Suspension and Conering

During conering,suspension was play an important role as a weight transfer from body role.Which mean during cornering the suspension absorb the body from moving left and right,where we call it as rolling in automotive studies.As vehicle rolling the driver and passengger will feel uncomfortable,(suspension system is not only for safety but also provide comfortable driving) the car actually like bouncing left and right,then right and left.

If there are to many rolling for the car,driver will lose control if taking in or enter corner to fast,then crach will happen.For safety reason there is why manufacturer provide better suspension system in every new model release.Usually nowadays they use MacPherson strut,Double wishbone and multi link suspension/semi-trailing arm type.

The very important job of a suspension system is to smooth out the ride while maintaining excellent control. This may sound like a simple job, but with acceleration comes force, and force translates into raw energy. When a vehicle accelerates down a road, bumps cause forward energy to be converted into vertical energy, which travels through the frame of the vehicle. Without coil and leaf springs(usually MacPherson type) to absorb this, the vertical energy would cause the vehicle to jump up off the road, reducing tire friction and control. The car would then come bounding back down with even greater force, making for a very uncomfortable and dangerous ride.

Below is the example of the suspension system for independent system:

MacPherson strut type:

This system is usually use for most widely in independent suspension system for small and medium sized cars.These type are so popular so in FF(Front engine and front wheel transmission)type of car,used as the rear suspension.


Characteristic for MacPherson:

The construction of the suspension is relatively simple.

MacPherson type,have small number of parts,so when it component is less,then less weight.The effects is unsprung can be reduce.

The space for the suspension is small,the usable space in the engine compartment can be increased.

Since the distance between suspension support point is great,there is a little disturbance of the front wheel allingment due to installation error or part manufacturing error.Therefore, except for toe-in,allingment adjustment ordinarily unnecessary.

Spring Offset:

On the MacPherson strut type suspension, the shock absorber act as part of the suspension linkage, bearing the vertical load.However, because the shock absorbers are subjected to the load from the tires, they bend very slightly.

This cause lateral stress (A and B, as shown in the illustration) to be generated,creating friction between the piston road and the road guide, and between the piston and inner shell, causing abnormal noises and adversely affecting riding comfort.

These problem can be minimize by off-setting the spring from the centerline of the strut or shock absorber so that reactive forces a and b generated in opposition A and
B.

Double wishbone type:

This is usually used for front suspension for small trucks and for front and rear suspension for passenger cars.

Characteristic for double wishbone:

Wheels are mounted to the body via upper and lower arm.

Suspension geometry can be designed as desired according to the length of the upper and lower arm and their mounting angles.

For example if upper and lower arm are parallel and have equal length,the tread and the tire-toe ground camber of the tire will change.As a result,it is not possible to obtain adequate conering performance.In addition, in the tread will cause excessive tire wear.

To solve this a design is normally employed in which the upper arm is made shorter than the lower arm so that the tread and the tire-to-ground camber of the tire fluctuate less.


Semi trailing arm type:

Is used for the rear suspension in a few models.

With this suspension,the amount by which the toe angle and camber change(due to the up-and-down motion of the wheels) can be controlled at the design stage, in order to determined the handling characteristics of the vehicle.