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Many people aren’t quite sure what parts make up a car’s suspension system, or even what its main job is. That’s understandable—after all, the suspension system is hidden from view during everyday driving. Yet it remains one of the most important systems in any vehicle. Since we’ve covered suspension basics in other articles, this time T.G.Q will dive into the key components that make up a vehicle’s suspension system.
What Is a Suspension System?
Simply put, a car’s suspension system is responsible for absorbing shocks from the road and controlling the position of the wheels. Its two main goals are to provide a comfortable ride for passengers and responsive handling for the driver. Suspension systems generally fall into two categories: rigid (dependent) suspension and independent suspension. Some components are shared between these systems, while others are unique. This article focuses on the most common parts found in both.
Springs
Springs sit between the wheel axle and the vehicle’s body frame. They support the vehicle’s weight, absorb vertical road impacts, protect the chassis, and help with handling.
Common Types: Coil Springs and Air Springs
In independent suspension systems, coil springs and air springs are the most common. Many modern cars combine springs and shock absorbers into a single unit called a coilover, saving space and freeing room for the cabin or other components.
Spring Stiffness and Performance
Spring stiffness is measured by the spring constant, or k-value. A higher k-value means a stiffer spring that requires more force to compress. Stiffer springs usually deliver sharper handling and greater load capacity, which is why sports cars have firmer springs than passenger cars—explaining their firmer ride.
Tuning Spring Characteristics
Coil spring performance can be adjusted by changing the number of coils, wire thickness, coil shape, and end design. Air springs vary stiffness by inflating or deflating the airbag. With heavier electric and hybrid vehicles becoming common—often weighing over 4,500 pounds—more automakers are adopting air springs for better overall performance, despite their higher cost compared to coil springs.
Shock Absorbers
While springs absorb shocks, they also cause the vehicle to bounce. Shock absorbers, or dampers, reduce this bouncing, keeping the ride smooth and stable.
Inside a shock absorber, a piston moves through oil in a sealed cylinder. Oil flows through tiny holes, creating resistance that slows motion. Adjusting these holes changes the damping force, balancing comfort and handling.
Modern Innovations
Many cars combine shock absorbers with coil springs into coilover units to save space. High-end models often feature electronic shock absorbers that adjust damping on the fly for different driving modes.
Common Misconceptions and Importance of Tuning
Shock absorbers don’t support the vehicle’s weight—that’s the springs’ job. Instead, they work together with springs to control vertical motion. Proper tuning between the two is crucial for ride quality and handling, making shock absorbers a popular yet challenging upgrade.
Stabilizer Bar and Stabilizer Link
When a car corners, inertia, center of gravity, and roll height cause the body to lean or roll. Excessive body roll can make passengers uncomfortable and impair handling. Independent suspension systems, which allow wheels and body to move freely, can sometimes increase this roll.
To combat this, engineers use a stabilizer bar (or anti-roll bar), typically a U-shaped metal rod. It connects the suspension on both sides of the vehicle via stabilizer links and bushings. The bar resists differences in wheel height between the left and right sides, reducing body roll during turns.
Stabilizer links are metal rods with ball joints at each end. These joints allow the stabilizer bar to pivot freely without bending under force. The stiffness of these joints is critical for proper interaction between the bar and wheels. While stabilizer bars rarely fail, stabilizer links generally last around 80,000 miles before needing replacement.
Control Arms
How exactly is the car body connected to the wheels, and why don’t the wheels wander? The answer lies in the control arms. One end of a control arm attaches to the car body (or subframe), while the other connects to the wheel knuckle. Control arms constrain the wheel’s movement within a specific range, maintaining alignment and stability.
Depending on the suspension design, each wheel can have between one and five control arms. They are usually made from steel or aluminum and come in various shapes—L, I, or V-shaped. Control arms feature ball joints on the wheel end to allow smooth steering and rubber bushings on the body end to absorb vibrations, preventing them from reaching the cabin and reducing stress on the chassis.
Bushings
The suspension system connects the body and wheels, but the body end usually requires less freedom of movement—primarily rotation. For this, manufacturers use bushings, typically made of rubber, which are cheaper and effectively absorb road vibrations.
To fine-tune comfort and handling, bushings often have grooves that vary stiffness depending on angle or force. Some advanced designs even inject fluid into the rubber to create hydraulic bushings, further improving ride quality. Recently, some automakers have experimented with electromagnetically controlled bushings that adjust stiffness electronically for an even more refined driving experience.
Knuckle
While not always classified as a suspension component, the knuckle is central to almost every suspension system. This metal part has multiple holes to attach ball joints, control arms, tie rods, and the wheel hub itself. The top usually connects to the shock absorber. It serves as the pivot point for steering and supports the wheel assembly.
Subframe
Like the knuckle, the subframe is not strictly part of the suspension but is essential. It acts as a mounting point for suspension components, the powertrain, and steering, connecting them to the vehicle’s main body via bolts. Independent suspension systems especially rely on subframes to hold everything securely.
Conclusion
This article aims to give you a clear understanding of the key components that make up a vehicle’s suspension system. While we focused mostly on independent suspension due to its prevalence and complexity, these components form the backbone of modern vehicle dynamics. Knowing how each part functions helps appreciate the engineering that keeps your ride smooth, safe, and enjoyable.
Reference
- T.G.Q R&D
