Car suspension diagnostics: how to do it right and why

Suspension structure and main details

Everyone knows that the roads in we drive on are far from ideal. Cracks in the paved surface, pits and potholes cause a lot of complaints from motorists. In addition, more and more speed bumps are appearing. Car suspension dampens all bumps and road defects.

When a car travels on rough road surfaces, all bumps are transmitted in the form of vibrations to its body. The connecting link between the body and the wheels is the undercarriage of the engine. One of the tasks of the suspension is to dampen vibrations caused by roughnesses in the road surface. The design of the chassis is designed in such a way as to provide the ability to move the wheels relative to the body and change the direction of movement of the vehicle.

Car suspension is a complex unit that includes elements such as:

• Elastic metal parts (springs, springs, torsion bars) and non-metallic components (pneumatic, hydropneumatic, rubber). These elements take the load that occurs when the car overcomes the roughness of the road surface, and distribute it to the body.
• Extinguishing parts (shock absorbers). Chassis components with a hydraulic, pneumatic or hydropneumatic device dampen vibrations that are transmitted from elastic parts.
• Guide parts made in the form of various levers connect the body to the chassis and determine their possible movement relative to each other.
• Stabilizers providing lateral stability of the car (an elastic metal bar, which serves to connect the chassis with the body, as well as to protect against an increase in the roll of the car during driving).
• Wheel bearings (steering knuckles located on the front axle, which take the load from the wheels and transfer it to other elements of the chassis).
• Fasteners of components and components of the suspension, which ensure their connection between themselves and fastening to the body (bolts, composite silent blocks, ball bearings).

The operating principle of the chassis of the vehicle is based on the conversion of shock energy, which occurs when the wheel hits a variety of road bumps, into the movement of elastic parts. At the same time, the movement of such parts is mitigated by damping elements (shock absorbers), therefore the impact force acting on the car body is softened. This is how the smoothness of the car is maintained. You can get a more visual representation of the operation of suspension parts by watching a video demonstrating their interaction.

Suspension of different models of engines has a different degree of stiffness. With more tougher the driving efficiency increases, but driving comfort is significantly reduced. A softer suspension creates increased comfort for the driver, but adversely affects the handling of the car. The challenge for car manufacturers is to find the best combination of driveability, comfort and car safety.

Why do suspension diagnostics

With regular inspection and repair of the chassis, you will ensure yourself safe and comfortable driving on the road. What is a running gear? It includes a frame, wheels with tires, suspension front and rear. The system for mitigating shock during movement is under constant load. She takes all the blows from the roughness of the roads. In this regard, the suspension deteriorates faster if the driver is aggressive in driving, especially on poorly paved roads.

Why is it useful to carry out preventive suspension diagnostics? If problems and small wear are detected at the initial stage, it is easier to prevent more severe damage. You can reduce the cost of repairing you car if you make it a rule to regularly inspect the suspension.

• When you need a suspension diagnosis in a car.According to the recommendations of specialists, a car enthusiast should carry out a diagnostic of the suspension every 10,000–20,000 km or once every six months. It is better to do this before the onset of winter colds, in the spring or in preparation for a long trip by car.Even if your car was bought recently or already has a minimum mileage, inspection of the chassis must be regular. In the event of any suspicious noise, the owner of the car must ensure its diagnosis.There are common signs by which you can determine the danger of driving and the need for technical assistance: strange noises and buzzing, as well as other unusual sounds while the car is moving. Such signs should give the driver a signal of impending problems.

  If, even with light contacts with pits and other defects of the road surface, you notice unusual behavior of the car (it “pushes” to the side, a noticeable backlash of the steering wheel appears, etc.), urgently carry out a running diagnostics. It is unsafe to drive such a car, moreover, a faulty car is a threat to pedestrians and other drivers. There is a chance of losing control while driving.

  Before buying a car, it is recommended that you diagnose the suspension and its components.

  Car repair experts recommend regularly inspecting the suspension, but it is better to check the entire vehicle. In this case, you will not feel a significant difference in money, but save time and secure the operation of your car.

  Stages of initial diagnostics of a car: determining the level of suspension reliability, identifying any mechanical damage; checking shock absorbers for leaks, as well as springs for elasticity and serviceability; determination of steering operability and integrity of CV joints; determination of the degree of deterioration of brake discs and pads. With more extensive diagnostics, a computer check of the condition of the car is also carried out.

