hubs/cranks and stuff

What would you like retailers to say? Roland has been very clear (ok in German) on the forum about the Koxx hub being outside tolerance.

I personally have not notified the forum about the tolerance discrepancies with the Koxx hub. What we did do was issue a gentle warning of none compatibility on our site. Being outside tolerance does not make it any weaker (or stronger), it just causes problems for retrofitting cranks.

It should not be the retailers who are having to do this work, but the manufacturer. Koxx as the manufacturer should be telling the retailers and customers, not the other way around. Remember when Kris had the manufacturing problem with the rim (not his fault but a manufacturers mistake)? He took the responsibility and arranged to get all the affected rims replaced. Koxx have refused to admit that they could be wrong. They were informed in September (6 months ago) of the discrepancies in their manufacture. Here is an extract of what they were told:

“I have then done a dimensional and physical check
on it. It seems to differ from the ISIS standard in 2 small ways. The
fluted length is too short, the ISIS standard is 16.00 +0.5/-0.0 the
KOXX hub measures 14.40mm. The second problem is that the flutes do not
seem to be deep enough. It is very difficult to measure this,
especially with the flutes being too short; but using a pair of good
vernier callipers they appear to be 0.2mm too shallow.”

Koxx’s response was that they were correct ISIS standard and KH, Onza and Quax are wrong. This response forced KH, Onza and Quax to do additional checks on their ISIS which were found to be within the ISIS tolerances.

This is a problem that I hope that Koxx can resolve because it makes it a lot harder for the retailers. The retailers have done everything possible to help this situation by feeding this information back quickly to them.


nope. you can swap out KH moment with qu_ax and onza isis cranks.

KOXX know exactly what the ISIS spec’s are, they’ve been using the exact ISIS interface spec’s on MTB bottom brackets and cranks for years…

When I asked them about the K1 ISIS, they said that the splines were intentionally made a bit fatter to increase the strength, since torsion applied to a unicycle spindle on impacts is far greater than torsion applied on a bicycle’s bottom bracket, given the fact that on a MTB the rear wheel hits first and the chainstay length provides a lever to absorb part of the energy… Which makes sense…

I don’t think they would have «made a mistake» with 3 different cranks and 2 different hubs models… If they want to use their own splined interface spec’s, they are free to do it… And personally, as long as it works well, and it does, I don’t see where the problem is…

However, I do admit that if a splined interface doesn’t match the ISIS spec’s perfectly, it shouldn’t be called ISIS, even if based on the basic 10 spline concept… for the details

Hello Roger,

thank you very much for your post, thats actually the kind of post I was hoping for. The measurement by Roland was the one I was referring to, but (as I understood it) it was just a quick check and not a confirmation without doubt. As we just saw in this thread it was up to now unclear if Koxx was ISIS or not.

Of course the retailers have no fault in this and suffer from the situation. However, if Koxx is outside the specification then it is not ISIS. ISIS is a protected name and using it for a non-ISIS component breaks the license agreement. Selling it knowingly under the name of ISIS is close to fraud (and this is also the responsibility of the retailers).
There have been multiple posts in this forum from confused customers on the matter of ISIS, so the incompability notice is not enough in my view. Why can’t you just call it “Koxx splined interface (similar to ISIS)”.

It’s true that only retrofitting is affected, but this is a big deal for some (like me). In my case it meant that I would have had to shell out more for cranks that I liked less (I wanted shorter ones). I felt really cheated and therefore sold my Koxx Devil (which was otherwise really good) to get a KH20 07 instead.

As I said I had hoped for a post like yours long ago. Why did it take that long to clarify the situation? The behavior of Koxx is in no way acceptable, and Koxx should feel the consequences. I tried to contact the ISIS consortium and inform them of the violation, but their email address did not work. Maybe a retailer would have better luck and other means of contacting them.

Thats interesting! So they either lied to you or in the response Roger spoke of?

I don’t buy the reason though, since the difference seems to be too small for any real effect. And if there was a good reason they could have informed the other manufacturers to achieve compatibility.

Thanks. :slight_smile:

Sorry this wins my favourite post of the day. A few points. Koxx are a trials bike company that have existed for less time than, which is considerably less time than Onza. They don’t make any MTB’s as far as I can tell.

Oh… and how can making the interface 1.6mm shorter make it stronger?

Oh and as for Koxx cranks fitting on everyone else’s hubs… sorry, this is a great comment as well. Of course it does, it is larger! it does not mean that it will give a reliable interface.


Last fall I built a Koxx 1/Truvativ Luftalarm/Large Marge wheelset (it can be seen in my avatar). Everything went together great. When statements came out about Koxx 1 not being true ISIS, I was interested in why. I did read Roland’s post on the German forum (translated by a friend and also remember it being stated as a rough measurement). I then measured my hub. My flute length was 16.0mm (within the spec) and the distance between flutes was roughly measured at 17.3mm (I don’t have a very accurate micrometer).

Since the Truvativ cranks fit on my Koxx 1 hub I assumed that it was within the ISIS specification. I then downloaded the ISIS spec and noticed that the tolerances in the spec make it possible for a set of ISIS cranks to not fit a ISIS hub. At this point I assumed that the incompatibility was due to the tolerances in the ISIS specification.

