Originally Posted by
hoyc
Just a note, that the hub were already grinding when I bought these wheels used 4 years ago. I just didn't get around to servicing them until now. The front hub spins smoothly.
First of all it's definitely the bearings, so replacement is necessary. However the problem may also be the (prior) owner. Radial contact bearings like these are not designed to tolerate side loads, and in this respect are very different from the angular contact design of basic bike cup/cone bearings.
see sketch here
Many mechanics, home, and pro both are unaware of the difference and it's implications and adjust radial bearings with the same preload as they are used to using. That has the balls running on the edges of the track which rapidly disintegrates. These will run fine in your hand, but grind in the hub.
Keep this in mind when you install the new bearings, and adjust them to take out all bue the last vestige of axial play, do not preload them.