• How to find out the cause of the problem. The driver of the car can pay attention to the appearance of malfunctions of the suspension during the performance of various maneuvers. A knock, noise, drifts to the sides, an increase in the braking distance are the main symptoms of malfunctions that are easy to notice. The reasons for their occurrence may be different, but the specialist of the service station will provide you more accurate information. The wizard will also make the necessary adjustments and perform minor repairs if a suspension problem is detected.Please note: if you neglect visits to the service stations and do not carry out minor repairs and suspension diagnostics on time, you may find yourself in a situation where the car needs an already expensive repair. A car with a faulty undercarriage can cause road accidents.
• Is it possible to diagnose the chassis without the service station?There are several significant reasons why diagnosing a car suspension at home will not be effective. This procedure requires special expensive equipment, as well as knowledge and some experience in working with equipment. We recommend contacting a service center for assistance.Slight savings on running diagnostics are not advisable. If you do not find an existing problem, it can be much more expensive or cause an emergency on the road.
• Why do we need a planned diagnosis of the suspension, is it possible to do without it.Decide what a car suspension is. The undercarriage of the vehicle is a system of elements connecting the housing and wheels into a single unit. Hodovka has an important function. It provides comfortable (without shaking) movement, as well as road safety while riding.You can neglect the comfort of the car and reduce costs. However, you can not save on movement safety. That is, the reliability and full performance of the suspension must be observed at every moment of movement.Parts and mechanisms of the vehicle wear out over time and require replacement. Diagnostics of the suspension in a car service helps to determine the need for repair.

  Many motorists believe that the cost of maintaining the car includes only the purchase of fuel and payment for parking. A competent motorist should allocate a budget for planned diagnostics. This is a small amount, which in the future will help to save on repairs.

  You may be wondering, how does a routine inspection of the suspension help save money? Costs will be reduced due to the fact that you do not spend money on a full and urgent car repair when the chassis suddenly became unusable.

  It is the problems with the chassis while driving are the main causes of accidents on the roads. This can lead to major troubles. Basically, in an accident, the body and its components suffer. Such repairs are more expensive and last longer to repair minor breakdowns. After an accident, you may need towing services, polishing or painting the body, replacing vehicle components, etc.

  Running diagnostics are recommended at least once a year. However, the responsible motorist conducts such an inspection at least once every six months. Moreover, for a service such as suspension diagnostics, the price is quite low.

  When checking the vehicle , all components of the chassis are inspected: brake pads, discs and drums, bearings, the tightness of shock absorbers, springs, backlash in the steering tips are checked, the performance of the clutch is evaluated, and much more.

  Such a wide diagnosis of the chassis and all systems of the car helps to determine the technical condition of the vehicle and plan preventive repairs.

Suspension Diagnostics Options

There are three main options for diagnosing a car suspension:

Of course, in any of the above options, the suspension is diagnosed using the same methods. Such a procedure, with certain knowledge, can be carried out independently. However, if you are not attracting a specialist, you need to know for sure: what, where and how to inspect.

Diagnostics of a suspension on a vibration stand – what is it

Damage to the car’s suspension can cause serious trouble. Cars can go into a skid when cornering and provoke an accident. A malfunction of the chassis does not occur “out of the blue”. Its parts wear out gradually, and the degree of such wear can be detected during the diagnosis. As you know, diseases are easier to prevent than to cure. The same statement will be true with regard to suspension failures. That is why it is very important to periodically check.

The design of the vibration stand for diagnosing the suspension includes a swinging platform, which has special sensors connected to the computer. When the platform on which the car is installed swings, the sensors read information about the suspension deviations and transmit it to the computer program. After that, the system compares the received data with standard values.

Suspension computer diagnostics is a rather complicated process. The vibration of the platform on which the diagnosed car is installed is necessary in order to create such conditions for the running gear that would maximally coincide with the real processes that occur during driving along a difficult road. The platform creates oscillations in the range 0–25 Hz, which gradually increase. In this case, the dynamic weight of each wheel is measured. This indicator is compared with the standard.

With a working suspension, a lower value of dynamic or static weight will be observed. During the diagnosis, the front and rear axles are sequentially checked.

Diagnostics of the car suspension on a vibration stand allows you to check the operation of the following elements:

• silent blocks;
• shock absorbers;
• springs;
• leverage;
• brake pads;
• steering tips;
• wheel bearings;
• ball bearings;

These parts of the chassis take up the main load when the car is moving. The vibration stand allows you to create simulations, including lateral swing. Sometimes during rocking of the car, knocks that are not related to the suspension of the car may be heard. The stand will not be able to accurately indicate the cause of their appearance, but it will become an indicator of the presence of a malfunction and will start further testing of the vehicle.

Unreliable running gear test results on the stand can be obtained due to incorrectly inflated tires. The most common mistake of the master diagnosticians is related to the incorrectly selected vehicle modification. As a result, the computer will compare the results of the chassis test with the factory settings of another car model.

To get accurate results, the suspension diagnostics on the stand should be carried out only by experienced specialists.

How to check the suspension yourself

From the outside it may seem that the diagnosis of the suspension of a modern car is a complex process, for the implementation of which special knowledge and professional equipment are needed. But each driver can perform a simple inspection of the chassis of his car. How to do this, we will describe in this section.

• How to check the front suspension.Many car models feature McPherson standard front suspension. The most expensive structural elements of such a “hodovka” are struts and shock absorbers. From the point of view of the complexity of the replacement process, it is worth highlighting the silent blocks of the stabilizer and levers. The most affordable and easy to disassemble / install parts of the front suspension are ball bearings.Self-diagnosis of the front suspension should begin with an inspection of the anthers and rubber protection elements of the chassis parts. It is worth checking the silent blocks and ball bearings. You must also check the mounting bolts and steering tips. If parts with damaged anthers are identified, it will be necessary to replace such components.Carefully inspect all rubber suspension seals. There should be no visible mechanical damage. Then you need to inspect the parts that are attached to the body. This can be difficult due to poor visibility.

  Damage to the shock absorbers can be indicated by oil smudges. Most often, they appear even earlier than the sounds when the vehicle is swinging. If the vibrations of the car are not damped sufficiently effectively, then the shock absorbers are already too worn out and they need to be replaced urgently.

• Identify a malfunction by eye.Heavily worn car suspension springs sag, so to identify this malfunction, you need to carefully inspect the car, paying attention to its landing. If the body is lowered lower than usual – this may indicate a “fatigue” of the shock absorber springs. With such a malfunction, it is impossible to correctly adjust the wheel alignment.For the diagnosis of ball bearings, you will need a viewing hole, as well as a mount. Using the latter, you need to click on the silent blocks of the lower levers and check the possibility of moving them up and down. The serviceability of the part is indicated by the absence of backlash, as well as mechanical damage on the rubber surface.Checking the strut bearings is a simpler procedure. To do this, swing the car up and down. In case of bearing wear, play will be noticeable. Experts note that if these parts are worn out, the car will swing more than once after swinging up / down.
• Driving and in motion. A number of suspension malfunctions can be diagnosed in motion or when the car is stationary and you are driving. Turning the steering wheel from side to side, you will check the work of the steering rack. As a rule, the appearance of problems with this assembly is associated with wear on the guide sleeve.By turning the steering wheel from side to side, faults in the steering tips and rods can also be diagnosed. For this procedure, you will need the help of an assistant who will hold the rods and tips, checking for any backlash. If a gap is detected, defective parts must be replaced.The diagnosis of the hub bearing is carried out while the vehicle is moving. A worn bearing will rotate loudly and evenly when the wheel rotates. This sound will be heard even with good soundproofing of the passenger compartment. Another option for checking the condition of wheel bearings involves hanging the wheels on the jack. The hung wheel must be rotated by hand or rocked, applying force at the highest point to reveal play.

  If you decide to do the suspension diagnostics yourself, do not forget to check the external joints of equal angular speeds (CV joints). Faulty, they will make a crisp sound at sharp turns with acceleration.

• How to check the rear suspension.The main structural elements of the chassis relate to the front suspension, so it is not so difficult to make an independent diagnosis of the rear “hodovka” In most budget models of cars that use independent suspension, the most expensive element in the back of the “hodovka” are the racks. This part “walks” on average about 100,000 km.In addition to shock absorbers, in the rear of the independent suspension there are no other important parts that affect the technical condition of the chassis. The rear silent blocks practically do not fail, but it is worth checking their condition. A more complex device is characterized by a dependent suspension, but here, the most important elements are struts and bushings. True, in this case, the latter wear out faster.Diagnosis of the rear suspension is carried out along with checking the entire chassis during a test drive. Symptoms of its parts are extraneous sounds and excessive swaying of the car body. If during a ride on an uneven road a car sways not only up / down, but also to the sides, then this indicates the need for urgent repair. If such a behavior of the suspension was revealed when checking the car before buying, then the conclusion is that the previous owner did not monitor the condition of the car, and it is better not to buy it.

Suspension diagnostics: the experience of ordinary motorists