How to check car suspension spring

The question of how to check the spring is often interesting for car owners only when the car «sags» even with a little load, or even without it. However, such a check of the suspension springs should be done only when the first symptoms of their wear appear.

It is best to make a diagnosis in the car service center on a special stand, but the easiest way to check the condition of springs can be done in the garage with your own hands. You do not need a special tool, and the procedure is available to almost everyone.

Symptoms of Bad or Failing Suspension Springs

Check the condition of the car suspension springs should be checked at one of the following symptoms:

Noticeable vehicle sagging

1. It became noticeable that one side of the car «sagged» more than the other in the unloaded state (without cargo and passengers). You need to look at the same axle, that is, for example, compare the front left and front right springs. In such cases, most likely, the spring is sagging or completely broken (on the sagging side).
2. A metallic clang while driving on a rough road is a clear sign of a broken suspension spring. And the above mentioned clatter may be produced even when driving over small bumps or potholes. However, in this case it is worth checking the steering rack and ball joint as well. Metal clattering usually indicates that one of coil springs is partially or completely broken.
3. The car's low landing with a slight load. This problem is usually more common on the rear springs, and the wheels begin to scrape against the fenders, and the mudguards begin to touch the road surface. It is a very dangerous situation, because this way the tires are worn out in emergency mode, and one «wonderful» moment they can simply burst.
4. Strong vibration and jolting during the movement of the car. At that, the jolting increases as the speed of the car increases. As a rule, it is a sign that the spring has burst completely.
5. Reduced smoothness of motion. This can be noticed by comparing the operation of the car before the appearance of the problem and after. Usually the spring stops working normally and the car jumps or dives into a hole when passing an irregularity.
6. Considerable roll of the car body even at not sharp braking.

If at least one of the signs listed above appears, it makes sense to fulfill complex diagnostics of suspension, including spring of shock absorber check. And it is desirable to check not only on the side where the car sagged, but all the rest, too.

Check the springs of the front suspension if, for example, when crossing a «speed bump» in urban conditions (or similar obstacles) the front of the car drops down significantly, up to the fact that it scratches the pavement. This indicates that the springs are significantly weakened, and therefore need either to install additional spacers, or to replace them.

Causes of spring failure

There are five main reasons why rear and/or front springs fail in whole or in part.

• Metal fatigue and spring wear. This occurs naturally over time. Metal becomes softer and more malleable in service. And also when the coils collide, the springs rust and develop microcracks.
• Constant friction between the coils of a weakened or heavily loaded spring. For this reason, the spring stiffness decreases, and the surface of the coils themselves becomes not round, as it was originally, but has a worn-out plane. Accordingly, for this reason, the bar becomes thinner, and therefore the spring is weaker.
• Overloading the car and driving it in this condition at high speed over bumps or distances. Under such conditions, all suspension components suffer, including the springs.
• Corrosion of the metal of the springs. This is a very common reason why springs fail. Over time, the paint on their surface peels off, and water and road reagents do their job. If corrosion «ate» a layer of only 0.15 mm on a 10-mm spring wire, the cross-section of said wire decreases by as much as 6%!
• Installing the wrong spring. In particular, this can happen due to the wrong selection of the part. Another variant is a factory defect. It often happens that springs with different stiffnesses are placed in one package.

How to Tell If Your Coil Springs Are Bad

How to Check Your Suspension Coil Springs for Damage: video

To check the condition of the suspension spring of the car, it must first be dismounted from its seat, cleaned of dirt and rust. This will allow you to visually assess its condition, check for cracks, chips and other defects.

First of all it is necessary to check the spring for stiffness. However, before that, you need to find out what class it belongs to, as well as what kind of springs the manufacturer recommends to install.

All springs are divided into two main classes — A and B. Their differences are in stiffness and length. The length of the A-springs is up to 27.8 cm, and the length of the B-springs is over 27.8 cm. As for the color coding, it depends on the specific car brand and spring manufacturer.

Checking with the press

To determine the fatigue of the springs by compression, you need to know what stiffness it should be installed in a specified place, so as to know with what to compare the results obtained in the future. Thus, in garage conditions, the stiffness of the spring can be checked with the following tools:

Press test of the spring

• two square-shaped bars with a thickness of at least 1.2 cm and an area slightly larger than the area of the end face of the spring to be measured;
• floor scales;
• a manual press (operated by means of a threaded drive).

