Shock Absorbers Explained

shock absorbers

Shock absorbers are one of the greatest innovations in the automotive industry. They have proved to be highly useful when it comes to vehicle safety as well as for passengers. More importantly, the way your vehicle drives smoothly over bumps today is all the work of a shock absorber. So let’s get right into how the absorber does the job so perfectly!

What Are Shock Absorbers?

Beginning with the basics, a car damper, more commonly known as a shock absorber, is a hydraulic or mechanical device. The prime function of shock absorbers is to damp or absorb shock impulses. 

How does this happen? All the kinetic energy that a shock receives with an impulse is converted into another form of energy by the shock absorber, which is mainly heat energy that is then dissipated. 

The History of Shock Absorbers

Coming to a bit of a background check on shock absorbers, we can find their origin back in 1907. The Frenchman, Maurice Houdaille, invented the shock absorbers taking advantage of hydraulic fluid.

His motivation came mainly from vehicle manufacturers who wanted to prioritize passenger comfort and solve steering problems. One of the major causes of passenger discomfort and steering problems was the spring rebound from a shock. 

Despite the solutions available at the time, none of them was adequate enough to help improve the ride experience. It was at this point that the innovative shock absorber came to the rescue. It was mainly designed to dampen the up and down oscillations of the leaf springs on a shock. 

In the early days, the first shock absorbers were simply a bolt connecting two arms with a friction disk sitting in between them. You could adjust the resistance of the shock absorbers by loosening or tightening the bolt.

However, these early shock absorbers were not the epitome of durability. Instead, they were quite poor performers. Nevertheless, they proved to be a step in the right direction. 

Over the years, shock absorbers, alongside the rest of the suspension system, have evolved sophistically. All components and mechanics continue to change and improve. However, the basic functionality of shock absorbers has remained the same: dampening the spring rebound. 

Houdaille type shock absorbers
The Houdaille type of shock absorber used on early Fords was one of the greatest inventions in the car industry. Therefore, he spent the next 27 years perfecting and marketing his design.

What Do Shock Absorbers Do?

If you want a simple answer to the question, here it is:

Shock absorbers are designed as part of a suspension system to find the right balance between the stiffness and flexibility of the suspension. They absorb the suspension’s vertical shock energy, or the kinetic energy when a car hits a bump.

This kinetic energy is then transformed into heat energy in the shock absorber’s dissipating or damping process. If you are wondering where the energy from horizontal movements goes, then that is the job of a trackbar

Where Are the Shock Absorbers Located?

All four corners of your vehicle have a shock absorber each. This is vital because all four wheels on the vehicle experience simultaneous movements. As a result, since all wheels can experience varying movements, they need a separate car damper to absorb the energy. 

A typical shock absorber comes in a cylindrical shape. They are attached to the two axles of the vehicle. The springs of a shock go around the shock absorber. This complete device works as a single unit in a multi-unit suspension system

Working of Shock Absorbers 

Here is a typical diagram of a telescopic shock absorber. Let’s see how it works when the vehicle comes across a bump:

working of the inner telescopic shock absorber components
Perfectly engineered inside pattern to ensure a brilliant workflow and smooth ride of your vehicle.
  1. The lower eye of the absorber moves up, making the fluid flow from the lower side of the valve V1 to its upper side.
  2. The lack of enough space volume above valve V1 than the rod exerts pressure on the valve V2, resulting in a damping force due to the fluid pressure.
  3. As the lower eye moves down, the fluid flows from the upper side to the lower side of valve V1 and vice versa for valve V2 (lower to upper).

This is how the inner components of a shock absorber work to smooth out the ride experience and enhance passenger comfort. Together with the shock springs, the shock absorbers ensure the impact does not damage the suspension and give greater handling control to the driver. 

