Can't keep cranks tight

I have a newly acquired Koxx One and I cannot keep the crank arms tight.

They were loose upon receipt and I felt that I had tightened them as best I could, but after a few pedal strokes, they did not feel right and I had to tighten them again. Did I damage the crank arms by not having them tight enough? They will only go one so far while the splines are still showing and the spacer ring has a lot of wiggle room. I have removed the cranks with an isis crank tool and reinstalled and even tried Loctite 242 on the crank bolt.

Would the crank get damaged before the hub? I want to know if it is worth a new set of cranks. What does crank arm damage look like?

Any ideas would be welcome.


How long is the hex key you are using. A standard short 8mm key is not long enough to provide the required tightness.

Ideally you need something like this.

The cranks should tighten all the way to the spacers. With a long hex key, don’t be afraid to go to town on the force you apply, it needs quite a bit.

If this doesn’t help or you have already done it, you may have damaged the crank arms. With ISIS, once they are damaged, there is nothing that you can do. Loctite on the crank arms as well won’t hurt but if they struggle to go on, lithium grease may help.

One option would be to use wider spacers, so that crank arm is blocked to the spacer by the screw. Otherwise you are pushing them too far on the axle. It might not help if they went too far already, but is worth trying.


This is yet another thing I am confused about. What happens if the crank arm does not tighten down to the spacer? Can that cause the crank bolt from never staying tight?

Hi there

When I bought my Quax they didn’t come with spacers and it always has worked fine (the cranks don’t go all the way to the hub, there is plenty of space to fit a big spacer between them and the hub). In my experience the cranks usually come loose very quickly when first used, I often have to retighten them a couple of times more after each small ride before they stop coming loose. Quite a few times I have ridden my unicycles with loose cranks before I noticed it: so far I haven’t managed to break/ruin any of them (neither the hub or the crank). So I’m guessing that whilst you didn’t do anything too extreme or left them loose for too long thay are probably ok.

Use a torque wrench and take it up to 25 lbs. They should stay tight. Make sure the threads are clean, and use blue Loctite.

What Lance said. If you aren’t using a torque wrench, it’s almost guaranteed that they aren’t tightened enough. 25 ft-lbs is way tighter than most would guess, and damned hard to get in fact with an ordinary Allen wrench, even the T-handled style.

Thank you!

Thanks everyone for your replies and ideas.

I am struggling with what to do with this unicycle. It’s a 19" wheel trials that came with 160mm cranks. Those are huge!

I am debating getting a shorter crank set, but I am also finding info on Koxx One cranks somewhat confusing. Is their ISIS compatible with others or am I stuck with Koxx One ISIS cranks?

If It needs to be Koxx, my buying choices are somewhat limited.

The ISIS interface on the K1 cranks is the same as any other. I have a set on my Oracle hub, and I occasionally swap them out with Moments. No problems.

Just to add to what Lance said. The early Koxx cranks were a little different than most, and gave some people problems on different hubs. All of the info you read about Koxx incompatibility is those earlier ones. Yours shouldn’t have any problems since that all happened long before Koxx went belly up.

My problem was some grease had gotten on the threads.
Even red Locktite (“permanent”) & 65 ft-lbs (the max for my hub) wasn’t enough and eventually I broke off the bolt.

Cleaned the threads, new bolt, 45 ft-lbs & blue Locktite and it’s never loosened again.