Replacing the support bearing of the front strut with the removal of the shock absorber and without
Content
MacPherson type front suspension, due to its simplicity, manufacturability and low unsprung masses, quickly captured a large part of the automotive market starting from the last quarter of the 20th century. One of its structural components, namely the upper support bearing, looks like a good example of how the most important advantage of the scheme, in terms of resource, can be turned into one of its weak points.
In more detail, what kind of node it is, what kind of malfunctions car owners have to face and how to fix them, read below.
What is a support bearing and a support of the front shock absorber strut
The base of the MacPherson type candle suspension combines a shock absorber and a spring, that is, one telescopic candle is capable of both acting as an elastic element and damping the energy of body vibrations relative to the road.
In other words, this assembly is referred to as a "suspension strut" or "telescopic strut".
From below, the rack is attached through a ball joint to the positioning lever, and a bearing support is installed on top, which allows the rack body with a spring to rotate about its own axis under the influence of the steering rod.
The upper support includes directly rolling bearings, housing, damping rubber elements and mounting studs.
On the one hand, the body is rigidly connected to the body glass, and on the other hand, the shock absorber rod and the spring support cup are connected to it. There is rotation between them.
Types of support bearings
The bearing must perform angular contact functions, and the more accurately it does this, the longer the car will retain its handling characteristics. Therefore, many different designs have been developed, there is no one single one yet.
Bearings according to their constructive organization can be divided into:
- by the nature of the rolling element - ball and roller;
- bearings with removable outer or inner races;
- integrated angular contact bearings of non-separable type;
- bearings without cages, which are a powerful cage with built-in rolling elements, support flanges act as tracks.
During assembly, a supply of lubricant is laid in the bearing, but its operating conditions are such that it is not enough for a long time.
What are the faults
Most often, the first signs of problems with the oporniks will be knocks in the suspension. A heavily worn and loose bearing will make this sound on every significant bump.
Depending on the design, the shock absorber rod can either be connected to the inner race of the bearing, or fixed through a bushing and a rubber damper to the body.
In the first case, bearing wear will more significantly affect the controllability of the car, the settings for camber and castor angles, so it can be noticed even before knocks appear.
As already mentioned, the sealing of the assembly from road dirt and moisture leaves much to be desired. As all this accumulates in the bearing, it corrodes intensively and begins to make sounds of a different kind, reminiscent of creaking and crunching.
If such a detail is dismantled, then the picture will be characteristic - the cavity between the clips is occupied by rusty fragments of former balls or rollers.
Do-it-yourself front strut diagnostics
Checking a suspicious node is quite simple. With the car at a standstill, one hand is placed on the shock absorber rod with a nut protruding from the suspension cup, and the other hand is actively rocking the body. It is better even to carry out such an operation together, since the efforts are quite significant.
The hand on the top cup of the rod will easily feel extraneous sounds and vibrations, which serviceable parts should not have.
If the assistant turns the steering wheel from side to side, and your hands, while on the rack cup or spring coil, feel a knock, rattle (crunch), then things are bad with the bearings.
If the shock absorber rod of a particular car is not connected to the inner race, then it will be difficult to check the part in this way.
You will only have to focus on the sounds during movement and the results of partial disassembly of the suspension.
Instructions for replacing the thrust bearing on a VAZ car + video
As an example, we can consider the process of removing and installing a part from the rack of a front-wheel drive VAZ car.
Replacement with rack dismantling
It is easier to work on a removed rack, and the likelihood of errors is reduced accordingly. In addition, for beginners, the visibility of the process is especially important.
- The machine is lifted from the desired side with a jack and placed on a reliable stand. It is strictly undesirable to work only on a jack. The wheel is taken off.
- The steering rod is disconnected from the swing arm of the rack, for which the pin nut is unpinned, unscrewed a few turns, the conical connection is strained by the mount and a sharp blow is applied with a hammer to the side of the lug. Reception requires some training, but you can always use a puller.
- The two lower bolts of the steering knuckle are disconnected, and one of them is adjusting for setting the camber angle, so this adjustment will have to be done at the end of the work. Bolts tend to go sour, so a penetrating lubricant or even a torch may be required. Then they are replaced with new ones.
- By unscrewing the three cup nuts under the hood, you can remove the rack assembly from under the car.
- To replace the support, you must compress the spring. Screw ties are used or, in a car service, a special hydraulic device. After compression, the support is released, you can unscrew the shock absorber rod nut, remove the support and replace it with a new one, performing all the operations in reverse order.
It is most convenient to use impact wrenches, electric or pneumatic. Acting with ordinary keys can cause difficulties, although it is quite possible.
Replacement without removing the rack
If there is no desire to carry out camber adjustment operations, and there is confidence in one’s ability to work in conditions of limited access, then to replace the support, the rack can not be removed from the machine.
In this case, it is better to loosen the shock absorber rod nut in advance, while the car is on wheels and there is convenient access to the nut. It will be much easier to unscrew it later.
The steering rod is disconnected in the same way, and in order to be able to move the shock absorber as far down as possible, it is necessary to unscrew the stabilizer bar. After disconnecting the support from the body, it becomes possible to put the couplers on the spring and do all other operations, as described above.
At the same time, the adjusting bolts remain in place and the suspension angles do not change.
How to refurbish an old bearing and support
When it becomes possible to save a thousand or two on the purchase of spare parts, then folk art has no boundaries. Once upon a time, this was really justified, since spare parts were transported to order, and it was long and expensive.
Now there is a choice for every taste and budget, and parts are often sold at hourly availability.
However, sometimes the selective replacement of parts in the support is justified even now. The car can be rare and exotic, and the whole set can be unreasonably expensive. Then it is quite possible to disassemble the removed support assembly, more carefully defect it and replace only really worn parts.
Most often it is enough to replace only the bearing. Many companies allow this, the bearing has its own catalog number and can be purchased separately. Or choose the right size, this is also possible.
As a result, the restored support will serve for a long time and is no worse than a new one.
