The majority of wheel bearings used in late model vehicles are a component in a hub. Hubs, which not only carry the wheel bearing but also the sensor for the ABS system, are used on front wheel drive and rear wheel drive cars and light trucks. The hub uses a sealed bearing; this bearing does not require any periodic attention as did the bearings in older cars. It is however, always a good idea to have your automotive technician inspect the condition of the hub assembly when the wheel is off.
A typical hub contains two bearings, inner and outer; they can be tapered roller or ball. Tapered roller bearings are perhaps the better alternative, as the design is such that they can carry vertical as well as sideway loads and can stand extreme shock such as that introduced into the vehicle when it hits a deep pothole.
The construction of double row ball bearings and tapered roller bearings is similar inasmuch as the rolling element is held in place by a cage. Ball bearings do have their advantages; they are less costly to manufacture and as there is less friction with a ball bearing, fuel economy is usually better. The problem with ball bearings is their inability to take heavy lateral loads, they don’t last as long as tapered bearings, especially if the vehicle makes hard corners such as a racing car.
Wheel bearings, regardless of the type are made using high quality, high spec steel. The inner and outer races and the rolling element; ball or roller, are heat-treated. The hardened surface adds considerably to the bearings wear resistance. Most high quality wheel bearings in service today can comfortably handle 200 thousand miles or more before they need to be replaced.
Even the best wheel bearings fail:
Any wheel bearing can fail; failure will occur prematurely if water, dust and road salt get past the bearing seals. The result of bearing contamination is corrosion of the steel components which increases wear, which eventually leads to failure.
If you begin to notice an odd noise; chirping, squealing, humming, etc. coming from one of the wheels you can almost be sure the wheel bearing is failing. If the wheel shakes even the slightest amount you must get the hub assembly with bearing replaced as soon as possible as the car is really not safe to drive.