A vehicle's wheel hub bearing fits inside the hub and allows the tire and wheel to spin easily on the axle without damaging it. It also works as part of an assembly that holds the hub, tire, and wheel on the axle. If one of these bearings becomes worn or damaged, it can allow the wheel and tire to come off while the vehicle is in operation.
Block the unaffected tires to prevent the vehicle from rolling when you raise it to work on the bearing. Jack up the corner of the vehicle where the hub bearing needs to be replaced. Position a screwdriver with the point at the place where the dust cover and the hub meet at the center of the car wheel. Make a couple light taps on the screwdriver with a hammer to loosen the dust cover so you can pull it off.
Straighten the ends of the Cotter key or pin with pliers. Grip the folded end and pull it out of the hole and the nut. The Cotter key or pin is a folder piece of soft thick wire, located under the dust cover, that is inserted through a hole in the end of the axle and slots on the nut. It keeps the nut from unscrewing from the axle.
Record how much of the axle threads are exposed beyond the nut. This is the approximate spot that you will want to tighten the nut back to when it is replaced later. Use the pliers or a wrench to unscrew the nut from the axle. It is usually easy to do.
Grip the outer edges of the tire and work it back and forth to make the bearing pop out. Slide the bearing off the axle. Remove the tire and wheel with the hub and set them aside.
Examine the axle for any signs of wear or damage. These will appear as cracks or grooves cut into the axle. If the axle looks good, coat with axle grease before replacing the tire and wheel. Lift the hub, tire, and wheel back into place and slide it onto the axle.
Apply axle grease liberally to the new bearing. Use your fingers and work the grease into the bearing so that all of the roller bearings are well coated. Slide the bearing onto the axle with the tapered end facing the car. Ease into place until it is flush with the outside of the hub.
Screw the nut back onto the axle. Use a wrench to tighten it to the point that it was resting before you removed it. Turn it until you can slide the Cotter key back through the slots on the nut and the hole in the axle. Bend the ends of the Cotter key to secure the nut. Replace the dust cap. Lower the car and remove the blocks.
