What types of suspension do new cars use?
Hello everyone! Your favourite pretend engineer is back after a very long and uneventful summer holiday! Today, we will answer a question which is interesting, not only to us car enthusiasts, but also to the average person who is buying a car, and wants to know: what types of suspension do new cars use? Which one is good at what? Today we shall address all of these questions regarding car suspension.
Before we discuss the different types of suspension, let´s ask for a moment: why do cars need suspension anyway? There are multiple reasons:
1. Comfort and handling: car suspension absorbs all of the abnormalities of the surface the car is driving on, minimising the amount the car is disturbed and making sure that the car doesn´t veer excessively off course due to a bump.
2. Performance: the suspension also ensures that the tyre(arguably the most important part of a car) stays in contact with the road for as long as possible, and throughout a wide range of conditions. Therefore, a car that has the correct suspension setup for the application will be faster and safer.
Most popular types of suspension
Double wishbone suspension: This type of independent suspension (one wheel doesn´t affect the other when hitting a bump) was relatively rare in the early 20th century due to it´s cost and complexity, but nowadays is available on many high end comfort oriented cars. It consists of two wishbone shaped arms (one above the other) that connects the chassis to the wheels. These two arms pivot up and down from a centre axis, allowing the wheel vertical movement. This type of suspension also features a shock absorber and spring, which connects the bottom wishbone to the chassis.
The wishbones on this type of suspension are usually of unequal length (usually the top wishbone is shorter) to make sure that the wheel goes up and down as straight as possible, minimising camber change. This type of suspension is very versatile allowing engineers to optimise the suspension for comfort, sportiness, or even both at the same time!
This suspension is usually used on all four corners of more expensive cars; both comfort and performance cars.
McPherson suspension: This type of suspension is also independent, and consists of a single control arm (or wishbone) that connects to the bottom of the hub of the wheel. The bottom of the shock absorber is connect to the top of the wheel hub; and from the top to the chassis. It is usually found on the front of many cars, especially if they are front wheel drive.
The pros and cons of this type of suspension are:
Pros:
McPherson suspension is very cheap to make, is very simple and more compact than other types of suspension, allowing for smaller cars that aim to offer good ride and handling characteristics while lacking the space for a double wishbone suspension.
Cons:
This type of suspension is so simple, it doesn´t give engineers much room to improve it´s characteristics.
Due to the design, the wheel follows a curve when going up and down (camber change) and; due to the position of the shock absorbers, it usually raises the centre of gravity of cars fitted with this suspension.
Multi-link suspension: This suspension type is also independent. In fact, it´s really similar to double wishbone suspensions. The main difference is that multi-link suspensions use more than 3 lateral control arms and one or more longitudinal arms. All of these control arms connect to the wheel hub from one end, and to the chassis from the other. This suspension also uses a spring and shock absorber, but is located farther back, allowing more space for all of the control arms. These are a very popular rear suspension alternatives to double wishbones, especially rear wheel drive or all wheel drive cars. They can even be found on offroaders because it offers lots of suspension travel, which is very desirable when offroading.
The pros and cons of this type of suspension are:
Pros:
This suspension features most of the double wishbone´s pros, but without most of the drawbacks. This suspension allows engineers to optimise the design for the specific application, and is very light, allowing for this design to be implemented on many cars.
Cons:
When used as a front suspension setup, as the front wheels move as the driver turns the wheel, the suspensions geometry changes slightly; as the steering movement torques the arms, although the engineers design the suspension to allow this to happen without any real repercussions. The only other drawback is the cost and difficulty of the design.
Pushrod suspension: This type is usually never used on road cars, and can mostly be found on racecars. Pushrod suspension shares many elements with other types of suspension, like having control arms that are connected to the chassis and to the wheel hub. But where it differs from the rest is the way in which the shock absorber is actuated.
This suspension doesn´t have a shock absorber and spring directly connected to a control arm. For the car to actuate the shock absorber, it must somehow transfer the motion of the wheel going up and down to something that can then actuate the shock absorber. For this they use a torsion bar, which is connected to one of the control arms. As the control arms pivot, so does the torsion bar, but the torsion bar isn´t connected to the chassis, it´s connected to a device called a rocker. The rocker is a triangular device which is connected to the chassis of the car, and pivots on its mounting point with the chassis. As the rocker is pushed by the torsion bar, it spins. The shock absorber is also connected to the rocker via a shaft, so when the torsion bar moves the rocker, it "pushes" on the shock absorber. For that reason, it´s called pushrod suspension. A derivative of this suspension is called "pullrod" suspension. It differs from pushrods because the suspension pulls a special shock absorber which functions in reverse. Aside from that, they are both identical.
The pros and cons of this type of suspension are:
Pros: Due to the fact that most ractracks are very flat, racecars don´t need alot of suspension travel. They must only maximize the contact between the road and the tyres to have as much grip as possible. Therefore, having a very stiff suspension which minimises body roll and maximises grip in this circumstance is very helpful. So, pushrods are inherently stiff due to the fact that this design usually doesn´t incorporate enough space for long springs or long shock absorbers. This suspension also serves an aerodynamics purpose, especially for open wheel racecars like F1 cars. These cars all use pushrod suspension because, if they were to use any other type of suspension, the shock absorber would be causing drag and disturbing the airflow in that region. With pushrods, the shock absorbers are inside the car, and away from the freestream air. In these cars, the control arms are usually shaped like an aerofoil to minimize drag.
