Importance Of Car Suspensions, Vehicle Handling, And Suspension Design.

1 How Does A Suspension System Work?

What Does Car Suspension Do?

The function of a vehicle’s suspension system is to absorb shock and vibrations while driving over rough roads, potholes, and bumps. To understand how car suspension works, we have to look at the parts of a typical suspension system and understand them individually. The suspension system consists of two major components: springs and dampers (shock absorbers or struts).

Springs

The primary function of springs in a suspension system is to absorb the shock and prevent it from getting transferred to the car body. The most common type of spring used is a coil spring that expands and contracts according to the up and down motion of the wheels. Some heavy vehicles, like trucks, use leaf springs that are made from several layers of metal (called leaves). Furthermore, air springs are also used on some luxury vehicles that use cylindrical chambers or air bellows positioned between the car body and the wheels. The compressive quality of air allows these springs to absorb shocks and vibrations.

Dampers or Shock Absorbers

The spring of a suspension system will continue to expand, contract, and bounce at an uncontrollable rate without a damper. Therefore, the suspensions are built with springs and a shock absorber or damper. It is called a damper because it dampens the movement of the spring by slowing down the magnitude of the vibratory motions. A shock absorber or damper features a twin-tube design that consists of a piston and cylinder assembly fluid with hydraulic fluid. When the wheel moves over a bump, the piston moves inside the cylinder, allowing the hydraulic fluid to pass through tiny holes present in the piston itself. Since the holes are small, the fluid passes gradually, slowing down the motion of the piston and the shock absorber, which in turn slows down the spring.

We all know the suspension of our vehicle ‌offers us comfort by preventing the shock and vibrations from getting into the passenger cabin. This helps in making the driving experience comfortable and also prevents other components from getting damaged by sudden shocks. However, there’s another important function of the suspension that plays a critical role in the vehicle’s handling. It ensures the tire remains in contact with the road at all times. This allows the driver to steer, brake, and accelerate the car, providing the necessary traction.

2 How Does The Suspension System Affect Car Handling?

Now that you have understood what the suspension is, its components, and how they work. Let’s understand more about these components and how they can affect the handling and driveability of the vehicle.

Ride Comfort

The ride comfort of a vehicle can be affected by various factors, like high-frequency vibrations, body roll, pitch, body booming, etc. A vehicle is considered uncomfortable if it has high NVH (noise, vibrations, and harshness) levels, high body roll, and if the vehicle lurches or pitches during acceleration and braking. A vehicle with a low-quality or poorly damped suspension system will experience increased cycles of oscillations, making the car difficult to handle and uncomfortable. For example, the ride is considered comfortable if the frequency lies between 60 to 90 CPM (cycles per minute). A frequency of 120 to 150 CPM is considered uncomfortable, and the ride becomes harsh for occupants. Generally, an average sedan car has a natural frequency of 60 to 90 CPM while a sports car that uses stiffer suspensions has a frequency of 120 to 150 CPM. However, low frequencies are not always suitable because 30 to 50 CPM can induce motion sickness.

Therefore, the ride comfort of a vehicle significantly depends on the design of the suspension and damping of the shock absorbers. Finally, to produce a comfortable ride, the suspension and related components are properly isolated with rubber mountings to minimize high-frequency vibrations.

Tire Grip And Traction

The springs of the suspension system hold the weight of the vehicle and the mass supported by these springs is called the sprung mass. Unsprung mass is the mass located below the spring or between the spring and the road. Unsprung mass includes the weight of tires, brakes, linkages, and other components that move with the wheels. The sprung to unsprung weight ratio plays a big role in how the vehicle performs. Today, the weight of unsprung components normally lies between 13 to 15 percent of the total vehicle’s weight.

Earlier, vehicle manufacturers believed the role of the suspension system was to absorb bumps and offer a smooth ride. However, as time evolved, they realized suspensions also serve a big role in maintaining proper tire contact with the road. If the unsprung mass increases, a greater force is generated by the wheels and other components while driving over bumps and obstacles. This reduces the tire contact pressure and decreases adhesion. Whereas a greater sprung mass keeps the tires more firmly in contact with the ground. The sprung-to-unsprung weight ratio is important for light vehicles because they have comparatively less weight and less unsprung mass, which makes it tough for these vehicles to maintain a proper tire grip on the road.

