WHEEL BEARING SERVICE TUTORIAL
Although most of your bicycle pedaling efforts will be thrown to the wind (literally), some of your energy will be eating up by friction from moving parts such as bearings, chain links, and even the compression of the tires on the road. Bearing friction does not account for much of your power loss as long as your bearings are in good working order and properly lubricated. This basic tutorial will show you how to remove, clean, reinstall, and then set the clearance on your bicycle hub bearings for optimal performance. Here, I will be using a 20 inch BMX from wheel with a 14mm axle, but this tutorial can be applied to any front or rear bicycle wheel that uses the very common cone and cup style bearings.
The term cone and cup refers to a type of bicycle hub that has a set of ball bearings sandwiched between a cup that is built into the hub shell and a cone shaped nut that is threaded onto the axle. Basically, the cone and cup are the bearing races that the balls ride on. With the exception of some seriously beefy mountain bike hubs that include large diameter hollow axles, most bicycles will have a cone and cup style bearing system. It is easy to identify this type of hub by looking for a locking nut sitting on top of another nut that has only two flat sections as shown in this photo. The nut with the flat sides is the cone nut, and it reaches below the sealing cap you can see and into the hub to connect with the ball bearings.
To disassemble a cone and cup wheel, you only need two wrenches, but one of them is a special kind of wrench specifically designed to remove bicycle cone nuts. This wrench is of course called, a cone wrench! As you can see in this photo comparing the cone wrench along with a crescent wrench, from the top, it looks similar to a box wrench. The crescent wrench will be used on the locking nut, and the cone wrench will be used to grip the flat sections of the cone nut it was designed to fit. There are several sized of bicycle cone nuts, and for the wheel I am working with, I needed a 19mm cone wrench.
As you can see in this side profile, the cone wrench is a skinny dude. With a total thickness of no more than 3/16", the cone wrench will fit nicely into the flat section of the cone nut where a standard wrench would have no chance. The reason for keeping the nuts as low profile as possible is to reduce the clearance between the hub and the fork leg dropouts so there is no wasted space. A cone wrench can be purchased at any bicycle shop for a few bucks, but if you are on a tight budget, you could also make your own cone wrench using a grinder and an old wrench of the correct size. You can see a tutorial on how to make your own cone wrench on our Tutorials Page.
You can start by removing the axle nuts from both sides of your axle by turning them in the counter clockwise rotation. If your axle is slightly rusted or has dinged up threads, you may need to hold onto the locknut on the other side using a wrench in order to get the nut to turn. A little cleaning with a wire brush and some 10WD-40 will help release the nut from a badly damaged or rusted axle, but if your axle is in really bad shape, you may be looking at a replacement.
You can also remove the main axle washers, taking note of the serrated side, if they have one. Usually the serrated side of a washer will face towards the hub, as these small "teeth" help keep the washer from turning as you tighten up the axle nuts.
In this photo, you can see why a regular wrench cannot be used to remove a cone nut; it's simply too thick to get a grip on the flat sides of the nut. I already know what you're thinking; "why not just take my grinder to a wrench and make my own cone wrench"? Yeah, that does indeed work!
Here you can see how the thin cone wrench fits perfectly into the slot on the cone nut. I am using a 19mm cone wrench, which is what I needed for this 14mm axle BMX wheel. This is a somewhat larger cone wrench, as most bicycle wheels have axles between 10mm and 12mm in diameter.
To remove the hardware on one side of the axle, you must first break the lock between the top of the cone nut and the underside of the lock washer. Normally, you will only want to remove the hardware on one side of the axle, leaving one side secured. This way, you won't need to worry about centering the axle, which is a little more complex of a job when dealing with a rear wheel. Start by gripping the cone nut with the cone wrench, and then grip the lock nut with the other wrench so that both wrenches are about 45 degrees apart. Now, force the wrenches away from each other until the locking nut frees itself in the counter clockwise rotation.
Once the grip between the locking nut and cone nut has been broken, the locking nut should be easy to unthread by turning it in the counter clockwise rotation by hand. If your axle is not in perfect condition, hold the locking nut on the opposing side of the axle with a wrench and use another wrench to remove the locking nut all the way from the axle. Each time you unthread or thread a nut, this helps to clean up the threads somewhat, so if the nut was difficult to turn on the first round, it may be easier next time. This process is called "chasing the threads".
