Automotive Shock Absorber
Source: http://performanceshock.com

Shock absorbers are critical vehicle parts. Despite that, many people do not understand them well.

Learn about shock absorbers in this article: their working principle, purpose, and how they differ from suspension struts. We will also answer popular questions about these suspension system components.

To start off, a brief explanation regarding shock absorber meaning.


Shock Absorber Definition

What is shock absorber in a car? Put simply, a vehicle shock absorber is a pump-like device that helps dampen the rebound movements of suspension springs.

It is one of the many parts of the suspension system of motor vehicles.

Shock absorbers are not structural suspension parts. They are independent components whose main purpose is to keep the wheels on the ground and ensure smooth rides.

There are other functions of these devices, as we will see later.

Shocks are placed in every corner of automobiles that use them. One part attaches to the chassis, the other the axle near the wheels.

A vehicle may have both front and rear shock absorbers. Often, the front wheel will have struts instead of front shock absorbers. Struts assist the steering system to function, of which the front wheels are part of.

The application of shock absorbers is not restricted to cars and trucks only. Every road vehicle can use them.

You will find the parts in construction machinery, tractors, and even motorcycles.

They improve the drivability of automobiles, riding comfort, and driving safety.

Motorcycle shock absorbers are placed on the fork of the wheel. They prevent excessive vibrations when riding in rough conditions. By controlling the vertical movements, the shock absorbers of motorcycles help to ensure comfortable and safe rides.

Motorcycle Shock Absorber
Source: www.ebay.com

Shock absorbers come in different sizes and designs. In its simplest form, the device consists of a piston attached to a rod, a tube filled with hydraulic fluid, and openings in the piston to control the movement of fluid from beyond the piston and vice versa. 

Hydraulic shock absorbers use oil. Other types use air as the compression fluid and are called ” air shock absorbers “. Shocks that use oil are the most common.

The use of pneumatic shock absorbers is rare. Although the types of fluids differ, the working principle of shocks remains more or less the same as you can see below.

Next, let us look at the work of a vehicle’s suspension shock absorber.


Functions of Shock Absorbers in a Car

What does a shock absorber do? The shock absorber purpose in a car is an essential one.

Vehicles encounter different road imperfections. It can be bumps, potholes, or any other irregularity. These can cause the vehicle to bounce uncontrollably and the tires to lose road grip.

That is where the shock absorber function comes in.

Car shock absorbers help to present the excessive bouncing caused by bumps. Shock absorbers on a car also help to keep the wheels on the ground.

The vehicle then steers effectively, offers reduced braking distance, and rides are comfortable.

Shock absorber on a car
Source: http://www.superstreetonline.com

The functions of shock absorber in a car, truck, and any other automobile can be summarized as:

  • Limit the movement of a vehicle’s body– By damping the oscillations of the chassis, shock absorbers of cars help control the vertical motion and sideways sway of the car body. It ensures quality rides where vehicle occupants do not feel every bump or pothole.

  • Ensure contact between the road and wheels- when driving on bumpy roads, the wheels bounce up and down. Tires then lose contact with the ground and the vehicle becomes difficult to control. Car shock absorbers help minimize the bouncing and improve steering and directional stability.

  • Stabilize rides- automotiveshock help to ensure transitioning from bumpy to even roads and vice versa does not produce noticeable differences. It improves the overall ride, regardless of the road conditions.

  • Reduce wear of the tires and parts of the chassis-when tires do not move up and down constantly, they wear evenly and at a reduced rate. Car shock absorbers also protect the suspension. Fewer and less severe movements mean minimal wear of the suspension components.

Despite their name, shock absorbers do not absorb “shock”. That is the work of suspension springs.

Instead, the primary function of shock absorbers is to damp the spring oscillations. It does so by slowing down the spring movements so a vehicle does not bounce up and down too many times.

As you can see, the shock absorber meaning does not match its name. A better world to call shock absorbers would be “dampers.” Actually, that is the other name of these devices.


Shock Absorber Working Principle

Internal structure of two common shock absorbers for cars and trucks
Source: http://iscsuspension-na.com

How does a shock absorber work? As mentioned earlier, car shocks are technically oil pumps. The shock absorber operation involves pumping hydraulic fluid from one chamber into another and vice versa.

Here is how a shock absorber works.

In its simplest form, a car or truck shock absorber consists of a piston inside a sealed pressure tube. The piston contains tiny holes (orifices) that only allow a small amount of oil to pass through. (The shock absorber oil is a type of viscous fluid).

When a vehicle hits a bump or any other road irregularity, the tires move upward.

The vertical movement compresses a spring, which then absorbs the shock and cushions the chassis. The compressed spring now possesses stored or potential energy.

The stored energy of the compressed spring must be released.

The spring does that by returning to its original length, an action that pushes the chassis upward.

Gravity then almost immediately pulls the chassis down, compressing the spring again.

In reality, the chassis would continue to bounce up and down until the spring loses all the stored energy. That would take a long time.

If the road is too bumpy, the vehicle would be almost unbearable to ride in. The wheels could even leave the ground and make the vehicle uncontrollable.

Suspension shock absorbers help to dissipate the energy of the compressed spring and limit the up and down movements.

Below is a diagram showing the internal working of a shock absorber.

