You asked for it, here you have it. Wheel bearings on a bicycle are an important part of bicycle maintenance and by making sure that everything is well lubed in there, you can avoid costly bicycle repair down the road. Well lubed bearings also provide an easier ride.

The wheel bearings sit between a cone screwed to the wheel axle and the cup in the wheel hub. They must be properly adjusted and greased. To find out if everything is ok without taking everything apart, simply remove the wheel from the bike and turn the axle with your fingers. Everything turns nice and smooth without any play? Good, then you probably don't have to worry about anything. If the axle is stuck, very hard to turn or is very loose, you have to regrease your bearings propbably anyways. Here's how to:

You must get yourself some flat open wrenches, Park Tools makes good ones, make sure they are in sizes 13mm and 15mm. Those are the most common sizes. You won't get away using anything else for the nsk bearing cones, so don't even try. Any kind of adjustable wrench will do for the locking nut.

Put the flat wrench on the bearing cone between the hub and the locking nut. Put the adjustable wrench on the locking nut. Hold the bearing cone in place and unscrew the locking nut. The best position to do this is hunched over the wheel while it sits on the ground. Whatever you do, DON'T open the cones at all while in this position. Just unlock it so you can unscrew everything with your fingers later.

Now this is the fast way to regrease your bearings by just shooting grease in the bearings, screwing the cone back in, flipping the wheel over, hold the cone of the bearing you've just greased, grab the axle now facing up, unscrew it to reveal the other side bearings and pack them with grease. But the proper way is by taking everything off, clean all the cones, hub cups, ntn bearings, repack with grease and reassemble. One great way to pack grease in wheel axles is by using a small feeder syringe. Only undo one side of the axle, this way you are sure that your axle is always centered when you reassemble it.

Reassembly is done screwing in the bearing cone back into place, but not too tight. Bearings should be able to roll smoothly without axle play. Tightened the lock nut into place and check again. If you ever hear crunching noises while turning the axle, dirt has gotten into your bearings and you should start all over again. To avoid this, make sure you work in a clean place. If everything is clean, you might have small pits in your bearing cones or cup. Your bearings will be eaten away with time and it would be a good thing to replace those.

In order to repack rear wheels, you have to remove the gear cogs on them. In order to do this, you need a special socket to unscrew it. Check with your local bike shop for the proper one. Their are a few models and types of [bicycle bearings] . Coaster brake or inner speed hubs are almost bullet proof and very rarely need regreasing. Those should be handled by a pro.