Cons:
This type of suspension is not intended to offer the car´s occupants comfort. This suspension is also very complex, and is therefore inherently very expensive. On the road, being usually so stiff, the car equipped with this suspension might become slightly airborn if the car hits a bump at high speed thats to much for the suspension to handle.
That´s it for today´s post. I mainly wanted to focus on the best and most popular types of suspension, and since there are so many types out there, I couldn´t really talk about all of them. The ones I mentioned earlier are the ones which most people will find most relevant. I do hope that this might help some of you choose the right car with the right suspension for your needs. As I always say, I am still a pretend engineer, so if you are a real engineer and you spot a mistake, please let me know.
Ciao for now!
Before we discuss the different types of suspension, let´s ask for a moment: why do cars need suspension anyway? There are multiple reasons:
1. Comfort and handling: car suspension absorbs all of the abnormalities of the surface the car is driving on, minimising the amount the car is disturbed and making sure that the car doesn´t veer excessively off course due to a bump.
2. Performance: the suspension also ensures that the tyre(arguably the most important part of a car) stays in contact with the road for as long as possible, and throughout a wide range of conditions. Therefore, a car that has the correct suspension setup for the application will be faster and safer.
Most popular types of suspension
Double wishbone suspension: This type of independent suspension (one wheel doesn´t affect the other when hitting a bump) was relatively rare in the early 20th century due to it´s cost and complexity, but nowadays is available on many high end comfort oriented cars. It consists of two wishbone shaped arms (one above the other) that connects the chassis to the wheels. These two arms pivot up and down from a centre axis, allowing the wheel vertical movement. This type of suspension also features a shock absorber and spring, which connects the bottom wishbone to the chassis.
The wishbones on this type of suspension are usually of unequal length (usually the top wishbone is shorter) to make sure that the wheel goes up and down as straight as possible, minimising camber change. This type of suspension is very versatile allowing engineers to optimise the suspension for comfort, sportiness, or even both at the same time!
The pros and cons of this type of suspension are:
Pros:
This type of suspension can be used in a wide variety of vehicles, is still relatively simple; and due to it´s design, offers the engineers more parameters to optimise the suspension for the application.
Cons:
These suspensions are more expensive than other types, they usually fill up more space do to their size, and is heavier than other types of suspension.
McPherson suspension: This type of suspension is also independent, and consists of a single control arm (or wishbone) that connects to the bottom of the hub of the wheel. The bottom of the shock absorber is connect to the top of the wheel hub; and from the top to the chassis. It is usually found on the front of many cars, especially if they are front wheel drive.
The pros and cons of this type of suspension are:
Pros:
McPherson suspension is very cheap to make, is very simple and more compact than other types of suspension, allowing for smaller cars that aim to offer good ride and handling characteristics while lacking the space for a double wishbone suspension.
Cons:
This type of suspension is so simple, it doesn´t give engineers much room to improve it´s characteristics.
Due to the design, the wheel follows a curve when going up and down (camber change) and; due to the position of the shock absorbers, it usually raises the centre of gravity of cars fitted with this suspension.
The pros and cons of this type of suspension are:
Pros:
This suspension features most of the double wishbone´s pros, but without most of the drawbacks. This suspension allows engineers to optimise the design for the specific application, and is very light, allowing for this design to be implemented on many cars.
Cons:
When used as a front suspension setup, as the front wheels move as the driver turns the wheel, the suspensions geometry changes slightly; as the steering movement torques the arms, although the engineers design the suspension to allow this to happen without any real repercussions. The only other drawback is the cost and difficulty of the design.
This suspension doesn´t have a shock absorber and spring directly connected to a control arm. For the car to actuate the shock absorber, it must somehow transfer the motion of the wheel going up and down to something that can then actuate the shock absorber. For this they use a torsion bar, which is connected to one of the control arms. As the control arms pivot, so does the torsion bar, but the torsion bar isn´t connected to the chassis, it´s connected to a device called a rocker. The rocker is a triangular device which is connected to the chassis of the car, and pivots on its mounting point with the chassis. As the rocker is pushed by the torsion bar, it spins. The shock absorber is also connected to the rocker via a shaft, so when the torsion bar moves the rocker, it "pushes" on the shock absorber. For that reason, it´s called pushrod suspension. A derivative of this suspension is called "pullrod" suspension. It differs from pushrods because the suspension pulls a special shock absorber which functions in reverse. Aside from that, they are both identical.
The pros and cons of this type of suspension are:
Pros: Due to the fact that most ractracks are very flat, racecars don´t need alot of suspension travel. They must only maximize the contact between the road and the tyres to have as much grip as possible. Therefore, having a very stiff suspension which minimises body roll and maximises grip in this circumstance is very helpful. So, pushrods are inherently stiff due to the fact that this design usually doesn´t incorporate enough space for long springs or long shock absorbers. This suspension also serves an aerodynamics purpose, especially for open wheel racecars like F1 cars. These cars all use pushrod suspension because, if they were to use any other type of suspension, the shock absorber would be causing drag and disturbing the airflow in that region. With pushrods, the shock absorbers are inside the car, and away from the freestream air. In these cars, the control arms are usually shaped like an aerofoil to minimize drag.
Cons:
This type of suspension is not intended to offer the car´s occupants comfort. This suspension is also very complex, and is therefore inherently very expensive. On the road, being usually so stiff, the car equipped with this suspension might become slightly airborn if the car hits a bump at high speed thats to much for the suspension to handle.
Ciao for now!
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