I broke my second Nimbus aluminum post within the past year; the first time was a 25.4mm post on my muni which had seen a lot of hard use, and now a 22.2mm post on the unicycle I just use for practicing basic things like riding backwards or one footed - never anything aggressive.
They both broke at the same place, where the top flange is welded on. They both look like metal fatigue failures starting from the weld.
I’m not going to get any more of this design. I’m trying a cheapo steel post to replace the 22.2, maybe steel won’t fatigue quite so fast. For my other unicycles I’m currently using either a Qu-Ax reinforced post (25.4mm) or the adjustable KH post (27.2mm), which both seem like stronger designs.
The Miyata seat posts used to do that all the time, due to stress from pulling up and pushing down on the saddle. Those were made of relatively lightweight (in mass and quality) steel. We put more up and down force into our saddles/front handles than we may be aware!
Seatposts are by far the part that breaks the most often. Aluminum fatigues over time, Seatpost often produce a very fine example where you can see the zone where a crack worked its way through the part slowly, then snaps of once the remaining material isn’t strong enough anymore.
I had the same seatpost and it snapped at exactly the same spot. I replaced it with a Nimbus CrMO seatpost and wrote up the differences here. Almost two years have gone by since then, and my seatpost has not broken again.
Got a surprise today! Loud banging started coming from the bearing during intense uphill training session. Wheel kept turning fine and when took it off at home, I found this:
Got a pair of new bearings and changed the working one. I have a problem with the broken one though… Can’t pull from the bigger ring because the ring slips off and can’t get my bearing puller to hold onto the smaller ring.
Does someone happen to have a suggestion to easily remove the broken bearing?
Tough one! I guess I would start by pulling out every tool that I could imagine possibly using as a puller or a drift and seeing if I could get any purchase on it with any of them. If not, I would try to remove the balls and retainer and shields, then heat the inner ring with a torch until it started to show some color change and see if I could slide or pry it off then.
The absolute worst case is having to buy another hub and rebuild the wheel, which isn’t the end of the world. It’s a chance to upgrade to an ISIS hub if one was inclined, with the usual caveats about frame bearing holders.
Where it mine, I’d see if I could find a puller that might fit the inner race after the balls and outer race are pulled off. A cheap three arm puller may be able to do this.
If that didn’t work, I’d carefully take a grinding or cutting wheel to the inner race and see if I could split it. I’d use that much heat as a last resort, and only after un lacing the wheel.
Yes. I think it’s called Singapore! It’s hot and very humid there.
Unhelpfully, I was looking at your picture thinking I don’t even have a suggestion to easily remove a perfectly intact bearing. I just got an old Miyata bearing off an old Miyata hub but my “fat” Craftsman 2-armed gear puller is too thick to even get behind the bearing without first working it off a bit. Then you have to protect the threaded end of the axle (it uses cotterless crank nuts). So I got a pipe cap that fit. But then I had to drill a hole in the middle of that, because the gear puller wouldn’t stay in place. Then I had to improvise a vice, since I don’t have a workbench… Basically, it helps to have the proper tools!
My thought also would be to try a dremel or a small grinder if you have it. Not much clearance around the flange, but if you can cut part of it, you might be able to then wedge something in there and break it the rest of the way or something.
I’ve never seen a bearing break like that. I wonder what caused it?
How about attaching a hose clamp around what is left of the outer bearing race. With the clamp tightened down tightly against the balls, you should then be able to use the bearing puller against what is left of the broken other race. Failing that, you’re going to have strip the bearing down so you are left with only the inner race, and pull that off on its own.
I have no idea what caused the crack… Maybe some dirt had gotten between the bearing and it’s holder? If this happens again, I will look more deeply into this. It’s only like 3€ for a pair of 6203 bearings though, so I won’t bother investigating this now.
I had a bearing go on a ride. Unlike you, who are wiser, I had ignored bad sounds for a while. Then in the middle of some muni riding there was a sudden clunk, the wheel went loose and sideways, and a few bearing balls started rolling down the hill. Much better to take a look when it starts making noises!
Quick question. How long do bearings last on muni used about, 5 hrs a week. Months or years. Just got a big trip coming up. Might need to take spares… Thanks
I have never changed any bearings, although I don’t think i’ve done the same sort of distance as you. I did once ride my unicycle into the sea for a bit of a laugh, and bought some new bearings beforehand as I knew the outcome. Bearings were immediately crunchy and sometimes stopped turning, but I peeled the seals back and poured some engine oil in, and they’ve been working ever since… It’s been about 2 years. Never did get to use the bearings (although they came in handy for the final drive shaft in the gearbox of my honda C50 when that broke…)
This isn’t really broken, and i’ll continue to use it regardless, but are anyone elses cranks not at 180 degrees to one another? It’s a very old, probably cheap circus unicycle:
Bearing races are extremely hard and as such, they are also brittle. First, thin it using a grinder. Then place it on a hard anvil and hit it with a hammer and chisel to crack it.
I think some Taiwanese sleeping beauty at the bearing housing welding department didn’t pay enough attention during the construction of my Impact frame.
That’s a bottom bearing holder welded to the left frame leg. So… with no thread on either side I guess I’ll just have to zip-tie the halves together…
I guess I’m not taking my new Impact out for a 360 unispin this weekend…
You could just make like a pressed steel bearing cup and use a nut 'n bolt
That’s a pretty weird defect though. I sort of assumed the part where they weld the bearing cups on is a completely seperate part of the process to putting the frame in the box with the bottom cups.
Most likely the mistake already happened at the station where they manufacture the cups. Because the parts are so alike they probably use the same machine for these parts. If they switch dies and they don’t completely clear the machine (or the cart/bin they collect they bearing cups in), things like these happen.
Wheel kept turning fine and when took it off at home, I found this:
If this happens again, I will look more deeply into this. It’s only like 3€ for a pair of 6203 bearings though, so I won’t bother investigating this now.
