What You Need to Know About Wheel Bearings
A wheel bearing failure at riding speed can lead to a serious crash, or if you get lucky, may just ruin some expensive parts, including wheel hubs, axles, etc. So don't neglect them, because they’re important and easy to forget about. The owner's manual or shop manual are good places to start for determining wheel bearing inspection intervals and service procedures. Most modern bikes have ball-type wheel bearings that are designed with seals that keep you from being able to add grease.
These sealed wheel bearings can last as long as you own the bike, if you treat them right. However, overloading the motorcycle, riding in deep water that goes over the hubs, directing a pressure washer or hose on the center hub areas, doing wheelies, jumps or riding hard on rugged terrain will reduce their service life, as will neglecting to lubricate bearings that can be greased. Observe the manufacturer's guidelines for inspecting and replacing wheel bearings, and change them whenever you notice excessive wear or looseness. So, how can you tell if they need replaced? It all starts with a visual inspection.
Tapered wheel bearings like these rusted BMW bearings are common on older motorcycles.
During tire changes is a great opportunity to check and maintain your wheel bearings. With the bike safely supported on a motorcycle jack or center stand, turn the tire and wheel assembly by hand and attempt to get the wheel to move side to side, to feel for any slack or play in the bearings. If you can feel looseness, the wheel bearings need further inspection.
When the wheel is off, push a finger in the hole where the axle goes and try to turn the bearing. If the bearing sticks as you turn it, or feels rough, it's faulty. Also look for any metal dust or rust around the bearings. If any of these problems are found, replace the bearings as a set. With the wheel off, stick a finger into the center hole of the bearing and feel how it turns by hand. It should be smooth and not feel loose or stick anywhere.
Order of Operations
Before you take things apart, visualize how the brakes, chain adjusters, washers and spacers are situated. Shoot some photos with your phone and set parts down in the order they are removed. I also place the spacers, etc., on the same side they came off, as this makes reassembly easier. An exploded view from a shop manual is invaluable. Note that on many bikes the center spacer can only fit in from one side.
Wear safety glasses when working with tools, and protect your skin with nitrile rubber gloves when applying grease. If your bike's wheel bearings can be greased, get wheel-bearing grease (the type recommended by your motorcycle manufacturer) and new grease seals as needed, before starting the job.
Tapered wheel bearings, which are usually seen on older motorcycles, may be able to be removed. Once removed, you can wash them in solvent and dry them using compressed air or a clean cloth. Do not allow them to spin with air pressure, even though it seems like fun. Carefully inspect the ball bearings and races for scoring, chips or other flaws and replace if any defects are found. Then repack using wheel bearing grease. Wheel bearings which are shielded on their sides can't be re-greased. However, if the bearings have shields on only one side, and seem a little dry, then it’s a good idea for some grease to be added. This may extend their service lives.
Go Easy on the Wheels, Man…
When removing bearings, go easy to avoid damage to hubs and wheels. And remember to always clean the area first. Next, remove any snap rings. There's more than one method for removing and installing wheel bearings. One way that requires minimal tools is to support the wheel's center hub on wood blocks and push the bearings out using a hammer and brass drift. Be sure the tool is only contacting the bearing and not pressing against the inside of the wheel hub as it may crack apart.
Tricks of the Trade
Wheel hubs are typically made of soft alloy, so care must be taken. When bearings don't come out easily, you can heat the hub around the bearing with an electric hot-air gun, which will help expand the metal and allow the bearing to be removed or installed easier. Another trick is to place the bearings in a freezer for a while first to shrink it before dropping them back in the hub.
Tools of the Trade
Several tools and methods can be employed to remove and install wheel bearings. One removal method employs a small slide hammer with two internal metal hooks to yank out the bearing from its center. Most removal methods other than a press may damage the bearings, so always replace them when removed by other methods.
Commercially made bearing and seal installations driver kits are recommended. It's also possible to make a small press out of threaded rod, with nuts, washers, and a socket used to press the bearing(s) in to the hub. If you don't have the proper tools or are unsure of yourself, bring your wheel(s) to a motorcycle shop or machine shop and have them remove and install your bearings using a hydraulic press.
Reassemble the parts in the opposite order you removed them. Bearings and seals must be properly seated, greased and seal lips lubricated. Ensure that all fasteners are securely tightened to factory recommended torques during the reassembly process. After completion, test the brakes and test ride the motorcycle in a safe place with full safety gear, before returning it to service.
Our friends at Rocky Mountain ATV MC built a great video that will help you visualize some of the concepts mentioned in this article. Remember that this particular How To video is aimed at dirt bike wheels, so if you plan to remove your streetbike bearings, check out some of the other great instructional videos on You Tube for a few more hints and tips.