K1 Cranks wobbling (laterally)

One of the Koxx One 140mm cranks (“reinforced”, so-called) on my 20" K1 uni is wobbling horizontally, and seems to be loosening laterally (from the perspective of riding the uni) slowly over time. It’s wiggling slightly away from the uni when I ride it, and I’m worried that it might get worse if I keep riding it. If it’s stripping out, should I just buy ISIS cranks and replace the cranks or should I try to fix them (if so, how?) There’s a hexagonal screw on the crank, would tightening that do anything? Because it’s only loosening laterally, it doesn’t seem to be a problem with the threads.

FYI- It’s gone through a lot of drops, falls and bangs.

Thanks for any help! Can’t wait to get back on.

You should definitely tighten the hexagonal screw if possible.

yeah that happened to my k1 street cranks, tightening the bolt should do the trick unless it’s been damaged already

Funny I found this thread…my wife had the same issue with her k1 White Russian. It kept making a thumping sound/feel. When I tried tightening the bolt, it wouldn’t go any further.

My Siberian friend, if you can’t tighten that bolt any further, look closely at the inner section of the axle/hub, closest to the crank arm it’s self. On my wife’s, she had a spacer on one side and nothing on the other. Turns out the spacer was keeping her right crank arm from going on all the way. After I removed it (which was a bear because that bolt was so tight) the crank arm fit snugly and we haven’t had any issues since.

Hope that helps!

There are possibly 2 things going on here.

  1. The bolt may be bottoming out at the bottom of the thread. The ISIS bolts come in lots of different sizes from 12mm to 27mm. You can check this by seeing if the bolt bottoms out on the thread before it hits the hub when no crank is fitted you need to put a shorter one in or cut it down.

  2. There is some tollerance miss-match between the hub and cranks. There should be about 2 to 3mm of spline showing between the crank and the spacer when the crank is first slipped on by hand. If there is not then you should fit a shorter spacer in. I wouldn’t recommend not fitting one on a trials uni as it will not be as strong an interface in the long term. We do sell a range of spacers for just doing this - you can even get carbon ones!


You want to tighten those down as soon as possible, the more they wobble the more you are damaging the spline interface on your cranks, if you let them go for to long they are going to get wrecked.

If a spacer is preventing you from tightening the cranks down properly you need shorter spacers. The ones that Roger sells are probably the best option but if you are cheep like me you can grind down your existing ones with a belt sander to make them smaller or use thin slices cut off the bottom of your seatpost (works with KH seatpost, not sure if the inner diameter is the same with Koxx)

Koxx used to have cranks and hubs with dimensions a bit bigger than the ISIS tolerances, They fixed that a few years ago and I thought that all the old oversized stuff was gone by now but maybe you got some old cranks on a new hub.

I have noticed that my White Russian 24" unicycle has a creak that seems to be coming from the left crank (appears when a lot of pressure is put on left crank). The bolt is as tight as possible. Will this become a problem over time?

Thanks for all the help. I’ll try all those suggestions until it’s fixed.

It’s on my left crank too. As BlueFlyer said, it’s an annoying thumping sound/feel. I’ll give an upate on any problems and finds I make. Thanks again.

Yeah bro, I’m no pro at it, but deductive reasoning suggests that if one side doesn’t have a spacer and the other side that is giving the problem does…removing the spacer may be an option. Truthfully, when I finally got that bolt loosened up the crank arm came right off with very little effort. When I reinstalled the crank and the bolt, it fit just as good as the left crank with maybe two playing cards thickness of a gap on both crank arms. Not sure if that’s bad or not, but that’s pretty much how we got it.

Hopefully that fixes it!

Fixed. Here’s how: I just took it to a local bike shop to have them tighten the screw. When he did, the crank screw turned like butter. He twirled the wrench with his finger for a while. Of course, this was free. When we asked if it cost anything he replied, “No. GOD NO!” Haha.

No problems anymore. Thanks for all the help though!

Sounds AWESOME! Glad it works now!