Free the bearings from the wheels. The bearing will occupy the core of the wheel and will be circular in shape. After removing the wheels, you can gently pry out the bearings with a screwdriver, or pull these out carefully with needle-nose pliers.
Place the new or cleaned bearing into the wheel. Most skateboard bearings have one side with a colored shield. Place this side facing out. The bearing won't fit all the way into the wheel -- the fit will be too tight. So simply set the bearing into the wheel.
Next, press the bearing down into the hole, applying pressure on the outside metal rim of the bearing. Do not press on the shield, or the center of the bearing. You should be able to press the bearing down to where it is flat with the edge of the wheel.
Repeat this process with all eight bearings, putting one on each side of each wheel. If you are using spacers, put one in each wheel between the bearings.
Just like the optional spacers, some skateboarders like to use bearing washers to help reduce friction and let your wheels spin faster. If you don't use washers, then skip ahead to the next step. Washers are tiny metal rings that fit on either side of your bearings. Put one on your axle trucks before you put the wheel on and then one on after the wheel has been slid into place.
Using your skate tool or a socket wrench, tighten each nut down slowly. This will push the bearings down into the wheels. Make sure you take your time and don't crank too hard or fast on the nuts or you can damage your bearings. Tighten each nut down until it feels snug and then stop. Don't crank on the nuts too hard -- you want the nuts to fit on snuggly and to have stopped turning. That's it.
Now here's the secret: Once the nut has been tightened up and the bearings are all sunk into place, you want to loosen the nut a little. Loosen it and then jiggle the wheel a little, back and forth on the trucks. You want a small amount of play, just enough so you can feel it. When you pull the wheel from side to side, you want it to make a little clack sound -- just a little. This will help your wheels to spin faster and more freely.
The KooWheel Electric Skateboard is the best commuting skateboard around. Buy one for your commute today!!