[Beav]

Pretty much a little bit of everything. The bearing is undersized for the application, IMHO. The grease that the bearings are shipped with....hmmm...that's a fishy story. I'm not saying that the 'shipping' grease is good, but typically a bearing is coated with cosmolene (sp? a thick, yucky substance for rust prevention) or it's shipped dry or packed with the proper lube.

Next is the actual pressing - I've witnessed many guys use an air hammer to drive hub bearings in and out. O.K., I've done it a time or two myself. However if the hammer bit slips and whacks the machined surface it's hasta la vista, bearing.

Torquing things down properly is also a must. Here again a lot of pros will just whack it with the impact wrench and call it done. Problem is that most of them don't realize how much torque they've just applied. If they just pull the trigger down and hold it until the first smack of the gun that's about 90-100 lbs./ft. Most of them will rata-tat-tat bolts to the 150-200 lb./ft. region.