I am sure it's not the bearings.

I have had the truck since it was new in 1995. It has been doing this for as long as I can remember. As long as it's warmer then 10F there is no problem. Once or twice a year we get a cold snap and it happens.

When I rebuilt the brakes, the bearings were fine at 120000 miles. I rolled new grease into them and put things back together. The torque on the bearings was checked a few miles later.

If it were the bearings the sound would be constant but, the sound builds and falls with rotation and is linked to the speed of the wheels not the engine RPM.