Wheel bearings are built to last a long time, so when one fails early there is usually a reason. Knowing the causes helps you prevent a repeat. Here is what causes wheel bearings to fail.
Water and dirt intrusion
A bearing's biggest enemy is contamination - once the seal lets water, salt, or grit in, the grease breaks down and the bearing wears fast; see heavy-vehicle wear. Driving through deep water or pressure-washing right at the hub can force water past the seal.
Impacts and potholes
Hard hits from potholes, curbs, or accidents can dent or brinell the bearing races, leading to noise and early failure. Bearings do not like sudden shock loads.
Wrong torque or bad install
Over- or under-torquing the axle nut or hub bolts sets the wrong preload and kills a new bearing quickly; see why hub torque matters. Not seating the hub flat on a rusty knuckle causes runout and uneven load too.
Heavy loads and modifications
Constant heavy loads, towing, or oversized wheels and wide tires add stress that shortens bearing life. Keep loads within rating and torque everything correctly; see how to check a bearing. Keep the brakes fresh with quality pads and hardware.