Another ball bearing Q:

Michael said:

I didn't remember when I last replaced the front bearings on one of my bikes,
and when I looked in the maint. notebook I discovered that the last entry for
that axle on that bike was dated January 2004. Could it really have been so
long ago? I didn't think so. Decided to have a look at the bearings under
magnification, just for grins. I was surprised to see that the surface of every
bearing was ... mottled, for want of a better word. Not pitted or burned, just
not homogeneously shiny and smooth-looking as I thought it should be. Try to
imagine what continents and oceans of a steel Earth might look like from the
moon: mirror-like oceans; light gray continents with ripple-like borders.

Are these bearings corroded? Worn? Heat damaged? Typical of high quality
bearings in good condition? Typical of low quality bearings in good condition?

Your bearings are showing a normal wear pattern. Unless they show pits
they're perfectly usable but most people would replace them since
they're only a buck for the lot.

Michael said:

I didn't remember when I last replaced the front bearings on one of my bikes,
and when I looked in the maint. notebook I discovered that the last entry for
that axle on that bike was dated January 2004. Could it really have been so
long ago?

Sure! Lots of people don't break open their front hubs any more often
than every two or three years; if the bike's not ridden a lot, it
could be longer without trouble, if decent grease was used and the
sealing was effective. I go by three indicators. If the bike has
been out in the rain, then at least annual inspection and repacking is
warranted IME, and the balls usually show some discoloration. If the
bike is used but new to me, I inspect and repack the hubs just to
establish a zero-time base mark. And every second or third chain, I
repack the hubs. Discolored, pitted or otherwise non-shiny balls get
replaced whenever the hub is apart; that's why I buy the balls in 100
packs.

Quoted message said:

I didn't think so. Decided to have a look at the bearings under
magnification, just for grins. I was surprised to see that the surface of every
bearing was ... mottled, for want of a better word. Not pitted or burned, just
not homogeneously shiny and smooth-looking as I thought it should be. Try to
imagine what continents and oceans of a steel Earth might look like from the
moon: mirror-like oceans; light gray continents with ripple-like borders.

Are these bearings corroded?

That's what it sounds like.

Quoted message said:

Worn?

If not now, then soon, once corrosion has taken place.

Quoted message said:

Heat damaged?

Unlikely. A front hub that was hot enough to discolor the balls would
have attracted your attention via that time-honored phenomenon, the
release of the Magic Smoke that occurs when things get seriously
overheated.

Quoted message said:

Typical of high quality
bearings in good condition? Typical of low quality bearings in good condition?

Typical of bearings that perhaps could have had a relube sooner.

Remember, most greases will form an emulsion with water, and the
emulsion will corrode the bearings.
--
Typoes are a feature, not a bug.
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Michael said:

I didn't remember when I last replaced the front bearings on one of my bikes,
and when I looked in the maint. notebook I discovered that the last entry for
that axle on that bike was dated January 2004. Could it really have been so
long ago? I didn't think so. Decided to have a look at the bearings under
magnification, just for grins. I was surprised to see that the surface of every
bearing was ... mottled, for want of a better word. Not pitted or burned, just
not homogeneously shiny and smooth-looking as I thought it should be. Try to
imagine what continents and oceans of a steel Earth might look like from the
moon: mirror-like oceans; light gray continents with ripple-like borders.

Are these bearings corroded? Worn? Heat damaged? Typical of high quality
bearings in good condition? Typical of low quality bearings in good condition?

--
Michael

Worn and worn out. When they become not round, they then pit cones and
races...I replace all my bearing balls once per year.