Loose Crank arm

My crank arm moves even thought the bolt is tight. I was hoping someone might be able to tell me what is wrong. I made a short video showing the problem.


It is obvious there is play btween the crank and axle

Looks bad, to be honest. Because the cranks are alum, without steel inserts, they likely wear first. However, in your case, the axle splines don’t look so good.
I kinda doubt that just new cranks would do it, you may need a new hub as well. Sadly, it looks like a new hub and cranks are the only lasting fix.:frowning:

That looks like a qu ax, non tapered axle. The new tapered ISIS parts can be smacked tight together before you put the bolt in, so there is zero play, and no wear. In this case, it looks like the uni was ridden for a good bit of time, with a little play, until it has wore a lot. Sorry about that.:frowning:

This is what you want


Email AEB and ask them if they have a promotion price for this hub set. They sell KH unicycles at about 25 % discount, but you have to email and ask first. I am curious if they will do the same deal for hubs. You seem like the perfect man to find out. While you are at it, ask them how much they want for a KH free ride seat.:slight_smile:


Isn’t the qu-ax 48 hole?
If so that won’t fit his rim.

EDIT: Watched the video, and realized that it doesn’t say Qu-ax anywhere.
Dunno where I got that idea, the uni looks like the nimbus MUni judging by the crappy rim, in which case it could be 36 hole OR 48 hole.

Tell us if you can get a discount on that crankset, cody:D

While you’re at it you might want to get a wider rim too.

I figured it was Qu ax by the 10 splines

In any event, the cost of new cranks is so high, that you should definitely replace the whole hubset.

It’s certainly not any of the big brands, but I’m pretty sure there are other 10 spline manufacturers(torker dx?).

In any case it makes it difficult to find replacement parts.

you are wrong.
you need a new crank arm, it looks to me as if the crank arm has become worn from taking it off too much. i had several sets of cotterless cranks do the same thing.

you know what… swap the cranks and see if that helps… it will narrow it down for you as well.

well, a new set of cranks is 100 $ at UDC

He might get a whole new kit for that much at AEB. Sure, if the cranks were 10 $, like cotterless, I would say maybe try a new set.

Trouble is, the worn splines will mean that there will still be a little play, and he would soon be worst off then now. Because it is not tapered spline, there is no way for a new crank to take up all the slack.

Be sure to grease your crank splines, and don’t ride it if it has play, until it can be fixed.

Looks like one of the new Nimbus standard ISIS unis (which is available w/ a red rim, the Muni comes w/ a black one). On that uni the rim & hub are 48 spoke.

I’m also betting it’s just the cranks. The stock ones are known for bending, but I haven’t heard of any wobbling like that. Maybe you didn’t tighten them all the way when you put them back on after removing them, or some grease got on the threads.

Do what skrobro suggested and turn your wheel around in the frame, so the left crank is again on the left side of the frame. If it is still the same crank that’s wobbling, then you need a new crank. If the other side is now wobbling you need a new hub, maybe cranks too.

I ride with Codybee. I’ve seen this Uni IRL. It’s a Nimbus 29” with ISIS hub, 36 spokes, and 150mm nimbus cranks. It’s also only about month old. I have the same thing with 170mm QU-AX cranks and have had no problem.

I believe the cranks were already on when it cam from UDC. As far as I know the crank had never been off until we took it off to diagnose the problem a few days ago.

It’s hard to see from video and pictures but I think the axle bolt was “bottomed out“. I’m new to unicycle maintenance, but I hope that would be a “new-cranks-only” situation? Neither one of us has ever built a wheel. I don’t think we could replace a hub ourselves. Would a LBS charge a lot for that?

Thanks for every body’s help.

(Cody my sprain is healing fast - I hope to ride soon)

an lbs would charge a lot, but i’m telling you that it is not the hub… and udc should replace it if came messed up.

you need to take the other crank off and see how it sits on that side of the hub.

Trying the crank from the other side sounds like a good idea. Thanks, Skrobo and everybody. Cody, do you want to come over and use my tools. I’ve been looking for an excuse to buy an ISIS crank extractor.

Hey one more thing. When I go to my LBS to by an ISIS crank extractor, How do I ask for it. I’ve only ever seen “ISIS” online. If I say it out loud is it:

“I. S. I. S.” saying each letter individually
“Isis” Pronouncing it like one word. (eye-sis?)

Does it matter?

It’s been a while since I had my ISIS crank off

So I forgot how many splines it was. Well, it should be tapered splines then. Clean it, grease it, and bang it on tight with a soft mallet, or a hammer and block of wood. That should eliminate all play. Do that, and if the bolt is bottoming out, get a shorter bolt from a auto parts store. No new cranks or hub needed I would expect.:slight_smile:

Thanks Feel the Light, but maybe I used the phrase “Bottoming out” incorrectly.

What I mean is the crank goes onto the hub so far that even with the HEAD of the bolt screwed all the was down against the axle there is still a small gap between the HEAD of the bolt and any part of the crank that it might push on. You can see it a little at the end of the video. The axle sticks out a little farther than the flanges on the crank, so when the head of the bolt is screwed all the way down, touching the axle, it is still is not touching the flanges on the crank.

I thought maybe the crank had been deformed by over tightening upon assembly. However, that wouldn’t explain how it got “smushed” beyond being even with the axle. Could it have been screwed all the way in at UDC and then “play” in the crank caused it to crush farther while riding.

As far as I know the thing never creaked. Is a creaking sound only associated with square tapered loose cranks?

that’s agood question I would also like to know

If you beat it on with a mallet, does that eliminate all the play ?

If it does, perhaps washers, or a few drilled dimes may allow the bolt to tighten up against the crank ?

We used my rubber mallet when we put it back on. That got it nice and snug. With out any contact from the head deep axle bolt it came loose again immediately. Washers or something might work but they’d have to have that funny squiggly ISIS shape to fit down past the hub and push on the squiggly flanges of the crank. It would be real hard to find something the right shape.

I don’t have Cody’s Uni with me. He’s at work but I’m going to take the axle bolt off mine and see what it looks like.

Thanks again for everybody’s help.

I checked my N29 out. My QUAX 170mm cranks still have several mm of beefy ISIS flanges to push down on. Why would Cody’s 150mm Nimbus cranks be so different?

Can somebody look and tell me how much flange normally sticks out past the hub on Nimbus 150mm cranks?