This is what Qu-Ax said regarding the crank and bolt:
"we do assemble the unicycles best we can, but especially after the first rides, we strongly recommend to check and retighten all bolts.
There is not much load on this bolt, it is just to put the crank into place - so it is possible that it gets loose. I am sorry, of course it’s not normal, but it can happen.
We will add one to your next shipment, please remind. Until then, no problem to continue to ride it."
I do wonder if they saw the picture of how far it sticks out.
@UniMyra, can you check/get your friend to check that the crank is correctly seated against the spacer and that in turn is snug against the bearing, as well as checking what the other side looks like?
What about using blue loctite?
That’s very likely the problem. On a new unicycle, the bolts usually come with some sort of thread locker on them, but how many of us change cranks repeatedly without reapplying it? I know I do.
Slightly off topic, but there was an additonal problem. This is his (the friend) bearing after a few weeks use. How is this possible? Overtightened bearing cap? Heavy rider (2 meter tall)? In 11 years I’ve never had a bearing looking like that.
He is already buying new bearings by the way, before anyone suggests that! 
Is there any progress in the translation of his book?*
*conclusion of 2m tall friend
LOL, I kind of figured one of you would work out who this friend was at some point.
Very off topic now but since you asked, I suspect he might still be struggling with the translation of his latest kids book 
P.S. I have not read that one yet but I feel like I should!
Nevertheless, have I won a free copy?
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…
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.
