Truck Suspension Systems Explained

Every system in a truck is important and plays a role in maintaining performance.

If you’d like to learn more, you can enroll in the Diesel Technology program at Universal Technical Institute, which lasts less than a year and teaches students how to diagnose and perform repairs on all sorts of diesel vehicles!^1,7

That includes skills needed to service truck suspension systems, which contribute to the handling of a vehicle and its stability while on the road. While the purpose of suspension for cars and trucks is the same, there are major distinctions between the two systems themselves.

To get a head start on your diesel technology know-how, keep reading! You’ll learn more about what truck suspensions are, how they work and more.

Why Truck Suspensions Are Important

When it comes to heavy-duty vehicles like work trucks, suspension systems play a critical role in supporting the different operations the vehicles perform.

Pickup truck suspension systems are responsible for supporting the load being hauled by the vehicle. Often, these vehicles carry large amounts of equipment or products, so the suspension needs to be durable and reliable enough to handle it.

Truck suspensions also are crucial for providing stability on the road. Since these vehicles are heavier and might also be carrying additional weight, the suspension must be able to help with handling uneven roads. The suspension also helps prevent trucks from tipping.

The suspension also needs to help cushion the ride so the cargo and equipment remains protected over bumps and other imperfections in the road. Cushioning the ride also helps improve driver comfort, which can help maintain safe and attentive driving.

The suspension allows the tires and axles of the truck to move independently from one another, instead of the axle being attached to the frame directly. This helps soften the impact to the vehicle and helps absorb the impact of cracks, bumps or dips in the road.

Read: What Is Steering Linkage?

Types of Truck Suspensions and How They Work

There are a few different heavy duty truck suspension types that can be used depending on the application the vehicle is handling:

Leaf Spring Suspension

A leaf spring suspension system is one of the earliest systems and features long, arched pieces of steel that flex when needed. The leaf spring system is attached to the frame and a shackle that moves, which allows the length of the spring to vary.

More leaf springs can be added to support more weight. Heavy-duty trucks or other diesel vehicles often feature multiple layers of leaf springs if they have this type of system.

Pictured here is a leaf spring suspension setup, which is the most common type of suspension system used on big-rig trucks:

Torsion Bar Suspension

Torsion bar suspensions feature a narrow steel tube attached to the wishbone of a vehicle that twists around its axis. The tube is also attached on one end to the chassis, and this end does not twist. If a wheel hits a bump, tension gets created when the tube twists. After a bump, the steel unwinds and pushes the wheel down again.

Coil Spring Suspension

A coil spring suspension is a common system that is found in the front and back of many vehicles and in the front of some trucks. These systems feature springs that are spiraled and allow for flexibility in the form of bending and twisting. They are the most versatile system.

Truck Rear Suspension

While the go-to move for a while was to install leaf suspension systems on the rear of pickup trucks, coil spring suspension systems installed on the rear of vehicles became popular when Dodge introduced them on their 2009 Ram 1500s. These systems combine a lot of weight-bearing capability with comfort.

Read: A Guide to Truck Classifications

Truck Suspension Parts

There are many parts at work in a truck suspension system that help contribute to a smooth and safe drive.

Leaf Springs

Leaf springs absorb the motion of the truck, reducing the intensity of shock impulses from the road. They’re made of multiple layers of metal, known as leaves, stacked upon each other. These metallic strips, which gradually decrease in length as they’re stacked up, bend and flex to absorb obstacles from the road.

Shock Absorbers

Shock absorbers help to control the movement of the truck's springs and suspension by dampening the motion of the springs. This helps the truck make smooth and controlled movements, reducing the probability of skidding or veering off path. They also improve how comfortable a ride is by absorbing the bumps and vibrations that usually come with uneven road surfaces.

Control Arms

Control arms, also known as "A arms," play an important role in keeping the wheels grounded, improving traction and allowing for more effective braking by keeping the wheels moving in a consistent linear rhythm, which can prevent excessive up and down movement. By promoting even tire contact with the road, you can help to reduce tire wear and extend the life of your vehicle's tires.

Read: How do Tractor AC Systems Work?

