Something went wrong today with my QX 36" crank - help is needed

Hi All,

I had a ~20 KM ride today with my 36er when at approx. half way I started to feel as if the pedal or the wheel axis knocking softly at specific point of the crank turn.
When I stopped to check it I was amazed to see that the right side crank peeled off some of the paint of the wheel bearing closure area and that basically some offset occurred in the distance between the crank and the chassis (fork).

I immediately took apart the fork closure around the bearing of the right side and tried to figure out what happened.
I couldn’t find anything that would explain it and still the crank is sitting way to close to the fork after I put everything back together again.

I did notice that the crank screw had something like 0.00001… to be tightened with the Allen key, but it practically had nothing to do with it and no movement of the crank had been influenced by that before or after I tightened it.

I’m afraid it’s something bigger going on here - maybe even related to the HUB itself.

Had anyone ran into such issue ever before?

Thanks a lot for the help :slight_smile:

at minimum your crank has catastrophically failed and needs binning.

does the unicycle have spacers between the cranks and the bearings?

trying to ride on an already damaged crank may trash the splines on the hub needing a full replacement. hopefully the hub is still in good condition

Well the crank seems perfectly ok.

However, if I had wanted to better descibe the situation then my guess would be that somehow the bearing moved along the wheel axis and got too close to the crank’s connection point.
Then in the middle, between the crank and the bearing comes the fork which is attached around the bearing and that’s why it is sitting too close to the crank.
But that’s of course only my assumption.

ok that makes sense, i thought crank moved in, you think bearing moved out…

The attached image shows why neither action should happen. The crank and bearing should be separated by a 6mm spacer on an isis unicycle (that doesnt use moments or have a schlumpf hub). The primary purpose of that is to stop the crank riding up the splines and deforming leaving a wobbly crank.

If the spacer isnt present the problem might be solved by fitting it. or i may be barking up the wrong tree again and if the spacer is present im afraid im out of ideas.

Check to see if the spacing between the bearings is 100mm’s (c-c). If the frame spacing is off it can cause this sort of problem. The bearings may have been holding the fork blades together, and when they finally started to move you noticed the problem. If that’s what happened it was probably like that from the factory, and they should replace the frame.

Of course it does sound like you probably don’t have spacers which would prevent the bearings from creeping even on a suspect frame. Spacers should have been included with the hub, but may not have been. There are plenty of posts where the need for them has been argued one way or the other.

If the frame is off it should be replaced. That kind of problem will lead to premature bearing wear even with the right spacers.

even if spacers are absent, correctly spaced providing the hub suits the frame the frame should be fine and come back to shape fine. Paint off looks more cosmetic than structural.

I have a KH36 i had arrive with a 4mm spacer on one side behind a crank arm and a 6mm spacer the other…

Take your wheel out and see what doesnt look right. Hopefully it will be staring at you whats happening exactly

Hope it works out ok and an easy fix for you. Be sure to share your finding!!!

I guess you all are right, it does seem that the spacer got evaporated, because I have never ever took out the crank.
What’s also been seen is a small offset distance of the bearing from the HUB on the other side which I guess it is because of the absent spacer.

Here are the pictures, for your observation.

The good side:

The faulty side:

Thanks a lot for your help!

Does anyone know where I can find such spacer (other then QU-AX’s factory)?


Good 'ol UDC. Just search for spacer and it should come up.

So, what actually happened was that your bearings slid along the axle, so the frame started rubbing the crank (rather than the crank moving and starting to rub the frame). You’ll need to reinstall the bearing in the proper location; I’d probably try to put it there before installing the crank, which you could do by putting an old piece of seatpost over the end of the axle and hammering. If it’s particularly loose I might recommend green Loctite sleeve retainer.

You can likely get a spacer at a local bike shop, it’s probably the same diameter that they use for headsets.

Thanks, I’ll check it out.

Thanks for the tips!

I think I would want to do a paint job to fix the scratches - got any ideas who deals with it; car paint shops maybe?

Yeah, although to make it look decent you’d probably have to strip the whole thing and re-powdercoat, which would be non-trivially expensive.

Yeah, although to make it look decent you’d probably have to strip the whole thing and re-powdercoat, which would be non-trivially expensive. Although it looks like it’s just on the bearing holder, which would be a small piece you might be able to get them to throw in with something else they’re powdercoating.

I’ve read somewhere that nail polish would do the trick and it comes in various colors so it should be easy to find the right one.
Did anyone have experience with such nail polish to fix paint chips?

I kinda tried it, but the chips are cool

It’ll cover the metal (for a while at least). But it’ll look like nail polish covering metal.

nail polish although usually used on carbon frames it works really not bad. Not many unicycles have clear coat from factory even KH i think its all mixed together in the paint base.
Hopefully you can find a white close. put a few thin layers on it will cover the alloy as nail polish is very think.

If later you want to have the paint the best possible suggest getting it bead blasted taking all the exsisting paint off first before its powdercoated or sprayed. Properly done it soon adds up.
Might be able to tape off the area and match the paint in a spray and blend it in. Acrylic spray is cheap and easy to polish once dry

You might find no bike shops will have anything small enough to space a Isis spindle… Definitely no bike headset will ever be that small. UDC should carry 3 sizes so you can measure up your good side and replicate it. Width wise i mean sorry.

Just spoke with a motorcycle paint workshop - they told me that I have to paint the entire fork, although it’s like 1% of it…
When I asked why, I was told that because it’s aluminium there’s no other way but pilling off all the color layer from the fork and apply the new color layer again on all of it. Or else it wouldn’t work…
The price BTW is rather cheap when taking into consideration it’s the entire fork, approx. $50

Now kind of thinking about it, it may be a good chance to redecorate the fork :slight_smile:

Surprising discovery!

Although the theory made sense - regarding a spacer that got lost, and the picture which apparently showed there is a spacer between the opposite bearing and the crank - well it was not true as I found out just now.

I was at the LBS an hour ago and after taking off the crank and reaching the bearings, we saw that:

1- There is no spacer between the crank and the bearing on the “good” side, it only looked as if there was a spacer (as the axis color is black as the spacer is).
2- There are only spacers on between the hub and the bearing on both sides of the wheel.
3- The “good side” bearing had no movement possible as if it was stuck in its place.
4- The “bad side” bearing had few millimeters of free movement towards the crank (away from the hub).

Apparently, there was never a spacer that I thought was lost and the bearings shouldn’t have moved - but the “faulty” bearing didn’t stay in place and that’s why the issue occurred.

Anyway, I took the spacer from the opposite side and put it between the bearing and the crank and tightened it - the bearing seemed to be moving correctly and the space seemed right.
I will order these spacers (who never been there in the first place) and hope it will allow me to overcome this weird issue.

Here are the pictures of the axis which shows also that there is no “place” for the spacer taken into account (or at least so it seems):