Types of Shock Absorbers

There are mainly six different types of shock absorbers, which include: 

  1. Hydraulic type shock absorbers
  2. Single-acting shock absorber
  3. Double-acting shock absorbers
  4. Lever-type shock absorber
  5. Friction shock absorber
  6. Telescopic type shock absorber

Hydraulic Type Shock Absorbers

The first on the list is a hydraulic type shock absorber which is found on all passenger cars. They force the hydraulic fluid through small holes and check valves to enhance the resistance to the spring action. 

hydraulic shock absorber
Hydraulic type shock absorber is the best option if you like a softer and smoother ride.

Telescopic Type Shock Absorber

A telescopic type shock absorber is categorized as a direct-acting shock absorber. Its mounting position lies between the frame and the axle. They can be either extended or compressed. 

Single Acting Shock Absorber

A single-acting shock absorber, on the other hand, simply offers one-way resistance. This resistance process takes place only on the spring rebound and not when it compresses. 

Double Acting Shock Absorber

A double-acting shock absorber, as the name suggests, offers double resistance. This means that if your vehicle has a double-acting shock absorber, it will offer resistance during spring rebounds as well as spring compressions. 

Lever Type Shock Absorber

A lever-type shock absorber is categorized as an indirect-acting shock absorber. The lever in the name comes from its design, as it is attached to the chassis with a bolt through a link and a lever.

The hydraulic fluid or oil in this type of shock absorber is forced through the valve with the aid of a double piston arrangement. The resistance force of a lever-type shock absorber improves as the speed of the vehicle increases. 

Friction Type Shock Absorber

Friction-type shock absorbers were popular in the early days of the device. However, they didn’t prove to be highly durable and efficient. As a result, their inefficient damping abilities made them go out of fashion to the extent of becoming obsolete. 

Further Categorization Of Shock Absorbers

Now that we know all the six types of shock absorbers, let’s see how they are categorized into twin-tube and monotube. 

Mono-tube Shock Absorber

The main difference between a monotube and a twin-tube shock absorber is that it is designed inside a single cylindrical tube. It is basically a high-pressure gas shock that has a pressure tube. You can find a working piston and a dividing piston inside the pressure tube. 

A monotube shock greatly helps with supporting the weight of the vehicle. It can be used either upside down or right-side up. The ability to support the weight of the vehicle comes from their high flexibility. 

It is important to note that there is no base valve in a monotube shock absorber. They contain high amounts of oil and are known to dissipate the converted shock energy much faster. 

working scheme of monotube and twin-tube shock absorbers components
Monotube shock absorbers outperform twin-tubes in terms of damping effectiveness and ride comfort. Indeed, they are often more expensive than twin-tube shocks. Yet, the advantages of implementing these shocks much outweigh the costs.

Twin Tube Shock Absorber

Shock absorbers that have both an inner and an outer cylinder are called twin-tube shock absorbers. Inside the inner circle, there is a piston rod attached to the piston valve alongside the oil.

Then there is the base valve that controls the flow of oil between the two chambers. The outer cylinder houses a low-pressure gas that is mainly responsible for absorbing vibrations. 

The piston rod moves in accordance with the up and down movement of the wheel. When this happens, the piston and base valve determine the speed of oil flowing back and forth to dampen the shock impulse. 

Twin-tube Gas Charged

Gas charged shock absorbers offer significant advantages over hydraulic shock absorbers.

You can find twin-tube gas-charged absorbers, which help reduce hydraulic fluid aeration. This happens when the oil and air mix together and produce foam. Since the foam is more easily compressible, it negatively impacts the performance of the absorbers. 

As a result, nitrogen gas is added to the reserve chamber (replaced with ambient air) of a twin-tube gas-charged absorber to ensure the oil and air don’t mix together. The pressurized gas forces the oil into the working chamber keeping it constantly full.

As a result of that, filling with gas provides a strengthening effect on the shock absorber, which improves the vehicle’s spring rate.

This smart invention drastically boosts the performance and allows the shock to produce a more predictable and faster response.

Coilover

The coilover twin-tube shock absorber is a gas-charged absorber that features a unique design. It is engineered inside a helical road spring that is used on both two-wheel and four-wheel vehicles.

