and the caliper mounted upside down relative to a left mount.

Oh well, I guess every system/design eventually becomes obsolete. Let’s just hope there’s a good stock of Spirits in warehouses.

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Concern is mainly for Schlumpf hub which is ISIS and would need a complete re-enginering


The short answer is no - there won’t be a complete re-engineering needed. There is a relatively ingenious solution that we can add to this thread shortly. Those who have already purchased or are planning to get the 2023 ISIS KH/Schlumpf hub will be OK too. More to come.


These look great, but I do wish there were a 32H version of the hub. My last two wheels were 36H Q-Axle hubs built with 32H carbon rims - because I could only find 32H bike rims, and because Qu-Ax only offers a light duty aluminum hub in 32H.

Building a mismatched wheel isn’t a huge problem if you do it yourself, but I don’t think many shops would do it.

My experience is that 32H is plenty for what I would call “aggressive cross country” riding (including over a decade on a 29" 32H KH rim!). It would be really nice to have it as an option for people looking to put together a high quality custom wheel.


I’d second the 32 hole option. I feel 36 hole on complete unis is fine, but most people that build their own wheels want 32 hole if they can get it. I have a had lots of people reach out saying they can’t find a reliable source for 36 hole rims.

I have 32 hole wheel built, and found 2 more hubs I’ll be shipping from overseas just to have them on hand for future wheels since they are unobtanium at the moment.

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KHU does not produce a 32 hole hub, but - note that Qu-ax does produce a 32 hole disc version of the Q-Axle hub that would be compatible with the Boundary cranks and the rest of the KH setup.


Will the new cranks ever be made in single hole?

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Over a decade of experience with the double-hole Spirit cranks has shown the geometry to be strong with double hole, and it adds versatility. Currently we plan to stick with the double hole versions.


Will Spirit cranks continue to be manufactured?

No, the Spirit cranks will be discontinued.

This lineup almost seems like KH is going to leave most of the urban disciplines behind. Would you say this is true? looks like no more rollos. and I imagine urban riders would complain about the crank bolts on the end of the boundary cranks. Pretty good for trials, obviously. The ability to take the unicycle apart easier and the lighter hub looks incredible. This looks like KH is becoming a dedicated muni brand?

So in a way, the KH/Onza hub of old was a bit ahead of its time… :stuck_out_tongue_closed_eyes:

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It’s true that the Boundary cranks won’t fit Rollos and the testing has been more for muni and trials. In actual practice I’m not yet sure it makes as much difference for flatland as one might think. My guess is that opinions are going to vary and all of them are going to be strong =). This is something I’d love to get feedback on.

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It makes a difference as soon as you plan to do any roll tricks (which most flatland riders will). Rollos on the Zero-Q Q-axle cranks make them okay to do rolls on, without them I’ve found it tricky.
With no rollos, more rounded edges and slimmer profile the boundary cranks will be pretty tough for rolls and with no amazing crank upgrade options, the KH 20" is pretty much not an option for flatland riders.

Love the Q-Axle system for Muni and I’m glad to see it in the KH lineup, but on the 20" it makes it pretty much a trials uni only.
BTW, the next Qu-ax innovation others should really start to adapt more is larger seatpost diameters. Seems like almost free weight saving to me.

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I wonder if you could just slap the qu-ax Rollmops onto the new boundary cranks. Seems like it ought to be possible. You still have a weird lobe on roll side though

Just going to add - I confess to being mightily curious on this point :nerd_face::gear:

It’s great to see these hubs have been considered and I always love an ingenious solution.

Hope you’re able to share more soon! :grin:


Since the ID of q-axle is bigger than the OD of ISIS, an adapter shall be possible.


Totally can see that.

I’m still curious / interested to see how it will interface and secure fast to the axle and align with other parts of the schlumpf design.

I’m part hoping it will allow for a way to mount cranks that protects the hub and its axle area. Not saying the current way is bad but it’s my least favourite task: mounting cranks on a schlumpf :joy: