Car Suspension System (Suspension): Structure, Principles and Classification

Car suspension system is the structure that connects the vehicle body to the wheels, helping to absorb shock, maintain traction and stabilize the vehicle body, thereby improving smoothness, safety and durability of components. This is a key component that ensures the vehicle operates effectively on many types of terrain.

According to the JD Power 2023 Automotive Customer Satisfaction Index report, when the suspension operates smoothly and steadily, driver and passenger satisfaction increases by an average of 38%, while significantly reducing fatigue on long trips.

The structure of a car's suspension system includes: elastic parts, shock absorbers, steering mechanisms and auxiliary parts, which work together to absorb vibrations and keep the wheels on the road. 

In terms of operating principles, the system uses elastic components (springs, leaf springs, compressed air) combined with shock absorbers (shock absorbers) to eliminate vibrations when encountering obstacles, helping the vehicle stabilize quickly and reduce the risk of losing control.

There are three main types: dependent suspension, independent suspension and modern suspension. Choosing the right type directly affects performance and driving experience.

To keep the suspension system optimal, it is necessary to recognize signs of damage and perform regular maintenance according to the manufacturer's recommendations, avoiding widespread damage and costly repairs.

Learn more about car suspension systems in the article below.

What is a Car Suspension System? Why is a Suspension System Needed on a Car?

The car suspension system is the part that connects the car body to the wheels, helping to absorb shock, maintain road grip and stabilize the car body, thereby improving the smoothness, safety and durability of mechanical parts. This is a key factor to ensure the car operates effectively in many different road conditions.

Why do we need suspension system on car?

The suspension system acts as a “shield” between the chassis and the road surface, helping the vehicle operate more smoothly, safely and durably. Specifically:

• Absorbs shock from the road surface: Reduces vibrations transmitted from the wheels to the chassis, making passengers more comfortable. According to ISO 2631, whole-body vibrations exceeding 0,5 m/s² in the 4–8 Hz frequency range can cause muscle fatigue and reduce work performance.
• Keeps the wheel in constant contact with the road surface: Ensures traction, maintains acceleration, braking and safe cornering, and avoids the wheel lifting off the road when going quickly over bumps.
  
• Increase the life of other parts: Limits impacts that cause deformation of the vehicle frame, rapid wear of the steering and braking systems; protects parts such as steering tie rods, hub bearings, and brake discs.
• Support control capabilities: Combined with the steering and braking system to keep the vehicle balanced when braking suddenly or steering quickly, reducing the risk of losing control at high speeds.

Research by SAE International (2021) shows that trucks and SUVs using heavy-duty dependent suspensions have 15–25% longer mechanical component life than vehicles without regular maintenance.

Structure of Suspension System on Car

The car suspension system consists of many components that work together to absorb vibrations and keep the wheels on the road. The main components include elastic components, shock absorbers, steering mechanisms and auxiliary components.

1. Elastic part

This is the “heart” of the suspension system, responsible for absorbing impact force from the road surface and reducing vibration transmitted to the vehicle body. There are many types, each with its own characteristics, advantages, disadvantages and applications:

2. Shock absorber

If the elastic part is like a "cushion", the shock absorber is the "brake", whose task is to dampen the remaining oscillation of the spring so that the vehicle can quickly stabilize.

• Working principle: Use the resistance of hydraulic oil or compressed air to convert vibration energy into heat, helping the vibration to die out quickly.
• Common types:
• Hydraulic – pneumatic fork: Combining hydraulic oil and compressed air, providing high smoothness, often used on high-end cars.
• Dual hydraulic fork: There is a slave cylinder to distribute pressure, helping the fork not to be "stiff" when compressed quickly, suitable for bad road conditions.

According to a report by Automotive Engineering (2021), dual-type hydraulic shock absorbers help reduce 15–25% of excess vibration after the wheel passes through a pothole, increasing vehicle body stability.

3. Directional mechanism

It is a system of connecting rods, A-arms, tie rods and joints. They direct the movement of the wheel, ensure the wheel moves in the correct trajectory and withstand the impact force from the road surface on the vehicle frame.

• Link rod: Maintains the distance and relative position between parts.
• A-arm: Holds the camber and caster angles of the wheel in place.
• Rods and ball joints: Allow parts to rotate and bend flexibly according to suspension movements.

4. Auxiliary details

In addition to the main components, the suspension system is also equipped with many auxiliary details to increase stability, reduce vibration and protect the structure when the vehicle is operating, including:

• Stabilizer bar: Reduces the side tilt of the vehicle body when cornering sharply.
• Shock absorbers and shock absorbers: Prevent direct transmission of vibration from the suspension system to the frame and cockpit.
• Travel stop: Limits the compression travel of the suspension, avoiding damage during strong impacts.

