Originally Posted by
HillRider
There are indeed stainless steel bearing balls available (usually 440C) but they are a specialty item used only where their corrosion resistance is of value. I don't know of any bicycle component that uses them either OEM or as replacements.
Bike Tools etc. carries a (very) small selection of loose balls made from 440C stainless steel.
At least on
one specification sheet, 440C ball bearings have a lower value on the Rockwell scale than normal chromium steel ball bearings, meaning the stainless steel ball bearings are softer. Whether that difference is significant for bicycle use, I don't know.
Originally Posted by
HillRider
Campy claims their bearing sets are individually matched and therefore charges much more for their name on them. But they aren't stainless steel and, if there is any performance benefit to the extra "matching", no one has really demonstrated it.
I see/hear this alleged Campagnolo claim many times, but I've never seen a Campagnolo rep or ad material state that. Nevertheless, the numeric grade given to ball bearing grade specification refers only to the sphericity and lot diameter variation; the overall ball diameter tolerance is also specified but is a much larger number.
For example, Grade 25 ball bearings are constraint to within 0.000025" sphericity and lot diameter variation. However, the overall ball diameter tolerance is 0.0001", and this is 2 orders of magnitude larger. So, at least on paper, it would seem prudent to "match" loose balls to the same lot to gain 2 orders of magnitude of uniformity. However, I don't know whether that has any meaningful impact to smoothness or durability. Sounds good though!
