Let’s Talk About Wheel Bearings

by Don Elliott on July 9, 2012

This column is devoted to finding used car values at all stages of car ownership; the car buying process, car auction sales, used car pricing, maintenance, insurance and financing. Often, it is the little things that add the most value.

Recently, a friend called to ask if her SUV really needed a new wheel bearing and…what was a wheel bearing anyway?

Wheel bearings have two functions on a vehicle. First, they allow the wheels to move freely around the axle with a minimum amount of friction. Second, they support the weight of the car. The wheel bearings are located within the hub of the wheel, at the center area between where the lug nuts hold the wheel onto the hub.

There are four main wheel bearings, one at the end of each axle. Most wheel bearings on newer cars are sealed, with the lubricated bearings enclosed to protect the moving parts from dirt and moisture. Amazingly, wheel bearings are designed to last the life of the car, generally considered 150,000 miles, without maintenance.

On older cars, it is possible to replace the seals when they fail and to add fresh grease. Vehicles with sealed wheel bearings require that the entire hub be replaced.

Diagnosing a failing wheel bearing is not difficult. A smoothly operating bearing makes virtually no noise. As the bearing becomes contaminated with dirt or water, the intense pressures within the bearing assembly cause the bearings to wear out-of-round or grind down creating a vibration. As the wheel bearing deteriorates the whirring noise will increase. Tire noise and wheel bearing noise often sound the same at first, but the bearing noise will increase over time sounding more like screeching as it gets worse.

One way to check which wheel bearing is going bad, with the windows rolled down, sway the car from right to left. The whirring or vibrating noise will get louder as more weight is applied to the bad wheel bearing during the swaying maneuver. Unfortunately, once a wheel bearing starts to go bad, it will eventually fail. When a wheel bearing fails, the hub and the axle seize together stopping that wheel from turning. At 70 miles per hour, the result can be devastating.

Considering the critical job that wheel bearings have towards the performance of the car, it is unusual for wheel bearings to go bad with under 100,000 miles on the car. Auto technicians are trained to check the wheel bearings on higher mileage cars when those cars come in for tire, brake or suspension service. When purchasing a vehicle from an auto auction, take advantage of their post-sale inspections that includes the mechanical and frame inspection of vehicles. The technician will check for any movement in the hub on the axle, a sure sign that the bearing is wearing down.

Replacing the wheel bearing hub assembly before it fails is not particularly expensive. The hub assembly itself costs a few hundred dollars, with an aftermarket part costing about 25% less than an OEM part. Labor varies significantly depending on the vehicle. A typical hub assembly replacement is $350-450, maybe less. Because the wheel bearing fails gradually, there is usually some time for a second opinion or to raise the money for the repair.

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