Research by Continental Automotive (2020) shows that stabilizer bars reduce lateral tilt by 30–35% during hard cornering, improving vehicle stability and safety.

How Car Suspension System Works

The operating principle of the car suspension system is to absorb and eliminate vibrations when the car encounters obstacles, through the coordination between elastic parts (springs, leaf springs, compressed air) and shock absorbers (shock absorbers). This mechanism helps the car operate smoothly, stabilize quickly, maintain traction and limit the risk of losing control or overturning.

1. Principle of absorbing and eliminating vibrations

Think about it: when your car goes over a pothole or speed bump, the wheels will bounce up or down. Without a suspension system, all that shock would be transmitted directly to the frame and passengers, and could easily damage the car.

The suspension system works in 3 steps:

Step 1 – Absorb the impact

• Springs, leaf springs or airbags compress when the wheel hits an obstacle.
• They act as “cushions”, absorbing force and avoiding transmitting it intact to the car body.

Step 2 – Restore position

• After overcoming the obstacle, the spring wants to expand to return to its original shape.
• If there were only springs, the car would bounce up and down a lot like you were sitting on a trampoline.

Step 3 – Quench the Oscillations

• The shock absorber (shock absorber) will resist the movement of the spring, converting the excess energy into heat in the oil.
• Thanks to this, the car quickly stabilizes and no longer "bounces" continuously.

According to SAE International (2022), the combination of springs and shock absorbers helps the vehicle stabilize 40% faster after the initial shock than using springs alone.

2. Relationship between elastic part and shock absorber

Elastic parts (springs, leaf springs, pneumatics) help the car to be smoother when encountering initial shocks. Shock absorbers (shock absorbers) control the subsequent vibrations, helping the car to stabilize quickly.

• If the spring is soft but the shock absorber is weak → the car is bouncy and prone to motion sickness.
• If the spring is too stiff and the shock absorber is too strong → the car is bumpy and uncomfortable.

Car manufacturers have to calculate and test many times to find the "balance point" suitable for each type of car.

3. Impact of suspension system on road grip and vehicle stability

The suspension system not only provides comfort, but also directly affects road grip and vehicle stability in all driving situations.

• Helps the wheels stay on the road, even on bad roads. If the wheels lose contact, the car will lose traction and braking power immediately.
• Reduces side tilt when cornering, reduces nose-dive when braking hard, and reduces “tail kick” when accelerating.
• Reduce the risk of rollover, especially important with SUVs or trucks with high centers of gravity.

According to NHTSA (USA) 2022 statistics, improvements to the independent suspension system on SUVs have helped reduce 24% of unilateral rollovers compared to previous dependent suspension designs.

Classification of Suspension Systems on Cars

Car suspension systems are divided into dependent, independent and modern, each with its own structure, advantages - disadvantages and applications. From the simple structure, good load-bearing capacity of dependent suspension to the smoothness, stability of independent suspension and intelligent adjustment of modern suspension, the right choice will determine the performance and driving experience.

1. Dependent suspension system

This type of suspension has a simple structure, is durable and can withstand large loads, but has poor smoothness, and is often used on heavy vehicles.

Characteristics: Two wheels on the same bridge are connected by a rigid beam, meaning that when one wheel moves, the other wheel is also affected.

Advantage:

• Simple structure, very durable.
• High load capacity, suitable for heavy duty vehicles.
• Easy to maintain, low repair costs.

Disadvantages:

• Less smoothness due to vibrations transmitted from one wheel to the other.
• Large weight, increases fuel consumption.

Application: Mainly on trucks, buses or heavy vehicles.

2. Independent suspension system

This type of suspension provides high comfort and stability during operation, but its structure is complex and maintenance costs are high, mainly appearing on cars and SUVs.

Characteristics: Each wheel is attached to the body of the vehicle through its own mechanism, moving independently of the opposite wheel.

Advantage:

• Smoother ride over potholes or bad roads.
• Increased traction because the oscillation of one wheel does not affect the other.
• Helps the car to be more stable and safe when cornering at high speed.

Disadvantages:

• Complex structure, many parts are easily worn.
• Higher production and maintenance costs.

Application: Commonly used on cars, SUVs and some sports cars.

Research by Automotive Engineering (2020) noted that cars using independent suspension have 25% more comfort and grip when going over potholes than those with dependent suspension.

3. Modern suspension system

Today, many car manufacturers apply new technology to improve performance and comfort:

Air Suspension:

• Use air bags instead of traditional springs.
  
• Ride height and suspension stiffness can be adjusted depending on load conditions or road type.
• Advantages: Extremely smooth, increased off-road capability.
• Disadvantages: High price, complex structure, requires careful maintenance.

