Wheel bearings again!

Leaf-Peeper wrote:

byways wrote:
... I KNOW the axles were properly lubricated on both occasions (prior to failure). This recent bearing/axle has less than 3,000 miles on it, and is less than 1 year old.

What causes this?

In a previous and somewhat unrewarding career, I used replace damaged axle housing spindles on over the road trucks, tractors and trailers. The bearing failures in these instances were so severe, the spindle would end up being heavily damaged. Sometimes they got so hot, they'd catch on fire.

Based on my experience, if the bearings were adequately lubricated, there's a high probability the failure could have been caused by the spindle nut being installed too tightly.

My guess is that in about 75% of the failures I saw, the truck or trailer had recently had the brakes serviced (which required the removal of bearings). I believe in most instances the bearings were probably adequately lubricated, but the failures likely occurred because spindle nut was installed too tight, which resulted in insufficient bearing clearance.

I recall an instance where a concrete pumping truck (tandem drive axles) had gotten just a few miles from the service shop after having it's brakes serviced, it had ruined a drive axle housing spindle, for which the road service guy chained-up so it could be driven back to the shop. Before the truck could make it back those few miles to the shop, the other spindle on the same side of the had also failed. Turns out there were two guys involved doing the brake service... one worked the right side of the truck, another on the left side of the truck. Inspection of the spindles on the opposite side of the truck showed no signs of wear or damage. One guy seemed to know what he was doing, the other guy apparently did not.

In a snapshot, here's how I tighten our trailer's spindle nuts (your results may vary):
I'll rotate the hub/drum when tightening the spindle nut to ensure the bearings are able to seat themselves (often done using a pair of channel-locks). After it's snug and without any rotation of the hub, I'll loosen the nut and then retighten it just finger tight. In most instances, the nut will have to be backed off a bit further to allow installation of the cotter pin. After assembly and the wheel/tire is back on, I do a simple lift test... momentarily lift up the bottom/outside area of the tire to be sure there is some radial play detectable.