Basic functions of a suspension are:

1. Support vehicle weight:
   The vehicle weight is supported by means of springs. Spring rate prescribes the vehicle posture (vertical position and height from ground) and the stroke of tires.
   
   
2. Locate the stroke and angle of tires:
   Suspension Arms (Links) prescribe the orbital movement of tiers. The wheel alignment changes "regulate the handling stability, for an angle and location in the orbit of tires. The suspension arms " are attached to a suspension member or subframe for improving the accuracy of the orbit of arms. "Various input loads are applied to suspension members in driving, with the addition of an engine " and steering gear box in front suspension and differential in rear suspension.
   A stabilizer bar for assistance of a spring is assembled as well.
   
   
3. Absorb forces from ground:
   To protect the body and passengers from the various forces that　arise when the vehicle is in motion and in contact with the ground. These forces are absorbed by the springs and the rubber bushes between the suspension arms and a member and member insulators. The vibrations of the springs are absorbed by shock　absorbers.

There are two basic classifications:

1. Independent suspension - the right and left hand wheels can move independently of each other.
2. Rigid axle suspension - the right and left hand wheels are connected by an axle shaft.

MacPherson strut

This suspension derives its name from the engineer who developed it, Earl S. MacPherson.
In this suspension the upper point of the strut, that has a shock absorber with spring is installed to the body and the lower point is installed to the axle housing or spindle.
The lower arm is connected between the axle housing and the body.
There are two varieties of lower arm. I type and A type because of its shape. It is also known as Transverse Link.

Merits:
As the upper point of shock absorber is high there is little error in the alignment of wheels.
It is inexpensive, as there are very few components.
More space is available for the engine, because of few components.

Demerits:
Some ride comfort may be lost, as it is hard to move smoothly because of bending input force due to the deviation between the strut and input load axis.

Double wishbone

This suspension has a pair of upper and lower arms. Each arms are installed to the body and axle housing. It is so named because the original arm resembled the V shaped breastbone of a bird (a wishbone).

Merits:
It is possible to increase the handling stability, as the suspension stiffness is high and the degree of freedom to control the wheel alignment change and the vehicle's posture is more. Its connection or assembly to a suspension member aids the suspension stiffness and the isolation of NVH.

Demerits:
The structure is complicated as there are many parts, is costly and has lot of weight. Due to the large space required for its installation, the engine room available is less.

Multi link

It has four or five links per wheel, that are connected between the body and axle housing. In many cases, links are installed to a suspension member, as in the double wishbone, but not to the body directly. Generally suspension members are installed to the body by four points. Since the suspension of Mercedes-Benz 190 was named "Multi link" in 1980, cars with the suspension called "Multi link" has been introduced in the Japanese market.


Merit
It is possible to increase the handling stability more easily than the double wishbone, using the most appropriate layout for multi links.

Demerits:
The structure is complicated as there are many parts, is costly and heavy when compared with the double wishbone suspension.

Torsion beam

Trailing arms are installed between the body and wheels and the right and left trailing arms are connected by a cross beam. This cross beam is called a "torsion beam" because it takes the torsion of the car's suspension during cornering etc. There are many types based on the position of installation. The most popular "torsion beam" is a cross beam that is located at the center of arms and is called as "center beam" or "coupled beam".

Merits:
Lot of space is available as there aren't many parts. It is possible to tune the handling stability by combining the cross beam stiffness and the bushing of trailing arm.

Demerits:
A pendulum like rotary motion of the whole suspension could occur as the assembled section of the trailing arm takes the whole lateral force from tires. It worsens the handling stability.