Electronic Suspension (Adaptive/Active Suspension):

• Uses sensors and ECU to automatically adjust damping force in real time.
• Helps the car balance better when cornering, braking suddenly or accelerating.
• Enhance safety and driving feel.

Suspension System Maintenance and Service

Suspension maintenance and servicing helps ensure smooth, safe vehicle operation and prolongs component life. Drivers need to recognize early signs of damage, inspect and service regularly according to manufacturer recommendations to avoid widespread damage and high repair costs.

1. Signs of suspension problems

Before discussing maintenance, you need to recognize the signs of abnormality of the suspension system to handle it promptly, avoiding widespread damage. Some common symptoms include:

• The car shakes or vibrates more than usual.
• Steering wheel off-center or have to keep steering wheel off-center to go straight.
• Uneven tire wear, especially on one side.
• When braking, the front of the car dives sharply or the rear "lifts" abnormally.
• There is a strange noise from the chassis when going over potholes or speed bumps.

IIHS (2022) report shows that 70% of suspension-related problems are detected early through signs of uneven tire wear, vibration or misalignment, helping to avoid major repair costs.

2. Periodic inspection items

Regular inspections help detect problems early and prolong the life of your suspension system. Items to look out for include:

• Check condition of springs, shock absorbers, stabilizer bars, and rubber shock absorbers.
• Measure and adjust wheel alignment and angle.
• Check for oil leaks in the shock absorber.

3. Proactive maintenance steps

Regular maintenance not only maintains smooth operation but also ensures safe operation. Tasks that should be performed include:

• Clean and lubricate joints, tie rods and bearings.
• Replace shock absorber rubber when cracked or hardened.
• Tighten bolts and nuts on suspension system connections.

4. Manufacturer's recommendations

Following the manufacturer's instructions helps the suspension system operate optimally and last longer. Some common recommendations are:

• Check the entire system every 20.000–30.000 km.
• Replace shock absorbers when performance drops above 50%.
• Priority is given to using genuine spare parts or equivalent quality.

Frequently Asked Questions About Suspension Systems

1. What are the common damages to the suspension system on cars?

Common suspension failures include shock absorber oil leaks, worn or cracked shock absorber rubber, broken or deformed springs, loose linkages, and misalignment causing uneven tire wear.

2. Is the "clunk" noise from the chassis due to a damaged suspension system?

Yes, the cause could be loose bolts, worn tie rods, or damaged stabilizer bars, which should be checked immediately to avoid widespread damage.

3. How does a car's air suspension system work?

Air suspension system Uses air bags inflated by a compressor to replace steel springs, allowing adjustment of suspension height and stiffness according to load or road conditions; pressure typically ranges from 5–12 bar.

4. Does worn suspension increase fuel consumption?

Yes, because when shock absorbers or springs are bad, the vehicle loses stability and the tires have poor contact with the road surface, increasing rolling resistance and fuel consumption by 3–5%.

5. Should the suspension be checked before and after the trip?

Yes. Check your car during and after the trip helps ensure the suspension system is in good condition. Check first for fork oil leaks, broken springs or worn shock absorbers to prevent problems. Check second for damage caused by vibration, impact or overload, especially after a bad road or long trip.

This is also an important part of general car maintenance schedule to maintain optimum durability and performance.

6. Why is it necessary to perform dynamic wheel balancing of a car to protect the suspension system?

The importance of dynamic balancing of car wheels This helps the wheels rotate smoothly, limiting vibrations transmitted to the suspension system, thereby protecting the shock absorbers, springs and tie rods from premature wear. In addition, proper dynamic balancing also reduces the risk of uneven tire wear and maintains smoothness and stability when operating at high speeds.

7. Which address is reputable for checking and maintaining car suspension systems in HCM?

Thanh Phong Auto is one of the leading prestigious establishments in Ho Chi Minh City specializing in providing comprehensive inspection, maintenance, diagnosis and repair services for car suspension systems for many car lines from popular to high-end. 

Outstanding advantages:

• Experienced team of technicians: Over 10 years in the industry, knowledgeable about both traditional and modern suspension systems such as air suspension, electronic suspension.
  
• Specialized equipment: Using wheel alignment machine, shock absorber tester, electronic diagnostic equipment meeting international standards.
  
• Standard testing procedure: Includes checking springs, shock absorbers, stabilizer bars, measuring wheel camber and toe angle.
  
• Genuine spare parts: Providing components from reputable brands, ensuring correct technical specifications.
  
• Clear warranty: Warranty commitment for repaired items, helping customers feel secure in using.
  
• Transparent consulting: Only recommend replacement when absolutely necessary, helping to save maintenance costs.

If you want your car to always run smoothly, stably and safely on every journey, come to Thanh Phong Auto to have your suspension system checked and maintained by a team of professional technicians, modern equipment and standard procedures. Contact us today to schedule an appointment and receive a free consultation!