Sealed bicycle hub bearings are becoming more and more common on modern bicycles. Because of their maintenance-free design, long life and smooth rotation, it could be said that they are better than traditional ball-bearing-and-race designs in almost every way. The downside to sealed bearings is that when they do go bad or need repair, they can be difficult to remove from the hub. Learn how to take out your sealed bearings for replacement or maintenance and keep your modern bicycle hubs spinning smoothly.
Remove the wheel from your bike. On older bikes, loosen the 15mm axle nuts with a wrench. On track bikes, loosen the axle bolts with a 6mm hex wrench. On modern road and mountain bikes, simply loosen the quick-release lever. Pull out the wheel from the dropouts and away from the frame.
Remove the outer nuts on the axle using a pair of cone wrenches. Hold the inner cone in place with one cone wrench and twist the outer nut counterclockwise with the other cone wrench. Repeat this procedure for both sides of the axle. Note that on track-style hubs, you only need two 8mm hex wrenches to remove both nuts from the hub.
Remove the first sealed bearing by hitting the end of the axle with a hammer. It may take a lot of force before the axle starts to move, but eventually you will force the axle and the first bearing out of the hub. Set the bearing aside.
Flip the wheel over and insert the axle into the centre of the hub against the second bearing. Repeat the hammering procedure once more to pop this bearing out of the hub as well.
Not all bicycle hubs are exactly alike. Be sure to refer to your owner's manual for specific details that may be applicable only to your bike.