40mm bearings for a KH Moment

I too would like some of these bearings. I think the concensus is that they are not made.

It is one issue if the bearing caps “just fit”. This issue determines if one can assemble their unicycle at all.

It is an entirely different issue if the caps fit well enough that they don’t put uneven pressure on the bearing’s outer races. This issue determines the useful lifespan of the bearing.

Unless the cap is designed to fit the bearing (not “just fit”) it is likely the bearing’s life will be shortened. The question is, how severe is the effect…

I used 42 mm bearings in a 40 mm frame for a long time with no problems, not they are in a 42mm frame and are still going strong.

Why don’t they just make all frames with 42mm holders as a standard, and have them come with the 1mm thick circular shims for those hubs that use 40s.

Because that makes sense.


and wouldn’t cost any more to make, either.

Actually, the standard bearing size is 22x44x12

I think a special size was made up for the 22x42 ISIS uni size, unavailable at bearing houses, etc. They would have used 22x44 for the uni ISIS standard, I guess, except the manufactures didn’t want to redo all their frames.

17x40, and 20x42 are standard sizes. I think only the Torker DX series, and the ISIS use a custom run of a unique size.

The market is likely just not there to justify the cost of making 1000 22x40 bearings. I haven’t researched this though. I am just guessing that you might have to sell hundreds for 10 $ each just to recoup the tooling costs of the first batch.

This question has been raised in several threads. Currently it cannot be done.

The general explaination is that 42x22 bearings are common, and 40x22 bearings are not. I guess the fact the a new thread is started about this once every couple of weeks is not proof enough that there would be a market for the bearings if KH were to do a limited run of them. Maybe Nimbus will answer the call?

I would have bought Moments if they’d done the limited run. Instead they lost my business. I’ll still consider it for my spare muni if they were to make 'em, though. I could always use to beef that wheel up. Otherwise I have to go with the twice as expensive profiles.

It is I think because the 22x40 bearings would be too thin and not last long enough. ISIS on bikes had big problems initially with teeny weeny skinny bearings that lasted about a week, and the unicycle people wanted to avoid that.

People with machined 40mm bearing holders, possibly the best solution is to get them machined out to 42mm, I know people have done this with some frames, surely no frame is built to such tight tolerances that there’s not enough material between the bearing and the bolts at the side to fit in a 2mm extra diameter? I reckon it’d be easy enough on the 40mm machined bearing frame I’ve got (DM).


I’d argue that if 2mm makes such a big difference that 22x40 bearings are too thin vs 22x42 than that same 2mm difference will toast a frame orginally made to 40mm specs. Either 2mm matters or it doesn’t, I’d think.

2mm in the bearing vs. 2mm in the frame. The frame is just a bit of non moving metal, which doesn’t wear, whereas reducing the size of the balls in the bearings (by 20%!) reduces the size and strength of the moving parts that make your wheel turn round / stay on.

I’d only worry much about it if there actually wasn’t a bit more than 1mm space inside the bolt holes on the bearing holders.


Mmmm… true enough, I guess. I still wouldn’t want to machine my frame though. :slight_smile:

Maybe profile will solve the problem by dropping their prices in response to the moments and then no one will worry anymore. It was already explained to me why that’s never going to happen, but a guy can dream, eh?

actually, take your bearings to an industrial bearing shop, and tell them you need new bearings w/ the same inside diameter, and same width, but an o.d. of 40mm. chances are, they’ll be able to get something that will work. i’m not 100% positive, but i have done this with bmx hub bearings when i needed to convert the hub to run a different size axle.

Yeah I’d quite like to get a hold of 40mm bearings for ISIS hubs too…

my Ti frame uses lollipops and 40mm is all it’ll take inside, and those are a tight fit too…


Since your frame uses lollipop bearing holders, bearing width doesn’t matter as much, right? If you just add some spacers on the hub so that the bearings will press against the lollipop holder the following might be able to work in your case.

22mm ID x 40mm OD x 7mm width

Or you could use two per side if your bearing holders are deep, cause then the effective width of it would be 14mm, only 2mm wider than what usual uni bearings are.

I wouldn’t give up if I were you. I had a similar question, but it was for an ISIS 42mm hub to 41.2mm Profile bearing holder. I was directed to Jenson USA and got the exact bearings I needed. I rode my new setup in Moab, no problem.
I would recommend emailing Jenson USA and asking them. They’re good about answering weird questions.

Good luck!

Edit: Looking back at my thread, Kris Holm said there weren’t any 40mm outer diameter bearings with the correct inner diameter, and I’m guessing he’d probably know as well as any one. But his solution was to find 37 mm bearings and shim them up. If it’s good enough for him, it should probably work for you as a temporary solution.

I thought profile were 40mm, just like the suzue.

Profile are 1 5/8". I was thinking they made a 40mm also.

They do.