The action described here is the hydraulic shock absorber working principle. Hydraulic shocks are the most common and found in virtually every motor vehicle today.

Diagram showing the working of a shock absorber
Source: http://www.bikedeals.in

Às we have seen, most shock absorbers feature a sealed tube and a piston that moves through the oil.

The piston is connected to the vehicle body so that it moves with the up and down movement of wheels and chassis.

The piston head contains small openings.

As it pushes through the hydraulic fluid in the pressure chamber, oil forces itself through the holes. The resulting resistance to the flow produces heat.

The energy of the compressed spring is, therefore, turned into thermal energy and dissipated through the shock absorber walls. It is the reason why shock absorbers feel warm, especially after driving on uneven roads.

Some shocks feature a gas chamber to prevent the hydraulic fluid from foaming. The gas is contained in a space at the end of the pressure tube.

An independent piston separates the gas from the oil. Gas filled shocks perform better in harsh driving situations, such as bumpy roads.


Shock Absorbers Vs. Struts

Shock Absorber vs Strut
Source: http://www.bestnetreview.com

When talking about shock absorbers, the word “struts” will usually come up. Some people even use the two words interchangeably.

But are shock absorbers and struts the same thing? The simple answer is NO. Car struts and shocks differ in many ways but mostly in design.

Here are the major differences between shock absorbers and struts.

  • Shock absorber and strut assemblies differ structurally. A strut combine a spring and shock absorber in one piece. Shock absorbers do not incorporate a spring, unless if it is the coil over shock.

    However, coil over shock absorbers should not be mistaken for struts.

  • Struts support the sprung weight of a vehicle, or the chassis, on a coil spring. Shocks do not carry any weight, whether sprung or unsprung. That means the operation of a shock is slightly different from how a strut works.

  • Shock absorbers are independent components of the suspension, and their purpose is to dampen spring oscillations. Struts form a structural part of the suspension.

  • Besides helping to limit the bouncing action of a vehicle body and wheels, struts also form part of a vehicle’s steering system. It is one of the reasons why you should align the wheels after replacing struts.

  • Because struts are also steering components, they are usually installed in the front axle on either side of the vehicle body.

    Some vehicles use shocks both in the front and rear wheels, others in the rear only. Mostly, it depends on the type of suspension.

  • Struts are used in suspensions that do not use upper control arms. Shock absorbers are found in vehicles that use both upper and lower control arms.

  • Struts are typically smaller than shocks. For that reason, they are usually installed in vehicles with short suspension travel.

A vehicle can only use a shock absorber or strut at each wheel and never both. Compared to struts, shock absorbers are easier and less costly to replace.

Along with the costs to change a strut also comes the safety issue.

The coil of a strut is usually compressed and could cause accidents if it came off unexpectedly.


Coil Spring and Shock Absorbers

Coil Spring and Shock Absorber
Source: http://www.ebay.co.uk

A vehicle coil spring, also known as ” suspension spring “, helps to absorb the shocks caused by bumps on the road.

It helps to make rides smooth and comfortable by cushioning the chassis.

But having a coil spring is not enough to make a vehicle comfortable or safe to ride in. Its cushioning action involves bouncing up and down, which presents another problem.

To absorb the spring oscillations and limit vertical movements of the vehicle body, a shock absorber is usually installed next to the spring.

The spring and shock absorber relationship is, therefore, a mutual one. Each depends on the other to perform its function effectively.


Common Questions About Shock Absorbers

Many people do not understand the shock absorber function or even the shock absorber working principle. They may even neglect these essential suspension parts and drive with worn shocks.

To help you understand the work of shock absorbers, we compiled a list of FAQs.

Question: How many shock absorbers are installed in a car?

Answer: Usually, there will be one shock at each wheel. Car front shock absorbers help to cushion the front axle.

They are responsible for preventing excessive diving during braking. Rear shock absorbers perform a similar function of limiting vertical oscillations.

Together with the suspension springs, rear shocks also prevent vehicle squats upon acceleration.  


Question: How long can car shock absorbers last?

Answer: It is difficult to give an exact figure since driving conditions and habits vary.

Usually, shocks will need replacing after 30 000-75 000 miles the average being 50 000 miles.

Most shock absorbers are designed to last a long time, up to 100 000 miles or more in gentle driving conditions.


Question: How often do you need to change shock absorbers?

Answer: As often as necessary. Worn shocks will show specific symptoms.

Often, the signs of shocks that require replacing are easy to detect.

Change degraded shocks as soon as it becomes apparent that they are no longer working properly.

If it is a long time since you changed your shocks (say 60 000 miles or more), consider installing new ones.

Check out our article about shock absorber troubleshooting and replacement.


Question: Can car shock absorbers be repaired?

Answer: Definitely yes. Shocks are designed to be serviceable.

You can actually replace individual shock absorber parts.

However, replacing excessively worn shocks is way better than fixing the problem. You will eventually need new ones, and the overall cost could be huge.


Conclusion

Shock absorbers help to keep the wheels of your car on the road. They also absorb spring oscillations and stabilize your vehicle when driving.

These are just a few of the shock absorber functions.

Understanding the working of these auto parts is essential. You will know when your car is not performing as it should due to worn shocks and take the necessary action on time.

The information contained in this article should help you ensure you have working shocks at all times.