However, coilovers are widely produced for double wishbone suspension type of systems, and you might also see them being part of the MacPherson struts too.

These inevitable suspension components are quite flexible and convenient, which means that the customer is able to play with their settings such as: ride height and dampening intensity.

In particular car suspension systems, the caster and camber angle can also be regulated, of course if the coilovers consist adjustable top mounts (mostly used for racing cars).

A typical coilover consist of a telescopic damper, coilover, top strut mount, lower mount, dust boot, damper piston, upper spring seat, locking and adjusting perch, and a bump stop.

coilover components
Coilover parts work in a harmony providing you and your passengers a smooth and flawless ride.

Positive Sensitive Damping

Alongside the two cylindrical designs and nitrogen gas, a positive, sensitive damping absorber also has a set of grooves attached to the pressure tube. The primary function of these grooves is to allow free movement of the piston during the mid-range of travel. 

As a result, the piston moves less freely on irregular surfaces, where the up and down movements occur more frequently. 

Acceleration Sensitive Damping

Some Twin-Tube shock absorbers also come with Acceleration Sensitive Damping (ADS) technology. It helps deliver better handling as well as enhance ride comfort. It automatically senses smooth and bumpy situations as well as individual obstacles on the road. 

Spool Valve

The spool valves are designed using a hollow cylindrical sleeve with a machined oil passage that is in contact with traditional flexible discs or shims. Spool valving can be used with monotube, twin-tube, and/or position-sensitive packaging and is agreeable with electronic controls.

If you are entirely familiar with all types of shock absorbers, you might want to check some of our model specific best shock absorbers recommendations or brand comparisons.

Advantages that Shock Absorbers Bring

Shock absorbers have revolutionized suspension systems. Over the years, further innovation has allowed car manufacturers to make the ride experience as smooth as possible. Here are some of the prime advantages of shock absorbers: 

benefits of shock absorbers
Shock absorbers are an essential component of vehicle suspension. The majority of automobiles feature one shock absorber for each of the four tires.

Enhanced Vehicle Life

Shock absorbers dissipate a significant amount of vibration and impulse. As a result, this greatly helps with reducing the amount of damage to the vehicle. More importantly, it also brings down maintenance costs. They basically take the hard blows so the vehicle can survive for a long time. 

Enhanced Performance and Control

Shock absorbers allow the vehicle to perform better and move at faster speeds. Together, all four shock absorbers help keep the vehicle balanced and in control at higher speeds.

Enhanced Comfort

Shock absorbers ensure that passengers have maximum comfort during a ride. Doing their job, the absorbers take all the big bumps and blows so that the passengers can feel them as little as possible. 

Enhanced Safety

Shock absorbers also enhance the safety of the vehicle. They help with predictable movements of the car. More importantly, shock absorbers tone down the impact on the suspension, preventing it from damage and resulting in a possible accident. 

Strut and Shock Absorber Comparison

People often use the terms shock and strut interchangeably. This is mainly because they don’t know the difference between the two. While it is true that a shock and a strut perform the same basic job in a vehicle, there is a structural difference. To begin with, a shock cannot be replaced with a strut and vice versa.

A vehicle can either have a strut on each wheel or a shock. You cannot change the vehicle suspension to support the other. The reason is that, whereas a strut is structurally incorporated into a vehicle, a shock is not.

Moreover, a strut works as a crucial component of the steering system as well. As a result, your car’s alignment is directly impacted by any change in the strut.

This is also why you have to get the alignment adjusted when getting a strut replacement. Lastly, struts cost more than shocks due to their dual function with the wheels and steering. You can find various brands of struts and shocks to choose from.  

struts vs shocks
Struts, on the other hand, have an impact on alignment angles. The camber and caster angles are adjusted directly on the strut. That is why they are substantially more expensive.

Do Shock Absorbers Require Any Maintenance?

Shock absorbers are constantly working to ensure a smooth and bump-free car ride. They frequently absorb and redistribute the shocks evenly throughout the vehicle at all times.