Some locking nuts may have serrations (teeth) on one side. Take note as to which way these were facing in relation to the hub. If in doubt, put the teeth towards the hub, as they will help maintain a better lock with the top of the cone nut.
You may also need to hold the nut on the other side of the axle and use the cone wrench to get the cone to unthread the first few turns. From there, it will be as easy to remove as the locking nut was. If you have difficulty turning it off by hand, hold the lock nut on the other side with a wrench and use the cone nut to spin it off the rest of the way. Often, the threads are a bit flat where the edge of the dropouts where sitting.
Typically, wheel bearings are just loose packed balls, so as your cone nut is coming loose, be prepared to catch any loose balls that may fall out. I like to work over an old butter container or over a rag on a workbench so that the balls to end up on the floor. As you well know, "Murphy's Law" includes a special clause just for bearings that ensures that you shall never find a bearing that hits the floor, no matter how well lit or clean your garage may be. The only exception to this rule is if you no longer need the bearing, at which point you will either trip over it or find it rattling around inside some delicate machinery such as a gearbox. I kid you not, be careful with those little bearings!
If your wheel lubrication is still somewhat fresh, all of the balls will be nicely packed inside the cup as shown here. Normally, the grease will dry up after a few years, but this wheel has been through this maintenance exercise once per year, so it's still looking good.
The dust caps are pressed into the hub and have the job of keeping the dirt out while at the same time keeping the lubrication in. The dust caps have a metal outer ring and typically include a rubber seal that will ride on the smooth face of the cone nut. Budget hubs may not include the rubber seal, so it becomes even more important to lube up your wheels once per riding season.
To remove the dust cap, place a flat screwdriver with the blade under the edge of the metal ring as shown here. Push down on the screwdriver to pry out the dust cap. It should just pop out of the socket with a little effort, but if it's stuck in there good, you can pry it at various different positions until it is released. Place the screwdriver blade as far over as you can so you don't rip the rubber seal surface when you are prying the dust cap out.
With the disc cap removed, you now have full access to the loose ball bearings. Some wheels actually include bearings with a retaining ring, so you can remove the bearings as one single piece, but typically, the balls will just be loose. Notice how much grease still remains under my dust cap. This wheel actually didn't need to be regreased, but it was the nicest looking wheel I could find for this tutorial. Most of my other wheels are already living on DIY trikes, quads, and lowracers!
A good way to remove all the bearings without losing them is to place the hub over a container and then push them all out through the center of the hub. You could try to lift them out by hand, but being sticky with grease, they will probably stick to your fingers and end up on the floor never to be seen again. I have seen this too many times now, so the butter tub is the only way I do this now. Oh, and don't forget to count how many bearings you have on one side so you know if any are lost on the reinstall.
Push the bearings through the center of the hub with a screwdriver or small object. If the bearings are greasy, make sure they are not clinging to the screwdriver when you lift it out to flip over the wheel. Before flipping the wheel, give it a bang down on the rim of the container, which may release all of the balls on that side. Balls are easier to remove when the grease has dried up, but are more likely to be in bad condition from rust.
Now you can clean the axle and bearing components. A rag with some cleaning agent like varsol or paint thinner will work well for removing old grease and grime from the axle and threads. Grab the part and give it a good scrub in the wet rag until you see the base metal. If your axle is rusted slightly or really caked with grime, then try a wire brush to clean it.
Give the cone nut a good cleaning with the rag, paying attention to the bearing race surface on the bottom side of the nut. This surface rides against the balls, so it needs to be free of rust, pits or any cracks. If there is damage on the bearing race surface, you will need to replace the cone nut.
Clean all of the ball bearings by placing them all on the rag and then folding it over to wipe them off all at once. Then take each ball and give it a quick inspection, making sure the surface is still somewhat shiny, and not rusted in any way. Rusted, cracked or deformed balls will need to be replaced, but at this point, the cups and cone are probably worn out as well.
