Once greased up and put back into place, wheel bearings need to be tightened in a very specific way. If this is not done properly, they can become too tight and that will cause excessive wear to the bearing itself, ultimately causing it to fail. However, if the bearing is not tightened enough, the bearing will loosen itself up and the entire wheel may fall off. Needless to say, tightening a wheel bearing has to be done carefully and precisely.
Tighten the bearing for the first time. Thread the wheel bearing nut on until it is hand tight. Take your wrench and place it over the wheel bearing nut. Tighten the nut until it is firm and cannot be tightened anymore.
Loosen the nut back to where you can turn it with your fingers. You will need to use the wrench and your fingers.
Tighten the nut to where it is tightened firm once again. Use the wrench to make it as tight as possible.
Loosen the nut to where you can once again turn it with your fingers. We are doing this to seat the bearing on the axle and to also remove any air bubbles from the grease inside the bearing. You will do this five more times.
Tighten the nut so that it is verifiably firm, but not overly tight. To check this, look at the notches on the nut. The nut itself will have notches in it on the ends. You will also see on the axle that there will be a hole going through it. When tightened for the final time correctly, one of those notches on the nut will line up exactly with that hole going through the axle.
Fix the nut in place with your cotter pin. Take your cotter pin and push it through the hole in the axle. It will also butt up against the notch and form a positive stop point so that the nut can never unthread itself. Using your small hammer, pound the ends of the cotter pin over so that it looks like a pare clip. This will lock the pin into place so that it won't fall out.
Use your small hammer to pound the ends of the cotter pin over so that it looks like a pare clip. This will lock the pin into place so that it won't fall out.