What is a ball bearing and why it is needed in the suspension of the car
Mechanical nodes of the modern car are saturated with all kinds of nodes, providing a comfortable and safe ride. From old to new car models, most of the details are upgraded, subjected to improvement. Progressive materials and manufacturing technologies are used. One of the important elements in the suspension, which designers and engineers pay considerable attention to when designing a car, is the ball bearing. The safety of the driver with passengers and surrounding road users depends on the quality of its manufacture, design features and possible malfunctions.
Why do you need a ball bearing support?
Usually, what is a ball bearing in the car, novice motorists learn from more experienced colleagues, when indirect signs of suspension malfunction are manifested. There may be extraneous noises in the wheel area or there are other factors. In a car, an element such as a ball bearing is not only located closer to the wheel. Similar connections can be found in different parts of the car:
- in the steering trapezium;
- on the camber arms;
- in the area of hood gas stops attachment, etc.
In fact, in terms of meaning, the more correct name for the unit is the ball joint. When a unit is called this way, its essence is clear.
Important! The main task of the ball joints is to provide freedom of movement for each of the wheels in the horizontal plane, simultaneously blocking the freedom in the vertical plane.
To understand how many supports are installed, it is necessary to consider the type of suspension. The factor affects how many ball joints the engineers have implemented in their brainchild. The simplest MacPherson suspensions make do with two pieces, which are located at the bottom. Increasing the number of wishbones entails increasing the number of hinges. Double wishbone systems offer both bottom and top mounting of the unit. German brands like Audi or Volkswagen can have up to five ball joints per wheel on one side. Just a few decades ago, the predecessors of spherical elements were kingpin counterparts. They were heavier products that needed regular lubrication. The principle of their operation implied the possibility to rotate only in one axis, which was detrimental for the drivability. During operation, the ball bearings operate in such a way that they take the impact of the bumps of the road. This puts a tremendous strain on the metal product. However, engineers are not trying to make a ball bearing with maximum strength, giving it a shape that, if necessary, it can be easily replaced by unscrewing a few bolts. The assembly has become a consumable.
The classic design of ball joints
The standard design of the ball bearing unit involves the main components:
- metal body;
- pin with a ball head;
- spring loaded;
- corrugated rubberized dust cover.
A sufficient amount of lubricant was packed inside at the factory. Good quality lubricant was sufficient for long mileage. Mechanics should check the integrity of the dust cover and the quality/volume of lubricant at each service and, if necessary, use a grease gun to press the required amount. In later models, some of the metal parts have been replaced by plastic counterparts. Also now there are no springs inside (they were discarded for lack of use). The spherical head of the finger is now rolled in a hemisphere of liners. In modern models, the latter are no longer made of plastic, but of more durable and sturdy nylon. Manufacturers have started making two types of ball joints, so the supports come in maintenance and maintenance-free versions. On most new cars, there is the second type of assembly. It has no disassembly option and has a built-in grease nipple for adding grease. Sometimes there are intermediate types, relating to the non-disassembled versions of the design, but having a lubricator.
Ways of fastening
The main differences between modern spherical joints are not so much in the design as in the methods of attachment. This is due to the cost of labor-intensive maintenance, replacement. The best option, acceptable for the car owner is considered to be fixation of the hinge body to the suspension arm by means of a threaded or riveted joint. The method allows you to quickly dismantle a worn unit, if necessary.
Later, manufacturers began to abandon this method in favor of integrating the lever in the suspension. This design had the disadvantage of having to replace the lever assembly, even if it was not worn. The advantage was a lighter design. Although there’s an opinion that this system was lobbied by marketers for the sake of increased profits from the sale of parts, because it is necessary to change the lever assembly. Some automakers have made a compromise and refused the rigid fixing to the lever. The alternative was a retaining ring. The support was just pressed into the lever. Examples are the Jeep Patriot or the Opel Zafira C. In that case, the replacement will require a press or other type of force.
Locking at knuckle
If the support is on the arm, it can be attached to the knuckle. Such features are characteristic of the ball joint on the lever. The design can have three variants:
- The threaded pin is connected and secured with a nut, which must be cotter pinned;
- a self-locking nut, which has an inner retaining ring, is used for fastening;
- a coupling bolt is installed, which is rare, such as on the Hyundai Santa Fe from 2006.
