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