I'm about to install Bilsteins in my C6 Z51, and thought about maybe
lowering the car a smidgen. To get a reference of the current height
of the car, I measured the height at all four wheels, to find it's 1/4"
higher on the right side vs. the left!! It must have been this way from
the factory as I have no mods! (To compare, my previous car, an M3,
was supposed to be slightly higher on the left so that it's flat when the
driver is in the car).

I measured the distance from the ground through the center of each
wheel to the edge of the fender, and the numbers I got were:
FL 26 9/16"
FR 26 13/16"
RL 28 3/8"
RR 28 5/8"

That's a consistent 1/4" higher on the right side for both front and
back. This was measured in my garage.

I also measured a friend's identically configured C6 Z51, and to my
astonishment, his is nearly 3/4" higher on the front and 1/2" in the
back compared to mine, but his was even on both sides.
His measured 27 1/4" on the front, and 29" on the rear.

So.... has anyone actually measured the height of their car before
lowering and noticed an irregularity like this? The difference between
my and my friend's car is a lot bigger than I had expected, from just
car-to-car variation.

Is there an actual spec for the C6 Z51's factory ride height? I'm left
unsure if my target is to "lower by 1/2", then do I go 1/2" lower from
my left side or my right side, or from my friend's car (which are all
different)??? Maybe I'm already more than 1/2" lower than
the "standard" (whatever that is)? At minimum if I opt not to lower
I would think I should get my left and right adjusted to match, but
again I've no idea which to go with (or should I even raise it to
match my friend's car?)

 

Soon after delivery (a few months ago), I also noticed that the left side was lower than the right ( by 3/8-1/2"). Measurements from ground to edge of fender (I confirmed equal pressure in all 4 tires)
FL - 27 5/16
FR - 27 7/8
RL - 28 1/2
RR - 28 7/8
I'm not sure what the height should be, but I know it should be the same from right to left. I plan to have it adjusted at the dealer, then have the alignment checked.

 

I'm not sure what the ride height specs are. There is a big range of ride heights of cars coming out of the factory. However, you should be ok as long as you have an acceptable ratio of front height to back height which some people refere to as "rake." From ride height measurments people have posted in the past your car seems lower than normal. That does not mean it's bad though.

My car came stock with a 1/8-1/4 difference between the right and left fronts and a 1/8" difference between the rears. I think my left measurements were lower. Since you are putting Bilsteins on I recommend lowering the rear all the way(probably won't go down that much) and lower the front such that the gaps between the tire and the edge of the fender is the same between the fronts and the backs. You will be ok at those settings.

Right now my car is about 26 11/16 front and about 28 1/4 rear. I can't get the rear to go down any lower.

 

I've never measured my vette but I did measure my former F150 after having a lift installed. I freaked because I thought the truck was not level and then realized that because my driveway is not perfectly level, the truck's suspension was slightly tilted making it appear as though the truck was not level. I moved the truck to a different spot and the measurements were different. Could be the case with your car???

 

Trim height is supposed to be 46 mm front and 120 mm rear. This is measured as the difference between the bottom of the lower ball joint and the bottom of the inner lower A arm bushing.

 

Do you know what the equivalant measurment differences would be if one measured at the front and rear jacking points(where you put the pucks at) or measuring from the ground to the edge of the fenders?

 

That'd vary depending on wheels/tires, body panel fit, frame alignment, etc. That's why GM specifies trim height the way they do. The GM numbers put the suspension precisely in the middle of its travel, which is where you want it to be for best ride and handling.