Wheel bearings and steering stem bearings are parts that are difficult to notice when the weight of the vehicle is on them. On the contrary, they are often already damaged or in trouble when they are clearly uncomfortable, and it is costly to repair them after they are broken. To prevent this from happening, try to float and rotate the tire once in a while.
Bearings are the power behind the scenes
There are two types of sealed bearings with rubber covers: contact type and non-contact type. The contact type has an advantage when it comes to dust and water resistance, but the non-contact type is superior when it comes to friction loss.
When replacing the bearing, check the service manual to see which side of the wheel hub (left or right) should be driven in first, and drive the side to be driven in first until it hits the wheel hub, and drive the side to be driven in later until the inner ring hits the distance collar.
Many motorcycle users are particular about their suspension, tires, axle shafts and other parts of the motorcycle. A motorcycle that feels light when you push it and walk on it, with little friction loss, also feels good in other areas such as braking, throttle control and shift feeling.
Wheel bearings play an important role in this process. Even if you change to tires with higher grip or axle shafts with higher rigidity, there are not that many users who also the bearings. However, the higher the performance of the tires and suspension, the greater the load on the bearing that acts as a bridge between the wheel and axle shaft.
Wheel bearings have always been ball bearings (although there are some examples of tapered roller bearings in some foreign motorcycles), and there are no factors that lead to increased performance on their own like tires or suspension. The bearing is press-fitted into the front hub, and the set position is determined by the distance collar between the bearing and the collar set from either side of the hub, and the axle nut is tightened to ensure rigidity.
In the case of the rear tire, in addition to the left and right side of the wheel hub, bearings are also incorporated in the driven flange where the driven sprocket is mounted. The distance collar and driven flange collar determine the positional relationship, and the axle nut is tightened to ensure rigidity.
The bearings are the reason the tire turns so lightly when the axle nut is tightened, but wheel bearings cannot just be pressed in randomly. Depending on the machining of the bearing holder part of the wheel, it is decided which of the right and left bearings should be pressed in first. For example, if the right side is pressed in first, the right side bearing is pressed in until it hits the bottom of the holder, while the left side bearing, which is pressed in after the distance collar is inserted, is not pressed in until it hits the bottom of the holder, but is pressed in when the inner ring hits the distance collar.
If this is not done and both the left and right bearings are driven to the bottom of the bearing holder, the inner ring may be pressed against the distance collar and become misaligned. Bearings are designed to perform at their best when the center of the grooves in the inner and outer rings and the steel balls are aligned in a straight line, and are not designed to be misaligned when mounted in a wheel.
However, in the manufacturing process of mass-produced wheels, there is a slight tolerance in the distance between the bearing holders, and it is inevitable that there will be slight individual differences in the length of the distance collar. Therefore, one side of the bearing is press-fitted to the bottom of the holder, and the other side is press-fitted to the point where the distance collar contacts the inner ring, so that no stress is placed on the bearing.
They are more delicate than you might think, but once they are in the wheel, they just keep on turning. Bearings are like the power behind the wheel.
- Point 1: When hammering a wheel bearing into a hub, the order of hammering on the left and right side is often fixed.
- Point 2: The tightening torque of the axle nut is important to ensure rigidity by combining the bearing and collar.
Bearing grease doesn't always last forever.
I'm not sure if it's foreign matter or lack of lubrication, but the retainer is destroyed and the steel balls are unevenly distributed in the bearing. If it gets this bad, you should be able to figure out what's going on because the tire won't rotate smoothly before that.
The seal can be removed by inserting a precision screwdriver or pick tool between the inner ring and the rubber cover and gently lifting it. Be careful because the metal plate on the back side of the rubber will be bent if you handle it roughly.
Spray parts cleaner and wipe with a cotton swab to remove old grease and grease up. By changing the type and grade of grease used here, friction loss can be reduced. The wheel bearings are the key to the rotation of the tires, so the tuning effect is significant.
Bearings built into the engine, such as crankshaft journals and transmission shafts, are constantly lubricated by engine oil. In contrast, wheel bearings and stem bearings cannot be lubricated with liquid oil, so they are lubricated with grease.
Used for wheel bearings are available in open, sealed and shielded typesBoth seal type and shield type have a part to cover the gap between inner ring and outer ring. Both the seal type and the shield type have a part to cover the gap between the inner ring and the outer ring, and the shield type has a metal plate that does not contact the inner ring, while the seal type has both non-contact and contact types.
Comparing the open type and the seal & shield type in terms of waterproofing and dustproofing, the latter is naturally superior in performance. In addition, grease is sealed from the beginning in the seal and shield type, and it is said that cleaning and replacement are unnecessary.
However, it is important to note that some motorcycle wheel bearings may use a single-seal type. A single seal is literally a bearing that has a seal or shield on one side only and the other side is open. If you remove the wheel and remove the dust seal that is pressed into the hub, you will be surprised to see the seal and shield from the outside of the wheel, but if you pull out the bearing and look inside, you will see the ball and retainer in full view.
With this single-sealed bearing, dirt can enter from the inside of the wheel hub, and if the rider continues to ride without noticing this, the inside of the bearing may be damaged. Also, the grease that was originally applied to the wheel bearing will deteriorate and flow, and even if friction increases a little due to poor lubrication, the wheel bearing will still rotate even though it doesn't want to. When the pressure exceeds the limit, the retainer will break and the steel ball will come to one place as shown in the picture. When this happens, you will not be able to ride the motorcycle and you will need to replace the bearing.
The rubber seal is normally a non-removable part, but it can be removed with a pick tool or precision screwdriver. However, you can check the condition of the steel ball and retainer, and grease it up if you remove the seal.
- Point 1: There are open, sealed and shielded types of bearings, and the sealed and shielded types are sealed with grease.
- Point 2: Sealed bearings can be cleaned and greased up by removing the rubber seal.
You don't have to take the tire off every time, you can just float it and let it idle to see how it's doing.
Before greasing or replacing the bearing, first turn the inner ring with your finger to see if there is a rumbling sensation. Since the bearing is an inexpensive part, you can replace it without hesitation if you feel any discomfort. In that case, check the hammering order and pay attention to the hammering depth.
Greasing the wheel bearings is not essential maintenance that must be done regularly over a period of time or distance; some motorcycles can travel 50,000km without any problems, and moisture and debris ingress can damage them in a much shorter distance.
As a preliminary step to greasing, it is effective to check if the inner ring rotates smoothly by turning it with your fingers. If it does not rotate smoothly and feels rough, there is a possibility of insufficient lubrication or foreign substances. The bearings used in the wheel are one of the cheapest parts of the motorcycle, so if you feel any discomfort, it may be safer to replace them than to grease them up.
If you don't want to take the trouble to remove the tire, you can try lifting the tire off the ground and shaking the wheel back and forth. By shaking the wheel with no weight on the tire, you can easily feel the rattle of the bearing.
Most problems with wheel bearings are only noticed when they occur, and there is no such thing as a preventative measure. However, considering the fact that the wheel bearings are made of metal and are lubricated with grease, there is no doubt that they are an area that should be taken care of.
- Point 1: By lifting the tire off the ground and removing the load, it becomes easier to grasp the condition of the bearing.
- Point 2: It's easy to see the bearing rattle when you shake a wheel that has been lifted off the ground.