So it looks like I was lucky enough to have a true ISIS Koxx 1 hub and Roland saw a number of out of spec Koxx 1 hubs. It would be nice to have Roland confirm what he mentioned in the email to Koxx (hopefully in english :slight_smile: ).

I am interested in how widespread this problem is.

Was I just lucky to get an in spec Koxx 1 hub?
Were the out of spec hub’s that Roland measured because of quality issues or intentional?
How many other people have been able to fit (non-Koxx 1) ISIS cranks on a Koxx 1 hub?
How many people have not been able to fit ISIS cranks on a Koxx 1 hub?

It would be nice to get a “clear” answer from Koxx about this compatibility issue. Not just “we are within the ISIS specification”. It would be nice to see proof.


First point : year after year, the KOXX bicycle lineup always counts between 15 and 20 bikes, bikes that use 1.125" headtubes, 68xBSA1.37" BB sheels, 135mm spacing rear hub, etc, are called MTB’s… Let’s not play with words here.

Second point : If you can put your hands on a ISIS BB, and compare it with the K1 hub spindle, you’ll see that the difference is actually noticeable if you pay attention… Of course, even I didn’t notice until I actually tried to fit an ISIS MTB crank on the K1 hub… Removing less material when grooving the spines certainly can’t make the spindle weaker…

Now, was it done intentionnally or not, I can’t tell.

Third point : I never said you should use K1 cranks on other hubs. I would rather even strongly advise against it. Use the K1 stuff as a combo. Just like you can’t use an ISIS crankset on an Octalink Spindle, or why different BMX 3pc cranksets from different manufacturers all use a different spindle interface. If the interface isn’t the same on your cranks and spindle, you’re definitly asking for problems…

I think the K1 hubs are all the same (i.e. all non-ISIS). Probably you are just lucky that the Truvativ cranks are wide enough to fit.

We obviously talk a different language, in the UK MTB means Mountain Bike, not Trials Bike. Admittedly the technologies are similar in this, so it is just side tracking the discussion.

The Koxx interface is 1.6mm shorter than the minimum required by ISIS standard, this of course will be weaker than an interface of the correct length. As it happens decreasing the depth of the splines in this instance is more likely to decrease the strength rather than increase it due it reducing the metal to medal contact area due to the tapered spline design. This is only marginal though.

This is again relatively irrelevant. It is history, it has been done.

Please check the Koxx-one site… You will see there that they are STILL claiming that their hubs and cranks are ISIS. Have they changed them? They have not informed the public. The problem is this confusion, not whether they make mountain bikes or not. If they really are ISIS then there will be cross compatibility with other ISIS hub/cranks, this is why the ISIS standard was set up. If you had a Cotterless crank that did not fit on a cotterless hub you would think it odd, wouldn’t you?

It would be helpful if Koxx made it clear what they are selling? They have obviously told you one thing and us another and the public nothing at all. They are just leaving the retailers do their best to find a solution to this problem.


Thank you again for addressing these issues so openly, that really deserves respect.
As I said, the best way to put pressure on Koxx might be to tip of the ISIS consortium. Maybe they could send some tall guys in black suits to the K1 HQ… :sunglasses:

Clearly not all K1 hubs are the same. My hub has a flute length of 16.0mm and Roland’s hub had a flute length of 14.4mm. Do you consider that the same?

It is clear, that at a minimum, Koxx has some quality issues. I would bet that my K1 hub is within the ISIS specs. From my measurements the flute length of 16.0mm is within spec and the distance between flutes of 17.3mm is within one hundredth of a mm and that is only because I have a poor micrometer. I have fit three different sets of Truvativ Luftalarm cranks on this K1 hub so I doubt I got lucky with the cranks.

Since only a handful of K1 hubs have been measured, a larger sample set needs to be measured before a clear determination can be made about how many K1 hubs do and don’t meet the ISIS spec. I do understand why retailers such as Roger and Roland made the statement about the K1 hubs. If a retailer knows of a potential compatibility issue they must assume that all K1 hubs are suspect and issue a warning to protect customers.

I am in no way defending Koxx! If Koxx designed the K1 hub and cranks to be outside of the ISIS specification they should not be allowed to use the ISIS name. But if
Koxx had some quality issues, like any manufacture has at one time or another, I am willing to forgive them.

It does not help Koxx’s case that they have not provided us with information about the hubs that Roland measured. The only statement from Koxx has been “we are ISIS compliant”, which is clearly not the case with all of their hubs.

The more important question is “did Koxx design their K1 hub outside of the ISIS specification?”.

Only Koxx can answer this question. Until Koxx does they will have fewer customers in the unicycle market.

Oh, O.K, I was just basing my statement on the basis that so far no one fit KH cranks on a K1 hub and there were never any problems fitting K1 cranks on K1 hubs (as far as I know). Please note that the flute depth was also measured to be out of spec (and that probably on every K1 hub). Thats why I said that the Truvativ cranks may be wide enough by design (maybe they are out of spec as well?). But thats just my speculation.

