Wheel bearings are integral in allowing a wheel to distribute weight and reducing the friction of spinning. Bearings are packed in grease as a lubricant and situated inside a hug. Wear, dirt, water and other debris can reduce the effectiveness of the bearings, causing them to break down. Replacing the seals and repacking them are important maintenance steps to avoid a costly repair.
Unscrew the lug bolts on the wheel with the lug wrench, and slide off the wheel.
Pry gently on the grease cap using a flat-head screwdriver to remove it. Spin the wheel as you pry around the edges, to lift the cap until it comes off.
Remove the cotter pin that holds the castle nut in place. There may be a cage or lock washer instead of a cotter pin, depending on the wheel arrangement. Pry up a nut cage or lock washer with the screwdriver. For a cotter pin, simply bend it straight and slide it out.
Loosen the castle nut with a ratchet wrench, and remove it. For wheels with attached breaks, loosen the nut on the caliper and slide them off the hub first. Slide the entire hub off the spindle.
Pull the outer bearing and spindle washer out of the center of the hub. Turn the hub over, and set it on two small blocks so that the center of the hub has an open area below it. Use the small block of wood and a hammer to tap the center bearing and seal out. The wood will distribute the force of the hammer without nicking the metal. You can also use the screwdriver to puncture the seal and pry out the assembly, since they are being replaced.
Set aside the bearings on a paper towel. It is a good idea to clean them and repack with grease while you have the assembly apart.
Clean the inside of the hub and the spindle. Grease the race, which is the inside collar of the wheel hub. Turn the wheel over and slide the inner bearings into the hub, then place the seal in on top. Tap the seal gently to seat it. Grease the seal. Slide the wheel back on the hub.
Slip the outer bearings and outer seal onto the spindle and into the hub. Slide the lock washer onto the spindle if one was used. Place the castle nut in place back on the hub and tighten. Rock the hub to make sure of a tight fit, then tighten the castle nut again. If a cotter pin is used to secure the nut, replace it now, then bend it to lock it. Replace the wheel.