However, you can get them regularly checked, and oftentimes they go unchecked for months. But, this does not mean that you can not maintain them properly. The best way to go about the maintenance of shock absorbers is to drive the vehicle with care.

Don’t exceed the weight limit and avoid going at high speeds over big bumps. Moreover, make sure your tire pressure levels are well within the standard limit. 

Simply driving carefully can help maintain the shock absorbers for longer. If you feel any difference in performance, immediately get them checked to see what the issue is. If they need a repair or replacement, get it done right away before they damage other components or cause an accident. 

Most manufacturers recommend a replacement of shock absorbers between the 80,000 to 100,000 km range. Unless you are doing a lot of towing and hauling, for which you need heavy-duty shocks.

Moreover, it is also recommended to get a replacement for shock absorbers in pairs. For instance, getting the front two absorbers replaced at the same time to avoid any issues with performance. 

When Should Shock Absorbers Be Replaced?

Since you cannot visually see the shock absorbers in a vehicle, you can’t really tell their condition. However, you can look for symptoms and signs that indicate the poor condition of shock absorbers. These indicators include: 

  • Steering wheel vibration
  • Vehicle nosediving when brakes are applied
  • Vehicle not hugging the road on turns and bends
  • Bald patches on tires
  • Vehicle excessive bounces on rough surfaces
  • Excessive veering around in side winds
car nosedives while breaking due to failing shocks or struts
You have an issue with your shocks and/or struts if the front end jerks forward or nosedives, braking takes longer, or you bounce over bumps all the time.

These are some of the most common symptoms of bad shock absorbers. If you experience any of the above, make sure to get them checked. More importantly, shock absorbers tend to lose effectiveness after around three years. 

However, you still have to get them checked every time your vehicle goes for service. In case you notice any indication of worn-out shocks, get them dealt with right away for your safety.

Also, always try to go for the best-branded shocks, which come with their own benefits and drawbacks. 

The Dangers of Worn Shock Absorbers

Shock absorbers are vital to the safety of any vehicle. Damaged or worn-out shocks greatly impact the car’s performance and reduce your control over the vehicle. As a result, the vehicle becomes prone to accidents that can be dangerous. 

Worn-out shocks are also damaging to the tires. The uneven bouncing due to worn-out shocks leads to uneven wear and tear on the tires. This can even damage brand new tires. 

Lastly, the worst impact of worn-out shock absorbers is suffered by the suspension itself. This directly brings down the handling performance of the car and makes the ride an unpleasant experience. 

Should you replace shock absorbers DIY?

The simple answer is yes. There is no rocket science needed to replace shock absorbers. You can refer to our article on how to replace a shock absorber. Just follow the steps properly and you will be good to go. 

If you have the right tools and equipment, you can easily go through with the process. Therefore, it is better to not spend on the replacement cost and instead learn the easy process yourself. 

Shock absorber replacement is an easy and straightforward job that anyone could do. Keep in mind, the right toolset is required!

Things To Keep In Mind!

It is important that you do not rely on the factory-recommended repair or replacement date for shock absorbers. Your vehicle type and driving conditions rather determine its lifespan.

On the other hand, manufacturers recommend replacement dates based on standard conditions, which might not be the same for you. 

Moreover, don’t replace the whole shock if you experience vehicle sag. That is the job of the springs. Have a professional inspect the car if you can’t figure out where the problem lies.

More importantly, keep in mind that it is not the priority of every manufacturer to offer a robust shock-absorbing system. Some compromise on this based on price and their focus on other components.

There are plenty of cheap but durable shock absorber options on the market that will do the job perfectly. Quite often people are very skeptical about them, but if you are on a budget our team has your back!

The main advantage is that we own an aftermarket car parts shop, which gives us the ability to test out various versions of less costly shock absorber brands, as well as the pricier brands out there!

Have a close look and decide whatever suits your needs the most. I really hope that with this article you have expanded your car knowledge which will definitely be valuable in future purchasing decisions for your home car.

Let us know in the comments below if you have any questions about shock absorbers or in general. We are here to help!

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