- What are the functions of the suspension system?
- What are the components of the car suspension?
- What components are used in the suspension of different types of cars
One of the main components of the car is its suspension. The car’s suspension parts are responsible for ensuring the wheels’ grip with the road, smoothing out all the unevenness of the road surface as much as possible, and making the movement comfortable and stable at high speed. Since the invention of the first automobile, the suspension system has undergone many improvements and today has become a high-tech mechanism in vehicle design.
A Brief History of the Suspension
The history of the suspension begins from the days of horse carriages when the system for attaching the wheels to the carriage cab was the most elementary and did not have any shock-absorbing mechanisms. When driving on uneven roads, the passengers of such a crew were shaking violently. In the struggle for comfort, engineers began to come up with designs that mitigated the vibrations of the cab.
Elliptical springs became the first devices performing shock-absorbing functions. Over time, the spring mechanism began to be used on cars. By that time, the springs were already semi-elliptical, and they were installed transversely, which turned out to be not the best solution for the car because there were problems with its handling, even at low speeds. To solve this problem, manufacturers began to install springs longitudinally on each wheel separately.
Today, automotive technology has made great strides. Designers have developed various types of suspensions, and each type has certain features that affect not only the car’s handling but the comfort of people when travelling.
Despite the variety of designs, any suspension option should perform the main functions:
- Damping vibrations, as well as strong shocks that occur when driving on uneven surfaces.
- Ensuring maximum grip of the wheel with the road surface and eliminating the role of the car body during cornering.
- Improving vehicle handling by keeping the wheel in a given position.
A rigid suspension type is used for the car to be as stable as possible on the road during dynamic driving. This suspension type provides the car with good handling at high speeds, eliminates body roll when cornering, and responds instantly to the driver’s actions.
Despite all the advantages of a rigid suspension, passenger comfort during the trip cannot be satisfactory. Due to the rigidity, the ability to smooth out body vibrations is reduced. For normal driving, many passenger cars are fitted with a soft suspension. The car’s handling decreases, but the trip becomes much more comfortable, a more important parameter for an ordinary motorist.
Some car manufacturers produce vehicles with adjustable suspension stiffness. This function is provided due to the ability to adjust the spring tension of the shock absorber struts.
Suspension Travel
In addition to varying stiffness, the suspension can have varying degrees of travel. The distance between the wheel’s position when the springs are maximally compressed and the point in the maximally suspended state is called suspension travel. The increased travel helps the vehicle overcome obstacles on the road without the risk of the wheel hanging and the strut hitting the stopper.
The main components of the car suspension
Any suspension consists of several basic components:
- Tires. This is the first step in the road surface smoothing system. Having a certain degree of elasticity, the tire can damp a small amount of vibration during movement. In the event of a malfunction in the tire suspension, the wheels can act as a malfunction indicator, as the tire life in such a situation is rapidly reduced, and uneven wear occurs.
- Basic elastic components. The elastic components of the car suspension include springs, leaf springs and torsion bars. The purpose of these components is to provide an elastic connection between the body and the road surface. The entire load of the car falls on the springs, and due to their elasticity, the body is kept at a certain height. During operation and large overloads, the metal of the elastic elements wears out, due to which their rigidity changes. Such changes negatively affect the suspension’s overall performance—the angle of the wheels changes, the ground clearance decreases, the carrying capacity decreases. Sagging the body in an unloaded state is the main signal about the need to replace the springs.
- Additional elastic components. Additional elastic components include compression buffers. Their use is necessary to damp high-frequency vibrations and vibrations generated in the contact of metal elements. Thanks to such elastic elements, the service life of the remaining suspension components are significantly increased. It is imperative to monitor their good condition and replace worn-out parts in time.
- Guiding devices. The main task of the guiding devices is to ensure the movement of the wheel in the specified plane. Thanks to the system of levers, in the process of driving on an uneven surface, the wheel moves in a vertical direction while maintaining a perpendicular position relative to the road surface. Any irregularities in the guide elements will lead to rapid and uneven wear of the wheel tire and other suspension elements.
- Damping component. A shock absorber is a component of the damping device. The use of shock absorbers in the suspension system solves problems such as the body’s vibration when driving on uneven roads and smoothing vibrations on other elements of the car’s suspension. Thanks to the damping function, constant contact of the wheel with the road is ensured, the car becomes more stable when driving.
- Anti-roll bar. When cornering at speed, the anti-roll bar prevents the vehicle from rolling. When making a turning manoeuvre, the wheels of one side of the car begin to detach from the road, leading to the vehicle overturning. At this moment, a voltage is created on the stabilizer, which seeks to return the rising edge of the car to its place.
