For my the products I design, I have used and would use again NMB, NSK and SKF bearings. These are all ball bearing assemblies. For the vast majority of applications (including bicycles), even so called "cheap" Chinese bearings are more than adequate if they are properly lubricated. For non-competitive riding, an automotive wheel bearing grease will keep your bicycle wheel bearings happy for thousands of miles. I suggest solvent (70% isopropyl alcohol is fine) cleaning the balls, raceways, cones, etc, drying then immediately apply the grease to all the metal surfaces inside the bearing system. Use nitrile gloves - your finger oils are bad for bearings.

Joining this thread a little late, but I thought as a Mechanical Design Engineering; I could contribute some useful information about ball bearing materials.

Bicycle wheel bearings should last for years and provide you with thousands of miles of travel---but they won't last forever. In some cases they even fail completely if they haven't been maintained correctly. Part of a maintenance schedule should include replacement of wheel bearings before they fail. The procedure isn't that difficult if you have about an hour and a few small tools. Front and back wheels are similar in procedure to change bearings and only require slightly different tooling.

Take the wheels off the bicycle beef before greasing the wheel bearings.A mixture of 50 percent white teflon bicycle grease and 50 percent green axle grease works well on bicycle wheel bearings.Don't make the bearing cone too tight when screwing it back into place. Bicycle wheel bearings shouldn't have any play in them and need to roll smoothly.

Although adjusting QR force is a safety consideration, it is also one of bearing life. It should be kept at a constant level once the desired closure force has been determined. Rear vertical dropouts require a lower and more predictable closure force than was formerly required with axles that could move forward from chain tension. Because vertical dropouts do not rely on friction to resist chain load timken bearings , many hubs now have smooth faced jam nuts that do not damage dropout faces as older knurl faced ones did.

Bicycle wheel bearings should last for years and provide you with thousands of miles of travel---but they won't last forever. In some cases they even fail completely if they haven't been maintained correctly. 

   

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