The last point is less acceptable, because if it breaks and needs to be replaced, it may turn out that the threads are seized. The negative factor is the need for a special wedge used to loosen the ends of the cam bracket where the ball stud is secured. Sometimes, even in the great suspension designs of German cars, the stuck bolts create a lot of difficulties during disassembly. It is impossible to save the situation by heating the cam or freezing the bolt. Even a ten-ton hydraulic press doesn’t make it possible to unseat the bolt. For example, the owners of Audi A6 have to pay 400-500 dollars. In some cases, engineers move the joint to the knuckle from the lever. Although such a solution does not add to the repairability. Then there are several ways to fix it:
- bolting;
- Pressing;
- in the cam bracket the use of a tie bolt.
There are advantages and disadvantages in each case.
Dust cap
An obligatory attribute of the main suspension joint is the dust cover. It is used both on removable and non-removable structures. The detail refers to replaceable. Specialists recommend checking its condition no less frequently than 10-15 thousand km. mileage. Timely replacement of worn out dust cap will help to save on the repair/replacement of the entire ball joint. Its task is to block the penetration of moisture, dust and dirt to the rubbing surfaces, which contributes to the rapid wear of the metal parts.
Possible ball bearing defects
Even a novice motorist can independently detect signs of ball bearing wear by indirect signs. It is necessary to pay attention to the behavior of the car during turning. When the driver has to make special efforts, or a characteristic sound (creaking) is detected, there is a high probability of breakage of a ball bearing. An additional negative sign is the manifestation of a knock while driving at low speed on an uneven surface. We recommend diagnostics when you notice such symptoms of wear, as instability of front wheels and their wobbling sideways in the process of rectilinear movement. Many experts consider uneven wear of the car tires to be a sign of ball bearing wear.
How to check a ball bearing on a car
Proper use and timely maintenance of ball bearings helps to prolong their working life. Usually the service life of modern spherical joints in cars, depending on the make, reaches 30-100 thousand km of run. Cars with the following criteria can fall into the risk zone with premature breakdowns:
- the dust cover on the ball joint is torn;
- the car is often driven on bad roads;
- the unit has insufficient lubrication;
- the pins of the ball joint have worn down, there is a gap, leading to looseness.
To check the condition of ball joints you will need an elevator or a jack. After lifting the car, the wheel being tested should be able to turn freely. The motorist should take hold of the upper and lower edge of the wheel and gently rock it in a vertical plane. You can ask your helper to turn the steering wheel slightly. You will be able to hear the wear at a certain position of the wheel. However, backlash in some cases is a consequence of insufficient tightening or failure of the hub bearing. The play is also caused by damaged arm silent blocks. An additional test will be necessary. Use the flat part of the crowbar to determine if the ball joints need to be replaced. Insert it into the gap between the lever and the pivot stud. Create a small amount of force on the handle and watch the assembly. There will be no backlash if the ball joint is serviceable. Negative factors will be the tapping and clicking noise that occurs while pressing on the handle.
Conclusion
Learning to self-diagnose ball bearing failure, the car owner will protect himself on the road. Also, if possible, it is required to add grease under the dust cover in a timely manner or conduct a complete replacement of the node.
How do ball bearings work in the suspension? Why are they integrated into the suspension arms, why do they wear out and how difficult is it to change them in a modern car? Let’s look into this question in all its details.
The ball bearing is, structurally, nothing more than a pivot that attaches the wheel hub to the suspension arm. Its main task is to give the wheels freedom of movement in the horizontal plane and prevent it from moving in the vertical plane. Actually, ball joints are used not only in hub supports – they are also found in camber arms, steering geometry, and even in hood gas struts.
But up to a certain time, instead of moving ball joints on steering wheels, a kingpin joint was used – heavy, requiring periodic lubrication, and most importantly – providing the wheel only freedom to turn on one axis, which had a negative impact on drivability.
The designers understood that the ball bearing would take every impact from the road, so the wear and tear work would become enormous. There was no sense to make a detail with a particularly durable diamond coating, therefore it was deliberately turned almost into an expendable item. So that in case of need it was possible to replace it without problems, having unscrewed a pair of bolts and a nut.
Design of the ball joints
Initially, the ball bearing was a housing in which was installed the ball pin, compressed through a metal plate with a spring, and covered with a dust cover. To keep the pin from wearing out after two days, they put grease in it and instructed everyone involved in maintenance to regularly check and replace the grease in the housing by pressing it in through the grease nipple.