Yes, as far as I know, no one has fit a KH crank on a K1 hub. But also understand that the ISIS specification has tolerances where a crank and hub can both be ISIS and not fit together.

From the ISIS spec:

Max distance between hub flutes: 17.290 mm +0.0 mm - 0.035 mm

Max distance between crank flutes: 17.290 mm+/- 0.020 mm

So a ISIS hub can have a flute distance of 17.290 mm and a ISIS crank can have a flute distance of 17.270 mm. In this case both the hub and crank are ISIS and they will not fit together. I am not saying this is the case of the K1 hub. Clearly it is not, because Roland measured a flute length of 14.6 mm (outside of the spec) and a flute distance that might have been more than 17.34 mm (also outside the spec).

Yes, Roland’s K1 flute distance was out of spec, but please understand that the flute distance on my K1 hub is clearly different than what Roland saw. As far as the Truvativ cranks, I bet they are within the ISIS spec. If the Truvativ cranks were the largest allowed, they would be 17.31 mm. For them to fit on the K1, the K1 would be at most 17.30 mm (+ 0.01 mm) over the ISIS spec but more than likely within the ISIS spec at 17.29 mm.

Since my K1 hub is more than likely within the ISIS spec, I wish people would stop speculating that “all K1 hubs are out of spec”. I will admit that I may have the only K1 hub within the ISIS spec, but one does exist!

The problem is that there is too much “speculation” and not enough “facts”. Most of the speculation is due to Koxx not being upfront about the hubs that were not within the ISIS specification.

Here are the facts:

I own one K1 hub that is within the ISIS specification.

Roland measured some K1 hubs that were outside of the specification. (Koxx needs to comment on why these hubs were outside of the ISIS specification).

Some KH cranks did not fit on some K1 hubs.

Again, I am not trying to defend Koxx, Koxx could clear all this up if they came public with all the information about the K1 hub. But I also am not ready to condemn Koxx. I would like to know the facts before I pass judgment.

Thanks for the clarification. And it is true that Koxx should come forward and help to end the speculations.
I guess the tests that Roger talked about were not only done on a single hub. If the problems were indeed the result of manufacturing variance and not only a systematic derivation, then I just wonder why there are no compatibility problems between K1 hubs and cranks (a friend of mine had to replace his K1 cranks twice without any problems with the fit).

no, they were done on 5 hubs/unicycles, 2 from one batch and 3 from another several months later. All were of similar size; in fact they were incredibly similar. It is interesting that not all are the same. jayhawker, is yours one of the newer batch with the words REINFORCED printed in the centre?


Hi Roger,

My hub has the standard K1 within an oval in the center of the hub and nothing else. I believe I purchased this hub from Roland on August 31, 2006 (if that helps).

Interesting! Testing multiple hubs from multiple batches, all with similar size, is definitely a trend. Would mine have come from a previous batch?

Has anyone been able to test the new “REINFORCED” Koxx hubs?


So have any tests been done on the most recent hubs?

This only seems to have become a big issue since the KH moment hub came out which is probably because of the lack of compatability but since then Koxx have brought out their ISIS light hub, is this ISIS or does it have the same problem?

And Jayhawker, you have admitted in another thread that not all Koxx hubs are the same here

It seems that if the new hub is the same as the old one and is out of spec then Koxx don’t really care about making a hub that is truly ISIS and should stop using the name. If they are making a hub that is Genuine ISIS then people with the old hubs should be allowed to return them.

If I bought a hub sold as ISIS and it did not meet the specification then I would feel entitled to get my money back.


Hi Plumsie,

Today I pulled a crank off my Koxx Devil and measured the flutes. The flute length is 15.9 mm (slightly under spec) and the flute distance (rough measurement) was 17.3 mm (probably within spec). This confused me because as you stated I tried to mount a Truvativ crank on the hub last fall and saw a 1/4" gap. I was expecting to see a flute length in the 14.6 mm range that Roland had seen. I then installed the Truvativ crank and saw the 1/4" gap again. The problem is the spacer was still on the Koxx crank that I had pulled off. When I pulled the crank off and installed the spacer, everything was fine. The Truvativ crank has a collar that looks like a spacer, last fall I must have thought that the spacer was installed.

I purchased the Koxx Devil in the fall of 2005. So maybe old batches of Koxx 1 hubs are closer to the ISIS specification than the current ones. I have considered ordering a set of KH Moment 165 cranks to see if they fit on my K1/Large Marge wheel set. But since UDC is out of stock I will not be able to try this until they get some. Also I don’t want to be the one to say “KH Moment cranks fit on my K1 hub” and have other people try the same thing and fail.


Onza Info

You can go the the below site to see Onza Unicycles.

I have ridden the 2005 model and am very happy with it except for the shape of the crown. The potruding pipes would always hit the insides of my knees or my knee/shin guards and this was quite anoying. Other than that it was a great Unicycle.

If the price is similar go for the KH 2007. If you want to have an less common Unicycle go for the Onza.

The only thing inferior to the KH is that the paint chips and scratches easier on the aluminum than on CroMoly.