so we have our wheels and our main suspension sorted but now its time to add our front and back suspension, the reason for the other types of suspension is for the different types of animation like i said before the previous main suspension is for rough roads or possibly sharp turns where as this part of the rig could be used to show acceleration or possibly hydraulics use (think snoop dog and his low riders ;)

so in order to make this type of suspension work for the front and the back this is going to need the use of expressions.

expressions are like scripts of code that make a cause and effect like manner on two individual objects i'll demonstrate this through showing the front suspension

so first of make a controller without a deformer (or with depends on how your doing your control layout) and this is where grouping each body part and naming them comes in handy because you'll be using specific parts of the car to operate in certain ways desired.

once the controller is made you go into the expressions editor (window>animation editor>expression editor)

so here we have the expression editor here you would select the object and its transformation value (also here is where the outliner and you will become very best friends) so right now i want to have my front suspension be affected by the use of my controller this is done through the following expresion

Frnt_Susp_grp.rotateX = -Frnt_Susp_Ctrl.translateY

so this expression is telling maya that when my front suspension controller moves along the Y axis the front of the car will rotate ever so slightly on the X axis 

Note: remember to move you pivot point on the body group so that maya knows where the pivot is to rotate

so the desired effect is that the car goes from this.....

to this...

the same is done to the back using a similar expression

Bck_susp_grp.rotateX = Bck_Susp_Ctrl.translateY