I guess that the crank bolt worked its way out. I was practicing hopping and noticed it after I had been hopping for a short while. I tightened everything back, but now the right hand crank still wobbles a bit.
The crank arms are aluminum ISIS (cheap ones that came with the Sun unicycle I have). The hub is a Nimbus 36H (CroMo). I’m sure the crank is toast, so I ordered another set. I’m hoping that the hub isn’t damaged too …
Do you guys put thread locker on your crank bolts? I was considering that …
I put thread lock on mine but I take a minute before each ride to check my cranks, pedals, saddle seat post and touring bar. I give every thing a good wiggle and tighten if loose.
The crank bolts shouldn’t just come loose. If it’s a cheap unicycle, they often come without crank spacers.
The ISIS interface is designed to be used with spacers. If you don’t have them, the cranks will wear out prematurely. Get a selection of different size spacers and use the biggest ones that don’t make the cranks wobble. Once they start moving again, fit the next size down and so on.
To be fair: I didn’t use a torque wrench. But after having to buy new cranks, I’m going to use one now.
Does anyone have a picture of one of these spacers? I got my hub from UDC, and I don’t think they sent one (or, they sent one, and I didn’t know what it was, and lost it - which might be a more likely explanation).
Torque wrench is not important, spacer is important. It’s a small ring that goes on the hub, between crank and bearing, the crank should push up to it and be preloaded against it slightly.
As Ed says, if the crank wobbles the spacer is too large and if the crank does not sit against the spacer, it’s too small. I’m sure UDC can give you advice on which size should be a good starting point for your hub and crank combination.
You can make your own spacers by cutting a piece of 27.2 mm seattube to the right size.
No, you should have grease on the threads to ensure appropriate torque. Thread locking compound is for bolts where they want to stay in position with a low torque (like the bolts holding bearing caps on).
In terms of figuring out spacer size, a better way to judge them is to push a crank on by hand (with no spacers) and measure the gap between the bearing and the crank. Then get spacers that are 2-3mm smaller than that. If you’re using softer aluminium cranks (anything other than 6066 or 7075 probably) then go 3mm smaller. Steel I’d go with 2mm.
It’s also highly recommended to never take cranks off once installed unless you absolutely have to. The interface wears and deforms a little every time you install and remove them, which leads to things loosening and you needing new cranks or at the very least new spacers over time.
Remove your pedals if you need to make the unicycle narrower. Grease and pedal washers (on aluminium cranks) also recommended there.