The cleaned ball bearings should have a chrome appearance like these ones. The ball will dull slightly as they are worn, but if they take on a rusty color, or have a tarnished surface, it will be time to replace them all. It's not a good idea to mix balls, unless they are from the exact same model and age of hub. Balls may look the same size, but unless you measure them with a vernier, it's difficult to tell just by looking at them.
The last part to clean will be the cups in the wheel hub shell. Give them a good wipe down with the rag and cleaning agent to get right to the bare metal. Once again, inspect the parts for signs of tracking, pits, or cracks. The cup bearing surface won't be as shiny as the bearings, but it should be clean, and not have any visible imperfections where the balls are to ride. Notice the cup is an insert that has been press fit into the hub shell. The reason for this is because it is made from very hard steel, which make a bearing surface. An aluminum hub shell could never be a bearing surface because the metal is too soft.
The balls will ride right in the edge of the cup, which is why this track is very smooth and accurately machined. If you see and cracking of the cup or rusting in the bearing track, you will probably have to replace that hub. You can in fact pop out the cups, but it is unlikely that another set from a different hub fill fit, so typically these are non replicable.
To lubricate your wheel bearings, you will need some type of bearing grease. I use general purpose hardware store bearing grease for all of bicycle and wheel bearings. There are some expensive "designer" bicycle bearing grease kits available, but I can't see the point in spending twenty bucks on something that will last a single season. This 9 dollar tube of grease I am using is over 5 years old and had greased every bearing on every bike on the AtomicZombie Website as well as all the robots on the LucidScience website!
Once you have the grease installed in the bearing cups, you can now install the dust caps. Most dust caps are designed to be fit in only one direction, so place them over the hub opening in the same manner in which they were removed. If you have a good eye for detail, then you may notice that I am putting the dust caps back in backwards here, with the rubber seal side facing down. These particular seals work in either direction, and I prefer the look of the gold edge on the outside. Yours may not be reversible.
To reinstall the dust caps, line them up evenly over the hub shell opening, and then carefully tap them down with a non metallic object, working your way around to push them in a little bit at a time. I find that a screwdriver handle is perfect for this job, as it won't dent or ding the thin metal ring or the hub shell. Don't smash the dust caps into place, or they will just bend.
To reinstall the loose ball bearings, simply stick them into the grease one at a time. If your bearings include a retaining ring, then just add a bit more grease to the inside of the ring (the spaces between the balls), and then drop it in place. Place loose balls as close to each other as you can, placing them until you have used half of the balls for one side of the hub.
With all of the ball bearings installed for one side of the wheel, place the axle through the hub as shown here, and press it down into the ball bearings to hold them in place while you flip over the wheel. Rest the wheel on the axle so it pushes up into the hub, holding the ball bearings in place while you work on the other side.
If your axle set had a thin washer between the cone nut and locking nut like mine did, then install it now. Now install the locking nut all the way down and hand tighten it against the cone nut. Remember to place the teeth of the nut towards the hub to gain a better lock against the washer or cone nut.
To securely fasten the locking nut to the cone nut, use the cone wrench and the other wrench in the same manner you did when unlocking the nits, but this time force the wrenches towards each other. This will tighten the locking nut against the top of the cone nut in the clockwise rotation. Press the two wrenches together with a good deal of force to get a good lock.
To check your bearing tightness, grab the axle with your finger and thumb and give it a few twirls. It should spin smoothly, but have a bit of resistance. If you can twirl the axle with almost no resistance, or if you can move it from side to side or up and down, then it is too loose. If the axle is too loose, or is difficult to spin, then unlock the nuts and relock them again to get the correct setting. Sometimes the axle turns when you are locking the nuts, which may cause the cone nut to loosen a bit.
Install the main washers, making sure you place the teeth in the same direction they were when you removed them. This large washer is placed on the outside edge of your dropouts and stops the axle nut from digging into the dropouts when you are tightening your wheel. Without this washer, the axle may move as you tighten the axle nuts.
Pick up your reconditioned wheel and give it a twirl. The wheel should spin nice and easy, with only a little drag on the axle from the adjusted cones. By the end of the riding season, the cone nuts will need another adjustment from slight wearing of the bearing parts, so this is a good time to take everything back apart, inspect, and re-lubricate. Well, I won't hold you up any longer - go put that wheel back on your DIY recumbent bike and hit the trails!
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