Stupid question. What is the purpose and is it really worth it? I'll be putting PFADT coil overs on soon.

 

ttt

 

The purpose is to make a more balanced car. You can only adjust the cross weights, though. Front/Right vs Rear/Left, etc. You can't change the front to rear bias.

It's not cheap and only worth it on a dedicated track car. I almost had it done and then thought to myself, "Why?" I could think of no good answer as my car is a street car that will see some trackdays. Hardly a race car.

IMO, just get the coilovers installed, drive it around for 50-100 miles or so, then adjust them (or have them adjusted) to your preferred ride height (with you in the car) and then get an alignment.

Mine is 26 inches in front and 26 3/4 in rear at the fender peaks with me in the car and equal side to side. I got my alignment (with me in the car of course) today like this:

Front:
Left and Right:
Camber = -.75
Caster = 7.9
Toe = 0.0

Rear:
Left and Right:
Camber = -.75
Toe = -.01

It drives better than ever! Oh I also have C6Z sways. The front is stiffer, but almost imperceptibly. The rear sway is WAY stiffer.

Good luck!

BTW, make sure you pay attention to your tire pressure when you check ride height. Cold vs hot makes almost 1/4 inch difference on my car!

 

The purpose is to maximize equal weight distribution at the corners of the car. Thus, as it rolls down the road, the car has equal weight balance between the left and right sides of the car. When set at stock specs, this does not apply front and back due to the rake (height of rear vs. height of front), unless you specifically make the front height exactly the same as the rear. Height, used in this context, refers to a measurement of the ground to the frame, measured at equal spots, such as near the jacking slots on the frame.

As far as whether it's worth it or not, while in theory it makes alot of sense, in real life getting the exact same height at the right and left corners, both front and back, is nearly impossible.

FWIW, I've done it, with measurements taken every few days to try and get the corners as even as possible before a good alignment. I've noticed that even ambient air temperature can make a difference. For example, this summer I decided to take a stab at it. I wanted a 3/8" (or was it 3/16"; I can't remember off the top of my head) rake between rear and front, so I set the height on all 4 corners to achieve this. Then, I drove the car, and checked it again. It was off. I made the minor tweaks and drove it again over a few days. Again it was off the next time I checked, so I tweaked some more.

Over the next week, temps got hot here (low 100s), and when I went to check again, the car was actually higher, presumably due to higher pressure in the shocks?

Set it again, and when the temps lowered, the car was slightly lower.

I also attempted to set it to accomodate for my weight alone in the the car, which was tough, but after about 3 weeks I had it dialed in as best as I could. Then, I got an alignment. The change in specs was quite large, but I can't say it was due to my corner-weighting, but I can't believe what a difference a good alignment makes. Not only when driving straight, but in sweepers, twisties and everything else. It's even easier to turn, if you can believe that. I can actually feel the difference at all speeds, even with the power-assisted steering we all have.

I've actually been back to the shop a 2nd time for minor adjustments, and on Tuesday I go back again for a final tweak to caster.

I am very happy with how my car handles now, but I'm not so sure the average driver would even notice corner-weighting, unless it was way off to begin with.

Along with a number of factors, you also have to consider the fact that there are bushings that the car sits on at the suspension springs, and as the bushings wear, or are compressed over time, the heights at the corners will change yet again.

As you can tell, I am a picky driver, and am more sensitive than the average driver, which is why I decided to go through this hassle. But, I spent a few weeks dialing in my C4 after I bought it new in 1993, and in the 11 years I owned it, it was never aligned again, nor was an alignment ever again even needed, over 4 sets of tires I went through in those eleven years.

So, is it worth it? I guess the fact that you are even interested in corner-weighting indicates that it may indeed be worth it to you. Based on my experience, my advice would be to not have a shop do it, because they would probably just set it once, and as you can see from what I said above, it takes several attempts to get it as close to perfect as possible. I would also advise when adjusting that you turn the height screws at full revolutions, because sometimes the bushing turns with the screw, and since it's probably already compressed you'll want it to sit in the same orienation, regardless of height, so that the bushing doesn't have to break in differently again, does that make sense? Be sure you do not go by fender height, either, while measuring, as body parts have way too much tolerance allowance. Make sure settings are based between the ground and the frame itself. A good spot is near the little screw near each jacking slot on the frame.

I kept records each time I set it, too, just so I know what caused the height at each corner to change slightly each time I measured and tweaked it, and what I could do get as accurate of a positioning as possible.

Hope this helps answer your questions. If you have any more I might be able to help with, let me know.

Disclaimer: I am not a professional race car driver, nor am I formally trained in automotive engineering.

 

Only thing I might add is if you are happy with the current height of your car,take EXACT measurements on all 4 corners before you remove anything,on as flat as a surface as you can get(which is repeatable preferrably)

If you set your car back up to the same height,your current alignment should remain in tact(Save yourself $100!!!)

Let us know how it goes Chris

 

Aww man I thought the whole point of coilovers was to try to scrape your front lip!

 

He already is!!

 

Corner weights actually have nothing to do with wheel well heights, as the assembly of the body could be far enough off to affect the ground to wheel well measurements. LR+RF/total weight should equal 50% for proper corner weighting. I have digital wheel scales for setting up oval track race cars. I set my completely stock 03 coupe on them. Without ever touching the adjusting bolts the car was within .06% of being equal. Surely this was not by chance, and all vettes are close from the factory on corner weights. For your coil over installation, put the car on scales, set the tire pressures, put about 1/2 to 3/4 tank of fuel in it, get in and read the numbers. Adjust as needed to acheive
LR+RF/total=50%. This sets the left to right balance in the car. The car should turn the same to the right and to the left at this number.

 

Thanks for all the info guys.