bearing failure 400E

[peterhardie]

My wife's 400E recently experienced right front wheel bearing failure. SHe started feeling some wobble while driving on the highway, pulled over, and smoke was coming from the wheel, which was also covered in grease.

When she got it to my tech, he said the heat had actually fused the bearing to the spindle. Being the good friend that he is, he proceeded to read me the riot act about how I could ignore the noise the bearing was making before it failed. Truth is, my wife has a great ear for car sounds, and good sense for when things ain't right, and neither she or I heard or felt any giveaway signs. I replaced those bearings less than two years ago, and on a recent maintenance I retightened the bearings on both sides.

My question is what might have caused the failure and why would we not have had any warning? I have two theories.

One is that I overtightened the bearing. The second is that I may have mixed different types of grease, which I have heard will sometimes interact with the result of thinning and decreased effectiveness.

Neither of those theories feel right to me. Any ideas? The wife REALLY does not like breaking down on the highway.