Originally Posted by rykoala
Well, mrhedges was correct. Missing balls in the hub. The hub *came* with only 9 per side, and it takes 10. I scavenged two ball bearings from another hub that is in the middle of being rebuilt, and put those in. Now, its as smooth as can be expected. Thanks for the help everyone!
I've heard that it's best to avoid mixing and matching ball bearings from different lots - so that they're all about the same size and wearing evenly. It may not matter as much with grade 25 balls as with grade 200 ones.