- Fastening elements for individual parts. The fastening elements include ball joints, silent blocks and bolted joints that connect the rest of the car’s suspension elements.
Front suspension parts of a car:
- Wheel bearing.
- Hub cap.
- Adjusting nut.
- Washer.
- Swivel pin trunnion.
- Wheel hub.
- Stuffing box.
- Brake disk.
- Rounded fist.
- Upper suspension arm.
- Upper support bearing housing.
- Compression stroke buffer.
- The axle of the upper suspension arm.
- Stabilizer bar mounting bracket.
- Stabilizer bar cushion.
- Stabilizer link.
- The axle of the lower arm.
- Stabilizer link cushion.
- Suspension spring.
- Shock absorber rod mounting clip.
- Shock absorber.
- Lower support bearing housing.
- Lower suspension arm.
What components does the suspension of different types of cars consist of?
2. McPherson suspension
The McPherson suspension is fitted to many vehicles and applies to both the front and rear axles. The only difference is that the front axle has the ability to turn the wheel. The wheel hub is attached to the lower arm with a ball bearing and the shock absorber strut. The strut rod is attached to the base of the car body through a thrust bearing, which allows the wheel to turn freely.
Both levers are connected by a transverse link, which is attached to the underbody through rubber bushings and contributes to the car’s stability on the road. There is no lower arm in the suspension structure on the rear axle, and the hub is fixed using transverse and longitudinal rods.
Advantages of McPherson Suspension:
- the simplicity of design;
- compact size;
- the high degree of reliability;
- relatively low price of the mechanism itself and the cost of maintenance.
Disadvantages of McPherson suspension:
- lack of ease of management.
The McPherson front suspension also features a shock absorber as a guide element, which saves on parts. The diameter of the stem of such shock absorbers is noticeably larger than that of others. Springs are most often used as elastic elements.
The springs are installed at a special angle concerning the axis of the shock absorber rod, which reduces a load of bending forces on the rod. The anti-roll bar is usually made from a curved round bar connected to the arms or A-pillars at both ends.
The main function of the stabilizer is to eliminate the role of the car when cornering at speed. The transverse stabilizer is fixed to the lower part of the car body utilizing intermediate supports. The stress arising in the corner in its structure tends to balance the load between the wheels.
The ability to turn the wheel is realized by a ball joint that connects the lower arm to the steering knuckle.
Double wishbone front suspension
A feature of the double-wishbone suspension design is a second trailing arm, which is designed for the upper mounting of the wheel hub. The design of such a suspension is more complex, but at the same time, has several advantages over a single-link system and can also be used on both the front and rear axles. Driving with this type of suspension becomes easier.
The main advantages of the double-wishbone suspension:
- due to design features, it is possible to lower the hood line;
- improved characteristics of changing the angles of installation of the wheelbase;
- extensive layout options.
The disadvantages of this type of suspension include:
- the weight of the structure has been increased due to a large number of parts, as well as its dimensions;
the more complex and expensive process of maintenance and repair; - the use of reinforced ball bearings and rubber-metal hinges since the connection points of the levers with other structural parts are subject to increased stress.
3. Pneumatic suspension
Air suspension is most often used in premium cars. Pneumatic suspension elements of a passenger car are powered by compressed air, making it possible to exclude the main elastic elements from the structure. Because air is used in the system instead of springs, the work of such an agenda is characterized by increased smoothness, and it becomes possible to adjust the height of the car body relative to the road.
4. Hydraulic suspension
A feature of the hydraulic suspension in the presence of a closed oil system connected to the shock absorbers. With the help of an oil pump, excess pressure is generated in the hydraulic circuit, which makes it possible to adjust the elasticity of the suspension, as well as the height of the body relative to the road surface. In conjunction with the hydraulic suspension, an electronic adaptive system is often used, which automatically changes the characteristics of the suspension under different road conditions.
5. Sports (helical) independent suspension
The sports suspension is based on adjustable coil-overs. The stiffness of the struts is adjusted due to the presence of a thread in the area of the lower part of the spring. When the adjusting nut rotates, the spring is either compressed or relaxed, thus changing its rigidity and ground clearance.
6. Suspension push-rod and pull-rod
These types of suspension are not used in standard vehicle trims as they were developed exclusively for racing cars.
The basis of both suspension options is a double-wishbone system. However, unlike other types of suspension, they are located in the body of the car. Most of the movement load falls on an element called a pusher.
In the push-rod system, the push rod is loaded by compression.
The pull-rod suspension differs in the position of the pusher. When a load occurs, this element works in tension, making it possible to lower the vehicle’s centre of gravity. Such a solution makes it possible to increase the stability of the car. However, the efficiency of both types of suspension is practically at the same level.