Some sealed bearings can be serviced and some cannot. Most hubs, bottom brackets, headsets and pedals have sealed bearings in the modern age of bicycles. Some of these bearings have rubber seals that can be removed and serviced to prolong life and save money. The above video shows the basic steps for taking care of these bearings once they are removed from the bike. Getting them out of the bike and ready for servicing is another video for another day.