Ball Bearings?
 

When serving my hubs I often replace the bearings every few years or so. Since I work at a bike shop it is easy to do during quiet times.
Wondering if anyone has noticed a difference using grade 25 ball bearings vs. Just run of the mill?

Grade 25 balls are affordable at no great premium over lower grades, so that's what I use. I don't see any point to justify the premium of going to ceramic balls, though.

I can't say that I have ever felt any in hand differences between well serviced and adjusted hubs of the same grade but having different grade balls in them. My opinion is that a bit of grime or a slightly off preload adjustment will result in more negative effect that "lowering" a ball's grade will. Andy.

grade 25 balls are only marginally smoother than decent, well made, grade 100 balls.
the grading refers to the maximum allowed defects in the surfaces, in both roundness and surface finish.
the surfaces of the cups and cones is usually WAY rougher than the bearing balls.
putting gr. 25 in a cheap, rough hub assembly, with pits and scratches in them, just ruins the bearing balls.

most bearing balls sold for bicycles are Gr.25...
i buy them 1000 at a time, and for less than what some ripoffs charge for 10 of them.

gr. 10 is so close to gr. 25 that without special equipment, you could never notice the difference in finish.

avoid stainless steel bearings. They are softer than the standard high chrome steel bearings, and deform easily at the contact points. SS material has a bad habit of tearing when ground or cut, so the surface finishes suffer because of that factor.

in bulk.. the gr. 25 chrome bearing balls cost about 1.2 cents, US, each, shipped to your door.

Since I ride Campagnolo hubs, cranks, pedals, etc. I'm already running grade 10 bearings, so grade 25 would be a step down. That said, proper maintenance is a more significant factor.

Don't you want the ball bearing to be soft? The ball bearings can be easily replaced. The bearing race cannot. You want the balls to take all the wear instead of the race.

nope.
ideally, they should be equally hardened.

SS bearing balls are terrible, and only intended for exposed/corrosive situations, and they need frequent replacement intervals..

fortunately, normal use on bicycles never really test the limits of the bearings' strength, as long as there was no major defects in them.
gravel bikes used on gravel(High Vibration. a series of rapid impacts), and insane dirt jumpers approach the limits.

once a bearing distorts, it takes time to resume it's former shape... that time lag then overloads or under-loads the next contact point... the oscillations increase idf the resonant frequency is maintained...
think of the ripples created after a pot hole in a road... they're created by rebound movements.
the rippled red cinder roads outside of Bend, and other rippled gravel roads... the ripples aren't felt much once the car reaches 60mph or so... the tires no longer enter the valleys of the ripples.
bike bearings never reach that escape velocity... they drop into every deformation they can find.
deformation generates heat too... heat buildup is never good in a bearing set at room temperature.

Grade 25 from BC Precision.