1991 Mercedes-Benz 420SEL Wheel Bearing Replacement Cost

A wheel bearing is part of the front and rear wheel hubs. In the front, the hub connects the wheel to the suspension's steering knuckle. The wheel connects to the hub, and the hub spins smoothly inside the wheel bearing. This allows the weight of the vehicle to rest on the hub as it spins while maintaining as little surface contact as possible. The wheel bearing is lubricated with grease in order to further reduce friction. Most vehicles feature sealed wheel bearings that encapsulate the ball bearings and the lubricant.

Some of the more common signs of wheel bearing problems include:

Groaning, rumbling or grinding noises coming from the wheels or tires — these sounds may also get louder when you make a turn. 

The car handles more loosely.

Vibrations and wobbling through the steering wheel.

The car pulls to one side as you drive. This may occur at random. 

The tires wear unevenly.

If the above symptoms are ignored, more serious consequences can happen:

One of the wheels starts smoking.

A wheel comes off the vehicle.

Yes, but not for long. As the wear increases, so do the chances of damage occurring to other parts of the suspension. If you suspect that a wheel bearing is beginning to wear, have a technician evaluate the problem as soon as possible. A vehicle with a significantly worn wheel bearing shouldn't be driven. If the wheel bearing fails completely, it's possible for the wheel to come off the vehicle and cause a wreck.

Most vehicles have sealed bearings that do not require maintenance. Sealed bearings can last 100,000 miles or more, and will need to be replaced once they go bad. Vehicles with traditional, tapered wheel bearings should have them serviced every 25,000 to 30,000 miles — replacement may not be necessary as long as they're maintained.  

To diagnose whether a wheel bearing is going bad, a technician will typically take the vehicle for a test drive to verify where the sound is coming from and determine which wheel bearing is the culprit. In the shop, the technician might lift the vehicle, rotate the wheel, and listen for sounds from the wheel hub. The technician will also test the wheel for excessive play by holding the tire on each side and rocking it back and forth. If there is play in the wheel and the steering and other suspension components are in good condition, the bearing has likely worn out.

To replace a wheel bearing, a technician will need put the car on a lift, remove the wheel and tire, and remove the brake caliper and rotor. On some vehicles, the wheel hub and bearing are simply unbolted from the steering knuckle and can replaced as a unit. On other vehicles, though, the hub and bearing are pressed together into the knuckle and need to be removed with special tools. In these cases, a hydraulic press must be used to insert the new hub.

The front wheel bearing is an essential component of the vehicle suspension. As a wheel bearing wears out, more friction is created — and more damage occurs. On most vehicles, the wheel bearing requires special equipment to be serviced. If a bearing is installed improperly, it may fail early.

Some vehicles with sealed front wheel bearings can be serviced at home. If the wheel hub and bearing are simply bolted to the knuckle and can be replaced as a unit, an intermediate DIYer with experience removing brake or suspension parts can do it. But many cars require that a technician remove hubs and bearings that are pressed into the knuckle. These components are difficult to disassemble, and reassembly requires a hydraulic press. In such cases, wheel bearing replacement is best left to a professional technician.