Suspension systems can be broadly classified into two subgroups - dependent and independent suspension types. These terms refer to the ability of opposite wheels to move independently of each other.

Rigid axle versus independent axle

In the dependent system also called rigid axle, the wheels of the same axle are linked by a solid bar. In this configuration, when the camber of one wheel changes, the camber of the opposite wheel changes the same amount but in the opposite way.

In the independent axle configuration, the wheels are linked to the car body by an articulated system which enables the wheels to rise and fall on their own without affecting the opposite wheel. This fact provides more stability, and better road holding and ride comfort.

The main advantages and disadvantages of both configurations are:

Rigid axle

Advantages: Lower cost, Higher durability

Disadvantages: Imprecise steering, Poor road holding

Independent axle

Advantages: Better road holding, Ride comfort
Disadvantages: Higher Cost, More complexity

Depending on how the suspension works

Let's clarify the main characteristics of each one of these systems.

Passive suspension

Under this name we can include all the conventional or traditional suspension systems.The main characteristic of these systems is, that once they are installed in the car, the parameters of this suspension (stiffness, height) can not be externally controlled. All the traditional springs and shock absorbers are considered passive suspensions.

Reactive suspensions

All current suspensions are also reactive.When a vehicle's wheel rolls over a bump or dip in the pavement, the change in wheel position causes the suspension to compress or extend in response. Cornering, braking, and accelerating similarly cause the suspension to move and let the body roll, squat, or dive. In this group we can include all the suspension systems which are able to control ride height according to changes in weight and in aerodynamic loading. This system is also able to react to internal loading, such as roll and is able to counteract it. An example of passive reactive suspension system is the Kinetic RSF  suspension system from Tenneco. The system has a passive interconnection, which facilitates load sharing between wheels and de-couples many design and operating parameters and modes, such as cross-axle articulation and single-wheel stiffness from roll control.

Semi-active suspension

The main characteristic of the semi-active suspension is the fact that the suspension system can change continuously the damping coefficient, making the shock absorbers stiffer or softer depending on the road conditions. This control is achieved by pairing an electronic control unit with four shock absorbers that have a continuously variable (and controllable) damping  coefficient.Sometimes, apart of the normal coil springs these shock absorbers can be paired with various self-leveling solutions, as well as systems like Hydropneumatic, Hydrolastic, and Hydragas suspensions.

The key advantages of the semi-active suspension are:

1. An adjustable ride, optimized for comfort or handling performance
2. The possibility to select the firmness of the suspension
3. Suspension will automatically adjust according to road conditions
4. Same sized compared to traditional suspension systems.

Active suspension

The active suspension system has the capability to adjust itself continuously to changing road conditions. The system extends the design parameters by constantly monitoring and adjusting itself thereby changing its character on an ongoing basis. Active  suspension systems have a computer that tells a powerful actuator at each wheel exactly when, which way, how far, and how fast to move. The wheel motions are no longer subject to the random interactions between the road and the various springs, shocks, and anti-roll bars. The computer making these decisions uses a network of sensors to measure, for example, the car's speed, longitudinal and lateral accelerations, and forces and accelerations acting at each wheel. The computer then commands the wheel to move in the ideal way for the existing circumstances.

Depending on how the suspension system is built

Conventional suspension

In this configuration the shock absorber is not a structural part of the suspension system. This means that even if the shock absorber is completely worn out or even missing, it is still possible to drive the car to the garage and repair the problem. In this situation the wheel position (given by the lower and upper arms) as well as the height between the car body and the road (given by the spring) will remain the same. In the conventional suspension system the spring and the shock absorber are always mounted separately as two different items.

The shock absorbers used in these suspension systems are called Conventional shock absorbers. The most common attachment methods used to fit this units are:

• Loop / loop type
• Loop / stem type
• Stem / stem type
• Stem / cross pin type

MacPherson suspension

This is currently, without doubt, the most widely used front suspension system in cars of European origin.The system basically comprises of a strut-type spring and a shock absorber combo, the upper part of the coil is supported on the body of the car, and the lower part on a cup (the lower spring seat) integral with the body of the shock absorber, which also constitutes the pivotal axis of the steering. When you steer, the physically twists the strut and shock absorber housing (and consequently the spring) to turn the wheel, the whole assemble turns on a bearing plate or ball race at the top (the mounting kit), and on the bottom ball joint of the lower arm. This allows a twisting motion to take place.