Then came the era of plastic and the spring was gone from the design. The ball part of the pin was placed in a hemisphere formed by liners of the aforementioned material. Since then, the design has essentially remained the same, except that the plastic has been replaced by a more wear-resistant nylon.
Ball bearings were divided into maintainable and maintenance-free, that is, with and without the possibility of disassembly and with oil nipples, respectively. But the closer to the present decade, the less use was made of collapsible bearings. The ball bearings with grease nipples for lubrication remain an echo of the era, but nearly all cars have long had maintenance-free bearings.
How many ball bearings are there in the suspension?
It all comes down to the type of suspension. The simplest McPherson’s have two ball joints – they are on the bottom. The more levers, the more ball bearings. On double wishbones, there are upper and lower ball joints, and on the most complex suspensions, mostly Volkswagen and Audi, there can be five per side.
Arm mounts
Now, the entire classification comes down not to the type of design of the ball joint itself, but to the way it is mounted – the cost of replacement is very much dependent on this. The simplest and most peaceful to the owner of the car design – with the attachment of the support body to the suspension arm with bolts, nuts or rivets. In this case it is not difficult to detach worn out ball joint from the lever. It would seem that the design is perfected, but since the late 1990s, engineers have been gradually abandoning it in favor of the support integrated into the suspension arm. There is a compromise design, which has no attachment elements to the lever, but has a locking element – a retaining ring. In this case, the support is simply pressed into the lever (for example – Zafira C and Jeep Patriot). To replace it, you will have to use a press or other forceful way (more about this – below).
Attachment to knuckle
The basic types of attachment to the lever are considered, now let’s turn our eyes to the fixation of the ball bearing to the knuckle, provided that the bearing is on the lever. There are only two options here: the support pin can be connected and fastened with a nut, which is either cottering, or a self-locking nut with an inner retaining ring is used. An alternative fastener option is a tie-down bolt, such as the 2006 Hyundai Santa Fe. The latter option is more troublesome, as the bolt, in practice, is prone to sticking. Take Audi A6 C7 at least: there is a wonderful design of the front multilever suspension, where ball bearings of the upper arms are connected to the knuckle and fixed by one long tie bolt, which very often gets so stuck that it is impossible to take it out. Neither heat of the cam (it is made of aluminum alloy), nor cooling of the bolt, nor even applying five or even ten tons on hydraulic press doesn’t move this ill-starred bolt even a millimeter. And as it often happens in such a case, the owner finds out that his purse is emptied by 400-500 dollars – such is an average price for a new knuckle for A6 C7.
In an effort to optimize the suspension design (not always for the sake of maintainability), the ball bearing was moved from the lever to the knuckle. It can be pressed in (SsangYong Rexton, Mercedes-Benz CLS W219), bolted (VAZ 2110) or fixed with tie bolt in the knuckle bracket (Subaru Forester SG). Each method has its own advantages and disadvantages.
In the first option to replace the ball joint would have to remove the entire knuckle, and it is self-evident removal of the caliper and disk with disconnection from the upper (or upper, if they are two) and lower levers. The second and third option is much easier, because all you have to do to replace it would be to disconnect the lower arm from the ball bearing.
The ball bearing has them at all times, regardless of whether the support is removable or integrated into the arm. And they are replaceable! A small indulgence from designers and marketers. But after cheerful news I have to distress: how often do you look under the automobile and look at dust pads? The most responsible – once in 10-15 thousand kilometers during periodic service maintenance, and the majority of car owners saw their car from below once or twice (when a master showed wear of suspension) or didn’t see them at all. No matter how it is, but there is little probability to detect a cracked, but not damaged dust cap in time, so you will pay attention to it only if it will come to the end, and it will be automatically replacement of a ball support. The circle is closed. Below is a description of how the dust cover can collapse and how to replace the ball bearing almost in the field using the Jeep Patriot as an example. What made you decide to replace it? I have paid attention to a horrible squeak from the side of suspension when turning a steering wheel.
Causes and Consequences of Ball Bearing Failure
As stated above, the support was invented as a replacement for the kingpin, but getting rid of it did not get rid of the forces acting on the ball joint. If you ask an almost philosophical question: “So why do ball joints wear out?”, the answer will consist of three main points (there is a fourth – time – but it is not interesting, because it is clear). First: increased shock loads on the suspension when passing, for example, on the tramway at an obscene speed or normal operation of the car in unusual road conditions, which we are not surprised. Second: the lack of lubricant where it should be (remember the oil cans?). And, at last, the third: destruction of support anther.
