Technical - Q-Axle Crank Interface

Do they live and ride near the sea/on the beach/somewhere with regularly salted roads?

Pressure washer to keep things clean?

Unicycles require minimal maintenance, but pressure washing around the bearing caps tends to just push dirt into them, and they hold water so do require checking and coating with grease to keep things in order.

That looks like rather a lack of periodic maintenance and potentially iffy cleaning practices leading to premature bearing failure.

Maybe this should be moved to a new thread on unicycle maintenance though.


Does anyone know the difference between the black spacers (used with the standard gray cranks) and the gray spacers (used with the black ZeroQ cranks)?

I bought some ZeroQ cranks and didn’t think to get the spacers. But…

  • the interface on the new ZeroQ cranks seems to have the same dimensions as my old cranks, and they fit perfectly (as far as I can tell)
  • and my existing spacers are gray, not black. Did the color change at some point? Or did the “standard” crank design change, and need a new black spacer?

So confusing!

BTW my bearings, which I haven’t touched since I bought the uni three (?) years ago, looked pretty good. No internal rust, and still some grease in there. One of the bolts that hold the bearing caps in place had rusted solid to the nut, though.

Probably best to measure them to check.

Apparently you need the 5.8mm ones on the older silver cranks, and 4.8mm ones on the black zero-Q cranks.
Silver spacers for black cranks, and black spacers for silver cranks.

I’d say it’s less confusing than ISIS spacers though, where you just need whatever spacers are appropriate for the combination of parts you have, which is generally determined by lightly putting a crank on and measuring the distance to the bearing (then you want a spacer that’s approximately 2mm smaller than that gap).

Thanks for the info! I didn’t see anything on the qu-ax site.

Turns out that I have the 4.8mm gray spacers, which I needed for the new cranks. So either it came with the wrong spacers, or qu-ax has changed something since I bought it.

Actually Sep 2016 - time flies!

I suspect there’s another clarification somewhere, but the product pages give that information:

Update on the heel kicking cranks

The grey QX cranks can easily be modified by filing away some of the excessive material on the rear end. E.g. like this:

That provides some improvement on this issue.

Comparison black versus grey cranks

I got the chance to thoroughly test some black ZeroQ cranks of the same length, 137mm.

Conclusion: The black cranks are simply better in this regard, as expected. They are way less likely to kick my heel off the pedal, even when compared to the modified grey cranks.

Bearing update

Qu-AX has promised to improve upon the (bad) Q-axle bearings. Apparently it delivered.

First impression of a new Q-axle hub bought this year: Its bearings feel smooth and ain’t got the “sandy feeling” like some previous generation had.

I can’t judge longevity or robustness at all. It’d be surprised if they came close to ISIS bearings’ quality. But I have hopes that they’ll at least last longer then previously.

Axle screws

Those two big golden axle screws (“adjustment caps”) now come with hex drive.

Crank choice

After many years still no improvements regarding crank choice unfortunately.

It’s funny, the ball bearings are being improved, but Qu-ax always denied that there were problems. This is exactly why I advise against it. You will always have to buy these bearings, no matter how good or bad they are, because there are no alternatives. This also applies to the cranks or seat posts with their special diameters.

Why should there not be alternatives? These (q-axle as well as ISIS or cotterless) are standard industrial bearings. You can buy them at almost every bearing seller. It’s just {inner diameter}x{outer diameter}x{width} plus some additions for seals (mostly 2RS for sealed both side with lip seal). And of course you can always choose to buy cheap china bearings or high-quality bearings of well known manufacturers.

I have to revise myself. I just realized, that none of the renowned companies produces this size.


I was going to say, I’ve never been able to find a suitable 24x42x12 bearing replacement that’s not from Qu-Ax.

That said, ISIS Bearings are also not standard sized bearings. Only the ones for cotterless are a standard industrial size.

The funny thing is, there are standard sizes that are not far away from the original q-axle dimensions and can handle the same max load as the originals: 61905-2RSR or 6905 2RSR. They are 25x42x9 and would need shims on the inner diameter and the width but are produced by most of the high-quality manufacturers.

I also found similar ball bearings, but not identical ones. Imagine it is Corona and the ball bearings are sold out. You have no alternative and hope that they will be produced again at some point. I therefore only recommend riding unicycles that allow a choice of components. That’s one reason I don’t ride a Q-Axle or a Kris Holm unicycle. For Kris Holm (they are very good unicycles) it is the cranks. If you need replacements and they are not available, you have no alternative. However, unlike the ball bearings, these cranks practically never break. (Sorry my english ist not good)

you mean like ISIS-bearings are not available in the US right now? :slight_smile: This can happen to any component these days…

I think you’re perhaps intentionally missing the point.

Despite not being a standard industrial size, 22x42x12 bearings are available from a multitude of different suppliers, not just one unicycle manufacturer.

Admittedly many of the more specialist suppliers will charge around $20 per bearing but even in this pandemic if you’re prepared to pay that bit more you can get them. As an example, has a selection in stock that they can ship quickly around the US.

The bearings that are required for the Q-Axle hubs currently seem entirely unobtainable aside from via Qu-Ax.


Actually it looks like you can get them from China in about a month. $1.99 each plus $2.61 delivered to your front door.

Or do a Google shopping search for 6004-22-2RS for other quicker and reasonably priced options. Just be careful that they are not the standard 20mm ID.

Yes, I had seen a few of those, but was excluding them as they’re not local (US) supply. You can get such bearings from all over if you’re willing to wait for the shipping!

Apparently Quax kindly offers “industrial bearings” (“Industrielager”) for Qaxle hubs.

First off, a bearing exclusively produced for consumers isn’t an industrial bearing. Second, if it weren’t, I’d love to know in which industrial application a bearing of that quality was accepted.

Is this a marketing lie by Quax or did I miss something?

I think the definition of industrial varies by country.

Industrial means pretty much sod all over here.

In german bicycle jargon, cartridge bearings (as opposed to the multi piece cone types you would commonly find in bike hubs and pedals) are often called “Industrielager”.


Clearly weight does not effect your riding .skill trump’s weight and clearly you have skills