Improving Suspension for Trucks

Improving your truck's performance can involve different strategies, ranging from structural changes to regular maintenance. Here are some tips that can improve your truck's suspension system:

1. Upgrade Your Shocks: Upgrading to performance shocks can provide improved stability and control, especially when tackling off-road conditions or carrying heavy loads.
2. Invest in a Lift Kit: A lift kit raises your vehicle's height, providing better ground clearance and enhancing the suspension's ability to absorb bumps and shocks.
3. Install Larger Tires: Larger, wider tires can help in distributing the weight of the vehicle more evenly, which can result in better traction and improved handling – ultimately leading to enhanced suspension performance.
4. Regular Maintenance: Regular maintenance checks and immediate attention to any suspension issues can ensure optimal performance and includes: maintaining proper tire inflation, replacing worn-out parts and ensuring your suspension system is always in peak condition.
5. Add a Sway Bar: A sway bar can help reduce body roll when turning, providing a smoother, more stable ride. This is particularly useful for trucks that regularly experience sharp turns or high-speed cornering.

Read: Glow Plug: What Does a Coil Light Mean?

Signs of Wear on Truck Suspensions

There are several signs that can indicate wear and tear on a truck’s suspension system. Paying attention to these is important so you can catch issues early:

• Bumpy rides: Bumpy and shaky rides on the road can mean there’s damage to the struts or other parts of the suspension.
• Uneven tire wear: Suspension issues can cause uneven impact on your vehicle, causing irregular tire wear and tear.
• Rocking: Noticing your truck rocking forward, backward or sideways when stopping or turning can be a sign of a suspension that is unable to properly stabilize motion.
• Lowered vehicle: If you notice a sunken frame or your truck leaning to one side or the other when it’s parked, there could be damage to the suspension.
• Leaking oil: Finding leaking oil on the shocks of your truck can be an indicator they are worn or damaged and need to be replaced.
• Noisy steering: Grinding or creaking noises could be the result of worn-out bushings, ball joints, or other key suspension parts that require attention

Be sure to take your truck to a trained diesel technician who has the expertise to diagnose and repair suspension issues. This will ensure your vehicle is riding properly and that you remain safe on the road.

Read: How Do Diesel Hydraulic Brakes Work?

FAQs

1. What Are the Different Types of Suspension Systems Used in Semitrucks?

There are mainly two types of suspension systems used in semitrucks: leaf spring and air suspension.

2. What Are the Main Components of a Truck Suspension System?

The main components of a truck suspension system include springs, shock absorbers and control arms. These heavy-duty truck suspension parts work collectively to absorb road shocks and maintain vehicle stability.

3. Can You Explain the Function of Each Part in a Truck Suspension System?

The springs absorb the impact from the road, the shock absorbers reduce the springs' movement to prevent bouncing and the control arms link the vehicle's frame to the suspension system, helping to maintain wheel alignment.

4. How Do Truck Rear Suspensions Differ From Semitruck Front Suspension?

Semitruck front suspension focuses on steering control, while truck rear suspensions are designed for stability and load bearing.

5. How Does the Suspension System in Trucks Contribute to Overall Vehicle Performance?

The suspension system in trucks maintains performance by ensuring a smooth ride and vehicle stability, even while bearing heavy loads. It also impacts truck handling, especially when navigating uneven terrain.

6. What Are the Signs of a Worn-Out or Failing Semitruck Suspension System?

Signs of a failing semitruck suspension system include excessive bouncing, drifting or pulling during turns, uneven tire wear, noisy steering and a generally harsh or uncomfortable ride.

7. Can You Explain the Importance of Maintaining and Servicing the Suspension System in Trucks?

Maintaining and servicing the suspension system in trucks is crucial to ensure the vehicle's safety, performance and lifespan. Regular maintenance can identify potential issues early on, which can prevent costly repairs and ensure a comfortable and stable ride.

Read: How Does a Diesel Engine Work?

Train on Heavy-Duty Truck Suspension Systems at UTI

The Bureau of Labor Statistics (BLS) projects more than 24,000 estimated average annual diesel job openings in the United States, and you could train to become one of the professionals equipped to service heavy-duty suspensions and more.⁴³ The Diesel Technology program at Universal Technical Institute teaches students how to diagnose and perform repairs and train for a career as a diesel technician. Our Diesel Truck Steering & Suspension Systems course covers the basics of how suspension systems work and how they’re put together.

You can graduate in as little as 45 weeks with the hands-on experience necessary for an entry-level diesel mechanic career.⁷ Find out more about the program online or by calling an Admissions Representative at 1-800-834-7308!