As for design features of suspensions and their influence on wear, you can say the following: any ball bearing, no matter how it was installed – on the lever or on the knuckle – will wear out due to impacts and friction. And if you want to save money and nerves, you need to look behind a wheel more often, and do not shout to yourself “Banzai” at the sight of approaching misunderstandings in the form of potholes.
Example of a ball bearing replacement
I did not have special tools, but I had a great desire to solve the problem quickly, so I could leave on the road and arrive on time. Therefore the car on an elevator, keys in hands, sleeves up to the elbows. First of all – ball bearings. In this case both “died”, but even if only one has died, it would be necessary to replace them both sides all the same. It is a written rule for all automobiles, and it concerns repair of running gear and braking system elements. If the right side is broken, it means the left side is also in for a hit (with determining the cause of the asymmetry in the breakage, of course).
Here we go. We unscrew the bolts fixing the lower front suspension arm to the subframe. It is not easy – bolts are a little bit stuck. However we do not unscrew them out completely as the arm is also connected to knuckle.
So the next step is to unscrew the bolt that secures the ball hitch of the lever. By the way, this is not the most successful connection option that exists. I already wrote above that to press out the support in this case you need a special wedge to unclamp the ends of the cam bracket. In our case there was no special device, its role with dignity was performed by a chisel and hammer.
When the arm is disconnected, we finally unscrew the bolts fastening to the subframe, and voila – the arm is in heavily oily hands of the professional. The pin was just dangling and was as corroded as the material allows. There was no dust cap. The owner of the car got a few gray hairs as he realized that at any moment the lever could just rip out, and then…
After sending the owner to drink tincture of valerian, we continued the struggle. The mechanic after examining the lever noticed that the silent blocks had not much time left as well. Though, according to the assurance of the owner, who had come back already calm, these parts were replaced relatively recently and in general, “it can’t be!”
The reason was explained by a pro: in order to pass the time for repair, some representatives of the working class tighten the bolts fixing the arm to the subframe on the unloaded suspension. The car hangs on the elevator, and the mechanic with a torque wrench pulls the bolts with the tightening torque, specified, for example, in the repair manual. Everything seems to be correct, but not quite. Rarely do you read the manual, where it says in black and white: “The final tightening of the elements of fixing the arm to subframe is made with loaded mass of the car suspender”. This means that the torque specified by the manufacturer must be applied after the car is mounted on the surface – this way the silent blocks “settle” and the gaps necessary for normal operation are eliminated. Otherwise it will turn out the way it did on our car. And though the silentblocks didn’t need to be replaced immediately, a hole was to be formed in the family budget of the owner in the near future.
Let’s get back to our “sheep”. The ball bearing is fixed in the lever by friction and one locking ring. Consequently, we take off the circlip and if there was a dust cover – also it and ruthlessly knock the bearing out of the lever. In idea this operation needs a press, but it is done and there were no questions.
The set of the new ball bearing includes: the bearing itself, a dust cap and a retaining ring, and also a special grease. We install the cradle in the lever, select a mandrel by size and hammer it into the lever until a groove for the retaining ring appears over the top surface of the lever. And a press was necessary for this operation (at least so it was written in the repair manual), but there was no press and the necessity of urgent repair was.
After a great deal of trouble, we install the retaining ring. We apply lubricant from the kit to the pin of the ball bearing and put grease in the dust cover. As it turned out, there is no snap ring for the dust cap (in this version), it is just put on the support body, and that’s all. Afterwards it turned out that the dust cap was made as a sealing collar – with an elastic belt, maybe even with a spring inside. It was rather tightly seated on the support.
Let’s mount the lever on its place. Connect the lever to the subframe, screw in, but do not tighten finally the bolts of its fastening. According to the advice of an experienced person, it is advisable to apply some nigrole on the threaded part of the bolts to make it easier to unscrew them later on. The pin is not dangling in the new ball bearing, therefore, you will have to sweat a little in order to guide it into the fixing bracket on the knuckle. Our mechanic, in order to increase leverage, installed a ring wrench on the pin and moved it to the needed position. The ball bearing was connected, installed and tightened the coupling bolt. Lowered the car on the surface and tightened the bolts fixing the arm to the subframe finally. Went back a dozen or so lines above and repeated all steps for the second arm.
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