I have the Cusco Zero2's, when i got it in mail it did not came with the upper mount. Can someone explain the advantage of having the pillow ball upper mount over the fixed one. I know it improves the steering response...but how? that is my question...and is it noticeable on a track??

Thanks for any input!!!

 

A pillowball is just a hard steel spherical bearing. It allows a lot less deflection than stock, transmitting more of the road surface's irregularities to the driver. It is a very noticeable difference.
EDIT: spelling

 

Pillowballs are pretty much pointless on a double wishbone suspension like that of the Z. There is very little deflection on a DW setup. You also cannot change the camber by moving the shock on a DW setup.

On a MacPherson strut suspension, there is significant side loading since there is no upper control arm. Thus you see lots of guys running the pillowball/camber plate setup.

 

Not really, because your mounting the upper part of the strut to the car, as the suspension goes through its travel the strut pivots off the upper mount. A pllowball (hi-misalignment spherical bearing) compensates a bit better than a rubber hard mount so there is less side loading of the strut.