Getting the crank arm off is no different from a bicycle; you need a crank-puller tool.
BHPian supermax recently shared this with other enthusiasts:
Last year, when I was learning to ride my unicycle on light off-road trails, the left crank-arm started to wobble faintly. As I continued riding, the wobble got more and more pronounced and when I stopped, I saw that the crank-arm bolt had worked itself almost completely loose. Since I hadn’t carried my extra large Allen key (M8), I couldn’t fix it on the spot, so I had to stop mid ride and drive back home. Once home, I quickly tightened up the bolt, but when I took it out for a test ride, I found that the wobble quickly returned, no matter how much I torqued up the bolt. A local bike store diagnosed it as a busted crank arm, and since unicycle crank arms are not the same as bicycle crank arms, I needed to order from the unicycledotcom affiliate in Sweden. When I checked their website however, I saw that they had no stocks of the 125 mm cranks that I had on my unicycle, and when I called them, they said they had no idea when it would be back in stock either. I remembered then that I had a set of 150 mm cranks that I’d never used, and I thought I’d give them a shot.
Getting the crank arm off is no different from a bicycle; you need a crank-puller tool and before long, the 125 mm cranks were off. When I inspected them however, nothing seemed amiss, so I was a bit puzzled. When I tried to install the 150 mm cranks, I realized what was amiss; the screw seemed to be partially stripped, but the hole on the hub was in much worse shape, as the thread around the entrance was destroyed, probably when I rode a bit after the crank arm had loosened and started to wobble. Frustrating as this was, there was nothing I could do with a trashed thread till I got my hands onto a thread tapper, to fix the stripped thread.
A visit to the local tool store (‘Biltema’) the next day gave me what I needed, an M8 thread tapper, and before long, it worked its magic, and I could get the bolt into the hole again.
The M8 thread tapper.
The M8 thread tapper, up close.
When I installed the 150mm cranks, I discovered that the crank arms were way too long for my height, as my legs couldn’t even reach and touch the pedals when the crank arms were in 12-o-clock and 6-o-clock position. The saddle was already all at the lowest possible position without the saddlepost hitting the tire, so if I needed to lower the height any more, I’d have to saw down the saddlepost. Since I didn’t want to do this, I decided to order 114 mm cranks which were still available on the web store. There were shorter than the 125 mm cranks I’d ridden the 24″ unicycle with, but I was used to riding with 110 mm cranks on my other 29″ unicycle, so it should be okay, I thought.
The red tool is the crank puller. The black crank arms are the 150 mm square taper cranks while the chrome ones are the 125 mm crank arms that were originally on the uni. On the uni in this picture are the new 114 mm cranks.
The new cranks arrived in record time and as expected, I was able to ride quite well with them, though the ride characteristics were quite different. In fact, I liked it better than with the 125 mm cranks, as the smaller tighter circle my feet made seemed a lot smoother than before. The bad news though, was that the wobble was back, even with the new cranks, letting me know that the problem had always been the hub; it was simply not capable of withstanding the torque I applied at the crank arm any longer. While the thread tapper had helped, it was still a no go, so as a final Hail Mary, I applied some superglue to the threads on the crank arm bolt and drove it in quickly and tightened it before the glue set. Left the uni to sit for a while and then tried it out gingerly, wishing I’d not hear the dreaded creak that signified that the bolt was unraveling, but the glue and the bolt held, at least for now. I rode for a while till I tired myself out, and called it a night. Here’s hoping that the fix holds for at least a while longer, as this is a unicycle that I like to ride on the snow, and like the characters in the series ‘The Game of Thrones’ often pointed out, ‘Winter is coming!’
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