Body Roll

The stiffness of the suspension springs also determines how the sprung mass will respond while driving. Luxury cars like Mercedes or Cadillac are designed to offer a smooth ride because they are equipped with softer springs. However, it can cause the car to squat and dive while accelerating and braking. This also causes increased body roll during cornering, which is less in cars with stiffer springs. Sports cars like Mazda Miata may not offer a soft ride like a Mercedes, but they have reduced body roll and can be driven aggressively around corners. This makes them perfect for race tracks and performance driving. Therefore, besides sprung and unsprung weight, the stiffness of the suspension springs also affects the handling and performance of the car. Springs and dampers (shock absorbers) work together and are designed with precision to ensure optimum comfort and handling.

A major sign of a failing suspension system is a diving or squatting vehicle. This also leads to body roll but to minimize its effects, vehicles are equipped with sway bars. Sway bars are important components of the vehicle’s suspension system that ensure the tires remain in contact with the road and prevent the vehicle from tipping over, ensuring safety.

3 Double-Wishbone Vs Macpherson Strut Suspension

The two types of suspensions that are used in almost all vehicles today are double wishbone and strut suspensions. Double wishbone suspension, also known as double A-arm suspension, features two control arms (upper and lower). Each control arm or wishbone is attached to the frame with two bushings and the wheel via a ball joint. A shock absorber with a coil spring is mounted between these control arms to absorb vibrations and shocks. Whereas a MacPherson strut combines a shock absorber and a coil into one unit and is connected to the steering knuckle directly. This makes the suspension system very light and compact. Mostly used on vehicles with one control arm, MacPherson struts are very common in front-wheel-drive passenger cars. In comparison, the double-wishbone suspension allows more camber control (wheels tilting in or out) and helps to minimize roll or sway, offering improved car handling. They are also preferred in race cars for better control during high-speed cornering. Furthermore, with a higher degree of movement of control arms, double wishbone suspensions possess better deflection capabilities, making them perfect for off-road vehicles.

4 How Tuning The Suspension Improves The Handling Of Vehicle

While designing the suspensions of a vehicle, the manufacturers target certain handling characteristics specific to that car. The performance and design of a suspension system for a passenger car are different compared to a sports car. However, after the engineers finish designing and a vehicle is complete, the suspensions can still be tuned for different driving styles. You can change various variables like tire size, coil springs, dampers, suspension adjustment, anti-roll bars, etc to suit your style. For example, the oversteer and understeer of the vehicle can be controlled by attaching an anti-roll bar or stabilizer bar at the front or rear of the vehicle. Moreover, if your vehicle has two sway bars, one each in front and rear, you can use a thicker and stiffer sway bar to achieve more cornering force. Changing the tire and wheel size also affects the cornering and steering capabilities of the vehicle. However, tuning the suspensions of your vehicle for the desired outcome is a technical and detailed procedure. If you want to tune your car’s suspensions for better performance, refer to our comprehensive suspension tuning guide.

5 Suspension Systems Designed For Specialized Applications

This article has talked about mainstream front and rear-wheel-drive cars until now. But there are other vehicles like hot rods, racing cars, and extreme off-road vehicles that are designed for specialized applications and have different suspension settings. Although the working principle of the suspension remains the same, they are designed to provide additional benefits. Since each of these vehicles is driven in different conditions, the suspensions ‌deliver different handling capabilities and have to be understood separately.

Baja Vehicles

If you are an off-road enthusiast, you must have heard about Baja bugs or Baja cars. Volkswagen Beetle used to be a favorite amongst off-road enthusiasts and the most preferred vehicle used for off-road driving due to its low center-of-gravity and engine placement over the rear axle. These cars were modified for harsh racing conditions in the deserts of Baja, California and the most significant modification was the suspensions of these vehicles. These cars feature torsion bars as standard equipment on the front and rear which were raised to accommodate off-road wheels. Later, the torsion bars were removed completely and replaced with coil-over systems. Coil-over suspension systems are still used today and they feature both spring and shock absorbers in one adjustable unit. As a result, they allowed a whopping 20 inches of wheel travel at each end, making these cars easy to handle on rough terrains.

