Are "satin" (non-shiny) wheel bearings okay?

Question

I have inspected all four real wheel bearings. On one of them, both the rollers and outer race have a "seemingly perfect" mirror-like finish.

The other three have a "flat-like-paint" or "satin" appearance to them, both in the rolling area of the outer races, and also on the roller bearing surfaces. They are not pitted or discolored. In fact, I went through the entire Timken guide to failing bearings, and nothing matched my bearings. Well, except the original exemplar of what a good bearing should look like, which I note was flat and not chrome-shiny.

All of them roll exactly as you'd expect, with no bench indication of a problem. I have since repacked them and run them 100 miles with no indication of trouble.

Is it possible my 3 bearings are good and the shiny one has a defect?

Reasons I think there might be a problem:

• 250,000 miles on these bearings, but it's a very light car
• Car ran for tens of thousands of miles too loose, and had a tiny amount of play. This was due to using the old GM preload method* rather than the shop manual method **. The difference is considerable.
• At one point on rural western freeways (80 mph) the right rear (both bearings satin) started growling. Slowing to 45 made it stop. This happened for a few miles then went away on its own and did not return in 1500 more miles of 80 mph driving.
• Physical inspection of the right bearing seat showed slight discoloration, like a bearing spinning on the seat (i.e. Stalled bearing). No galling or anything a finger could feel, and no burned or stinky grease there. I didn't even mic it, it was so minor.
• Old grease in the right inner bearing was brown/gray and smelled a little burnt.

Can this be continued in service? It'll have plenty more high speed, long cruise rural driving.

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Sorry, I don't have any means to post a photo of sufficient clarity (I don't have a macro-lens camera, and my phone is way too stupid to focus on the right thing inside a part like that). Also, it's been repacked and buttoned up again, and I don't plan to reopen it without a good reason.

* seat with a couple foot-pounds, back off, then finger tight, then tighten to the next castle slot (e.g. 10-60 degrees)

** seat by torquing to 20 ft.lb., back off, then tighten until when bearing drag adds 8-18 inch-pounds of resistance to wheel rotation. Castle provided every 10 degrees.

Answer 1

There are four basic things I would look for when looking at bearings outside of the vehicle. In order to really inspect them, they should be fully cleaned so no grease remains. (NOTE: Some sealed bearings will you'll not be able to clean ... so do your best.)

1. Play - Do they seem to be relatively tight, as in don't rattle too much? Do all of the bearings seem to be of the same tightness if rattled? In this aspect, you are basically playing with the bearings to ensure none of the bearings fall out or appear to want to fall out. These things would be caused by excess wear.
2. Noise or vibration - When you rotate the races separately, does the bearing flow smoothly? Do you hear any noise? Are there any rough spots, which might indicate some of the bearings might have flat spots in them? In this aspect, you're looking at whether any of the bearings have seen a hard life. Since it's a wheel bearing, things like hitting a curb with the wheel might cause these conditions.
3. Color - Are any of the components blue? Blue is a sign the bearing has seen excess heat, which means it's already had a hard life. If it's blue, it's lost the temper in the metal and could fail at any time. If your bearing is shiny, this wouldn't indicate anything to me, unless one of the other things here was true.
4. Complete? - Does the bearing look complete, as in, does it have all of the rollers or ball bearings? Does it look like it's missing something? Is the retainer still in place and complete? In this aspect, if it looks wrong, it probably is wrong.

In any of these cases, you should change out the bearings for a new set. With what you are describing, I don't think I'd be too worried about the shiny bearing unless you see one of the problems above. It could just be from a separate batch of bearings, or possibly from a different manufacturer. Vehicle manufacturers use different suppliers to provide these types of assembly products to ensure a steady stream of parts during the manufacturing process. It could just be the single bearing which is a different color might not be because it's worn out, but rather might have a slightly different manufacturing process. This doesn't mean it's bad ... just means it's different.

If the bearing race were to turn in it's bore, you'll almost always see galling on the holding part (ie: hub or spindle) and not the bearing itself (unless things get really bad). The reason for this is, the bearing races are heat treated to be very hard. A lot harder than the surrounding metal of the holding part. If there is any galling on these parts, you've got an issue for sure (though it seems like you already know this).

If the bearings are not closed bearings, clean the bearings thoroughly and repack with clean grease. Correctly repacking the bearings regularly is just proper maintenance, so you'll have no issues. Some inner bearings are held there by seals, so if you pull it lose to get at the bearing, you'll need to replace it.

You'll ultimately need to decide if the bearings can be reused, but from the sounds of it, they should be in good shape. As Moab stated in the comments, don't over tighten the wheel bearings when re-installing. This is a sure way to destroy them in short order ... especially older ones.

Answer 2

Adjusting bearing preload is a developed feel. As to the bearings and races. A dull finish on either bearing or race, they need replaced. After 200K I would without hesitation replace them. You can put an old bearing on a new race, never a new bearing on an old race. Packing the bearing does not mean just smearing grease around the bearing and stuffing it in the hub. The palm scrape method works good, a pressure packer is better. You can get one at a parts store for a few buck. Put a rag over mine and step on it to mash the grease in. I use Valvoline high temp, the red stuff, never had a problem with it.