Can I fit a Schlumpf on my Onza?

I’ve been asking a lot of Schlumpf questions lately because I think I must have one.

It’s just occurring to me that I could save a bunch of money if I can build a new wheel and fit it into my current ride, a 24" Onza muni, as opposed to buying a new KH24.

As far as I know it has:
20mm diameter 36-splined hub with a dual keyway.
Bearings: 20 x 42mm Sealed bearings.

But isn’t there more to it than bearing sizes? Spacings are important, right?

Will a Schumpf fit in this frame? Is there any reason not to?


You will need machined 42-mm bearing holders. As far as I’m aware, people have had problems even with the non-machined 42-mm bearing holders as they are not quite round, so you’ll have to have something like a KH frame if you don’t want to pinch the bearings on the hub, especially the fancy torque bearing.

I don’t know if nimbus is making something cheaper than the KH frames that you might be able to use.

So if you were going to re-use parts from that unicycle, you’d need a new frame and cranks. The schlumpf is ISIS splined, not 36-spline kh/onza… seatpost might be an issue too, depending.

It probably would fit, but the general consensus is that it should really only be used in a Kh frame. What do the bearing caps look like?


It has pressed bearing holders.

Pressed bearing holders are no good as there will be pressure points on the bearing and the hub will quickly be destroyed.
Most machined bearing holders will be up to the job: Nimbus, KH, Triton…
If you were desperate to keep the Onza you could have a welder set up a jig (as the bearing holders need to be accurately aligned) and replace the bearing holders on your Onza.
The cost could be as high as a new KH, which is a huge improvement over your Onza anyway.

Thanks guys! Great info.

I’d like to avoid that!

Nope. I just didn’t want to spend an extra $600 if it wasn’t going to really get me anything significant.

Looks like I’ll be going with the KH. But what is it about the KH that makes it such an improvement over the Onza?
Seat? Aluminum versus Cro-Mo?

It’s just the machined bearing holders that makes the difference, not the materials. There are strict tolerances (so I understand) for the geared hub that are not necessary for conventional hubs.

Every part is stronger.

You would need at minimum new cranks, frame, and spokes. The frame would have to have machined 42mm bearing holders, like others have said.

I’m not sure if there’s a suitable nimbus option, but then you might be able to keep your seat, seatpost, rim & tire, and pedals. You could probably save a couple bucks, but the setup wouldn’t be as solid as the KH option.

Yes it’s the type of bearing holders that are vital but what’s better than on the latest KH compared to your Onza includes (but is not limited to):
saddle design
seatpost strength
frame weight (Aluminium v. steel)
rim strength
rim weight
New tyre and tube will be better as they’d be new
spokes & nipples and hub will be changed regardless, which leaves the seat clamp & rim liner which could be of similar quality I suppose… I think the KH seat clamp would’ve been redesigned since your Onza’s.
Actually the rim liner is totally different on the KH due to the cutouts so you can’t do a direct comparison.

Did I miss any components? Let me know if you want more convincing :slight_smile:

Darn, Dave made me realise I missed out cranks, which wouldn’t be compatible with the ISIS KHU Schlumpf hub…

Gosh… I didn’t realize what a pile of crap I’ve been riding! :D;)


I had an Onza for a while and it was a good ride. The frame is actually very light, in fact at the time the stock Onza was lighter than the stock KH (first aluminum one). The seatpost is 27.2 just like KH, and the seat is the same as the old KH Fusion (pre-freeride).

So if you go with the KH frame you could use your seat/seatpost, and pedals. I would recommend getting a new rim anyway though. The rim on the Onza is pretty narrow, and you will notice the improvement with even the Nimbus MUni rim.