The article in the link says the Campy balls had tolerances of 0.001mm. Converting to inches (1mm=0.0393"), that's right about 0.00004" for the tolerances.

According to Wikipedia, that puts the bearing grade at about 25, or maybe a little better.

https://en.wikipedia.org/wiki/Ball_%28bearing%29

Still a little inconclusive as there's several dimensions listed against any one grade, but I'll certainly agree that it does confirm that they're (were) more than good enough to do the job!

That's not quite what it shows. That Campy document claims their bearing balls are ground to .001 mm tolerances. But ball grades are based on inch tolerance numbers and 0.001 mm = 0.00004". The document it doesn't specify if the tolerance is for diameter or sphericity but a sphericity tolerance of 0.00004" is between Grade 50 (sphericity tolerances of 0.00005") and Grade 25 (sphericity tolerance of 0.000025") and if it's a diameter tolerance it puts their balls at about Grade 10 (diameter tolerance of 0.0005" which is the same for Grade 10 and Grade 5).

Agonizing over numbers aside, yes indeed Campy's bearing balls are more than good enough but so are Shimano's.

You didn't by any chance work on the mars orbiter a while back?

As the others have said, you made an error in translating metric to inch and (according to the literature) it seems that Campy does in fact use grade 25 (or possibly 10) balls.

Whew, I'm glad we got that straightened up.

BTW- while we're discussing balls, I remind you that lot tolerance is much tighter than overall tolerance, so it's important not to mix lots (lots of debate about that) because if you mix 2 lots of grade 25 balls you made one lot of grade 100. In practice one smaller ball in a bearing isn't a big deal, but on larger one is more serious. So for those who pay for grade 25, remember to discard the end of a lot before opening the new one.

Campy used to advertize grade 25 bearings at the same time I bought some grade 24 balls at a local bearing house in the united states at around 5 cents each. Bearing manufactures are constantly making small improvements they don't advertize. There used to be an exhibit in the Chicago museum that bounced ball bearings off two inclined planes to show how accurately they were made. Ceramic ball makers advertize they can be used without lubrication this is nice if you don't like to tear down hubs.

Excellent! Quite right - and I have been in the wrong for so many years. I really appreciate your pointing this out, but I am afraid I will find it hard to resist correcting others.

so we now have 2, it's a groundswell!!!!!

I guess I did botch it didn't I?

As always, I'll admit when screw up. It's happened before, it'll happen again.

But it's not like you made a multi-million dollar satellite crash into Mars. If rocket scientists can make a simple metric/imperial mistake, I guess we're all entitled.