These cars have tapered bearings like the old days, pack with grease - pack some into hub cavity and adjust the nut, its doable by hand if you have the knack for it - The benz way of using the dial gauge was to make this task repeatable by any person.

If you hear a rumble replace the bearings immediately - you have an incredibly narrow window of time to save the spindle.

Usually bearing failures are seen more in the dead of winters (even a search here will somewhat show that) - a removal and repack with fresh grease is not too much cost either, a container of wheel bearing grease costs 5 dollars, the seal is expensive on the later cars like W211 but way cheaper than a new spindle.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)