The algorithm of how to check your current coil springs durability in this case will be as follows:

• Using a floor scale, find out the combined mass of the two bars and the spring being measured.
• Set the floor scales on the lower platform of the press, set on them one of the previously prepared bars.
• Place the spring on the bar and place the second bar on top of it.
• When you actuate the press it is necessary to compress the spring.
• The value of compression (distance) and pressure must be selected in advance according to the documentation. Accordingly, there can be no specific recommendations.
• From the obtained value of force (in kilograms of force) you must subtract the previously measured total mass of bars and spring.

If the spring has compressed a certain distance with insufficient force, it is an indication that it has significantly weakened and it is desirable to replace it. However, the decision to replace it should also be made on the basis of a visual inspection, as well as information about how many miles the car has been driven.

In practice, however, this method is quite problematic, since the test requires a force of about 325 kilograms-force.

Theoretical calculations

The allowable geometric variation of a spring, as well as its stiffness, can still be calculated using the appropriate formulas. Thus, the geometric change is calculated as follows: X = F × L / C. Here X is the change in size of the spring, F is the applied force, L is the initial length of the spring, C is the coefficient of proportionality, a table value (depends on the coil radius of the spring, spring material, rod diameter).

Similarly, the spring stiffness is calculated by another formula — K = F / X. Here also F is the force, and X is the size of the compressed spring measured as a result of the experiment. The complexity of such calculations is due to the fact that it is necessary to know the coefficient of proportionality, and this information can be found only in the technical documentation.

Checking in the manual

Measuring ground clearance

In the technical documentation (manual) to any car there is a detailed description of the procedure for checking the clearance, and, in particular, the springs. Let's consider such diagnostics on the example of the popular car Toyota Camry. So, for this purpose, you must first measure four parameters:

• A — the distance (clearance) from the center of the measured front wheel to the surface on which the car is installed;
• B — the distance from the center of the bolt of the lowered suspension arm #2 of the measured front wheel;
• D — distance from the center of the center of the measured rear wheel to the ground (ground clearance);
• C — distance from the center of the longitudinal arm bolt of the corresponding measured rear wheel to the ground.

Then you need to find the difference between the values A and B, and C and D. Then compare with the minimum permissible values given in the table.

If the values received as a result of measurement will be lower than given in it, it is necessary to carry out additional diagnostics. It may be necessary to use additional spacers, or to replace the spring with a new one.

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For other car models, you can find a description of a similar procedure with the corresponding values in the technical documentation. As a rule, the check algorithm is identical or not much different (the measuring points may differ).

When checking the condition of the springs, you should also pay attention to the condition of the tire spacers under them. Over time they naturally wear out, respectively, in case of significant wear the tire spacers must be replaced with new ones. At the same time, it is important to consider their height in order to ensure the normal value of the car's clearance.

When do I need to replace the car suspension springs?

It makes sense to replace the springs in the following cases:

Obvious spring breakage

• Replacement along with a faulty shock absorber. Such replacement is due to the fact that if this element is out of order, it is likely that the spring is already significantly worn, and soon it will probably break. In addition, if the shock absorber is stiffer, and the spring is soft, it will affect the overall work of the suspension of the car.
• If the coils are clearly broken. If the spring is completely broken, then it must be replaced with a new one, and as soon as possible. Operating a car with such a breakage is potentially dangerous, since it has a deterioration in handling. In addition, other suspension elements suffer.
• A strong roll of the car to one side. However, in this case you need additional diagnostics of the spring, because this situation can occur when the shock absorber fails. In some cases (if the spring is still in a more or less normal condition and only weakened) the situation can be corrected with the help of tire spacers, which are installed in the cup, thereby aligning the clearance of the car.
• Significant corrosion. If visual inspection will reveal that corrosion processes «ate» a large layer of metal, even in a small area, it is better to replace such a spring, because there is a risk that it will break exactly in the place of the rust nidus.

Many car mechanics advise to replace springs on a car every 10 years of its operation. However, it depends, firstly, on the quality of the springs used, and secondly, on the mileage and conditions of car operation. Before making such a decision, it is better to additionally diagnose the condition of the parts installed on the car. Another recommendation is to change the springs at every second replacement of shock absorbers, i.e. every 80 to 100 thousand kilometers.

FAQ:

• How do I know if a spring has gone on my car?

  One side of your vehicle sagged or it has a low landing even at slight load. Also you can feel strong vibration during movement and visible body roll while the car is turning or braking.

• When should coil springs be checked?

  You should immediately check coil springs if you notice an abrupt car bouncing while driving over bumps.

• How long do suspension springs last?

  Coil suspension springs can last over 50 000 miles, but most manufacturers recommend to check and change them on mileage 40 000 — 50 000 miles.

• What noise does a broken coil spring make?

  In most cases broken springs make a rattling noise. Less often you will hear metallic knocking and clunking noises.