Suspensions Of A Formula One Car

Formula one cars are the pinnacle of automotive innovation and technology. The lightweight body design, advanced aerodynamics, high-performance engines, and precisely tuned suspension system make these cars fast and performance-oriented. The suspension of an F1 car is different from a normal car because it is not designed for comfort. They use multi-link suspensions with a remote push and pull rod mechanism similar to a wishbone-type suspension system. The biggest challenge while designing the suspension of an F1 car is the load and pressure generated at high-speed corners. Furthermore, the suspension has to be light and thin enough to maintain aerodynamics. This balance between strength, lightness, and compactness is tough to achieve. The suspension and other parameters like camber and toe are also optimized for each track to control how the tire performs on the road. Therefore, for F1 racing, handling, tire grip, and traction is the most important aspect, and is controlled by altering the suspension components of the vehicle.

The above-mentioned examples tell us how important suspension systems are for the handling of the vehicle. Each type of application requires a unique suspension system and tuning. For heavy cars and vehicles, leaf springs and air suspensions are used. These vehicles have high sprung weight, which makes the suspension design easier and the car stable. However, these suspensions have their own disadvantages. Similarly, light cars with low sprung mass have a high inherent agility and handling precision. Therefore, they have a low center of gravity, wider rims, and independent suspensions to maintain a proper tire contact for better handling.

In a performance car, the task of a suspension system ultimately is to maximize the amount of tire contact. Since tires are the only part of the car that touches the road, everything in the chassis setup should ensure they offer maximum traction and high-speed stability. Suspensions are even more important for off-road vehicles if you love to travel and camp in your 4×4 truck. When choosing the best 4×4 suspension system for your truck, it is important to consider factors like weight capacity and 4WD flex to ensure better off-roading capabilities.

If you lower your car and modify or tune your suspension system, there are three factors to consider: road isolation, roadholding, and cornering. A good suspension system isolates the road noises, reducing vibration in the cabin. It maintains proper tire contact with the ground so the vehicle can brake, steer and accelerate efficiently. Finally, the suspensions minimize body roll and transfer the weight of the car to ensure the car corners properly. This guide helps you not only in understanding how the suspension system affects the handling of the vehicle, but also gets you acquainted with the important factors to keep in mind while changing or purchasing a new suspension.

6 FAQs

What is Car Handling?

Car handling refers to the way a car responds and reacts to the inputs of a driver, as well as how it moves along a track or road. It is commonly judged by how a vehicle performs particularly during cornering, acceleration, and braking as well as on the vehicle’s directional stability when moving in steady state condition. Handling is an important aspect of a car’s performance, as it affects both the vehicle’s safety and its ability to perform in auto racing.

What are Car Dampers?

Dampers, also known as shock absorbers or suspension dampers, are automotive suspension components that reduce the severity of shocks, prevent body roll, and help the vehicle maintain stability. They are composed of hollow tubes filled with oil and a piston that moves through the oil to create a damping force. The damper is fixed to the car body or frame, and a pivoted lever extends from it to the axle. Some cars have dampers that contain both oil and gas, which act more efficiently than oil-filled dampers.

A Suspension System Keeps the Car Stable During What?

A suspension system is a system of tires, tire air, springs, shock absorbers, and linkages that connects a vehicle to its wheels and allows relative movement between the two. The suspension system must support both road holding/handling and ride quality, which is at odds with each other. Tuning of suspensions is all about finding the right compromise. It is important that the suspension keeps the road wheel in contact with the road surface as much as possible, as any road or ground forces acting on the vehicle will do so through the contact patches of the tires. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear and tear.

The suspension system keeps the car stable during driving on uneven roads, bumps, and potholes. It helps ensure you drive safely and smoothly by absorbing the energy of various road bumps and other kinetic shocks. The suspension system also helps your tires stay in contact with the road by increasing tire friction.