As you ride your bike, normal use will eventually wear the cartridge bearings in the wheel hub. When you spin your wheel and notice grinding or rough sounds coming from the bearings, it's time to overhaul the wheel hub. When overhauling a hub that uses cartridge bearings, rather than replacing individual bearings, each entire cartridge is replaced. This requires a few tools and a vice with wooden blocks to remove the bearings without damaging the hub. Once the wheel is removed from the bicycle, the entire process takes around 10 minutes to complete.
Place the cone wrenches on the locknuts on one side of the axle. Loosen the locknuts with the wrenches and remove them from the axle. Repeat this step on the opposite side of the axle.
Pry the seals from each side of the hub axle, carefully, with the flat head screwdriver. Place one flange of the hub on top of two blocks of wood held in the vice so that the axle lies between them.
Tap the top end of the axle with the plastic mallet, firmly, to drive the axle downward and push the bottom bearing cartridge out of the hub. Use a drift, a metal cylinder the same diameter as the end of the axle, to continue driving the axle downward until the bottom bearing cartridge comes free.
Remove the axle and bottom bearing from the hub. Place the axle between the wooden blocks, resting in the bearing on top of the blocks. Tap the end of the axle with the mallet to remove the bearing from the axle itself.
Remove the hub from between the wooden blocks, turn it over and place it back between the wooden blocks. Place the drift in the hub and tap it with the plastic mallet to loosen and remove the other wheel bearing.