nzk

need some info on the benefits of corner balancing and what to set up for the Z. taking it to a local race shop tomorrow to get alignment, ride height and corner balance. i track it maybe 3-4 times/year. figured since i have coilovers now might as well get them sorted.

what should be my goal? 50/50? more weight to the rear? what about side to side? i want a streetable ride height so im not going to slam it. is it even worth it? am i going to notice a difference on the track? how about the street?

acrace

I have only an initial set-up on my car and it's used for autocrossing, not track days, so I'm sure that it will evolve and it may not be the best for you, but I would aim for near zero cross weight difference as a priority. My car is 51.1% front and 48.9% rear, with near zero fuel load.

Make sure that the basics are done when the car is being corner-balanced (i.e.: sways disconnected, fuel load where you want it, driver weight properly simulated).

I think it's worth doing.

jlutherva

What does this process involve? How do you move weight around?
Cheers,
Jim

0C_Williams@RPM

Here...I gleaned some of this from the web, added my own touches & experience and cobbled this together. I'm sure I missed some points but it gives you a good a basis to see how the process is done.

You need four scales (one for each tire--there are scales made specifically for this. Look for a racing shop near you and see if you can rent a set for an hour or two) and some way to adjust your suspension. Ah. That's the tricky bit. There are several ways:

1. Coil-overs. Turn the spring perch and it raises or lowers the suspension. Most coil-overs have pretty high spring rates so a little turn does a lot.


2. Transverse spring with ride height adjusters - as in the stock C5 & C6 - more difficult than coil-overs as the spring rate is soft, compared to coil-overs, and it will take more "turns" on the adjuster to move weight.

Corner weighting is a circular process - i.e.; start with all the basics as close as possible to where you need them to be.

1- ride height
2 -tire pressures
3 -alignment
4- fuel load
5- driver weight
6 - suspension travel uninhibited - sway bars neutral (disconnect 1 end link front and rear)
7- when done, re-check it all and if you need to readjust ride height, alignment, etc....start over, hence the statement of a "circular process"
8 - when really done, connect sway bars neutral

Next, you need four scales and they need to on a level surface or in a proper roll on rig. Some shops are clever enough to have roll plates to allow the suspension to "set" after each adjustment.

Obviously, you need to place the car on the scales and record the weights.

Lets say the initial weight looks like this:

Left Right
Front 798 835
Rear 895 802

Now, the trick here is to figure out what the weights should be. Ideally, every tire would carry the same amount of weight ((798 + 835 + 895 + 802)/4 = 832), but that's not possible without physically moving components so you have to figure out the best that is possible.

Here's how:

First, add up the two front tires' weights to get the weight of the front of the car (798 + 835 = 1,633 lbs in my example). Next, do the same thing for the rear (1,697), the left side (1,693) and the right side (1,637).

The thing to understand here is that whatever weights you come up with for each of these calculations (for your car), those are the numbers. Unless you start moving parts around inside the vehicle (like, for instance, moving the battery to the trunk), the relative numbers won't change, regardless of what adjustments you make to the suspension.

Ah, but there's a loophole:

You can't change the total weight on the front or left or right or rear, but the distribution of weight between the two tires that comprise each of those measurements can be changed. That's what we're here to do.

Next, figure out what percentage each side of the car's weight is of the entire vehicle's weight. In my example, the left side is 1,693 / 3,330 = 50.84%; the right side comes out to 49.15%.

Almost there. Now, if the front of the car weighs 1,633 lbs and the left side is 50.84% of the car's weight, the front left tire's share of the car's weight should be 1,633 x .5084 = 830.2 lbs. Using the same logic, compute the values for the three other tires and you should come up with this:

Left Right
Front 830 803
Rear 863 834

Comparing this to the actual figures you find the weights need adjusted as follows:

Left Right
Front +32 -32
Rear -32 +32

It's coincidental that the same numbers are at both ends of the car in this example (you won't always see this) but the diagonal arrangement of the pluses and minuses is ALWAYS there. That's how it works.

If there's too much weight in one corner there's also too much weight in the opposite corner. In fact, that's the whole basis of corner-balancing.

Think of it like this: If you put a jack under the right rear tire of your car and lifted it high enough, eventually all of the weight of the car would be distributed between the right rear and front left tires as the other two tires would be off the ground. As you started letting the car down and the other two tires started to touch the ground, some of the weight of the car would start to be transferred onto them until, eventually, you were all the way to the ground and the weight was more or less evenly distributed.

At a much more subtle level, you can do pretty much the same thing by adjusting the ride height at one or more corners of the car. For instance, lowering the right rear corner of the car a touch will make it AND the opposite corner (the front left) press on the ground a little less. As they press a little less, the other two tires (back left and front right) will have to pick up the slack because, after all, the car still weighs the same amount and all of that weight has to be supported. So, by lowering the right rear you simultaneously reduce the weight on the right rear and front left while increasing the weight on the opposite two corners.

With a few go-arounds of adjusting and weighing, you can dial in the balance until each tire is carrying its appropriate amount of weight.

Unless you have weird ride-height issues (or a bent frame), or started out grossly out of adjustment, you can usually get the car balanced by adjusting just one of the corners, but sometimes you have to do two.

40YRW8

C Williams is right. I would like to add a little to that. Since you are going to a race shop, you have already made the best first step. The total of the right front/left rear should equal the total of the left front/right rear. The importance of this is if one side or the other is more, that is called "Wedge". If your right front/left rear is more, the car will probably be loose on right turns and tight on left turns. The opposite is true if the left front/right rear is more. When you get really good at feeling the chassis work, you can actually tune the car a little for benefitting a right or left hand track or to optimize a particular corner on a course such as one that leads to a long straight. That could actually reduce your lap times even though it might cost you a little time on the opposite corners. The key word is a "Little". When you are at the race shop, ask them to explain "Roll Couple" to you. That is rarely talked about here but it is everything you are trying to get your suspension to do. Oh, CRAP. All this talk is causing me to really want to race my car. Sure wish I could afford it. Good luck and be safe.
Gary

jlutherva

Thanks for the explanation guys! I sure am glad I read this because it really struck a nerve! I'm moving up to race tires for the next event and will be getting a new alignment with more camber. This is going to lower the car and I presently have about -.1 inches of clearance. This thread saved my new side skirts!

I'm getting poly bushings installed in July at Vengeance Racing in Atlanta so I'll have them do another alignment and a corner balance and adjust the ride height up a little.

Jim

SmokinZ

Last year I went through the coil-overs, alignment and corner balancing.

In this thread I posted my sheets if you want to compare:
http://forums.corvetteforum.com/c6-z...1-results.html

Corvee

Let the pros handle it. Take it to LG Motorsports and let Anthony balance your car.

40YRW8

I agree. Since you are already in Dallas, go see Lou. If you have them set up your car, have them tell you what they are doing and why. It will soon all begin to make sense.
Gary

Painrace

There are plenty of race shops that know what to do. LG is one of the best. I agree with taking it to Lewis and Anthony.

Jim

MitchAlsup

I would like to add to C William's nicly done corner weighting essay::

Start with driver's weight in the drivers seat (lead weights) and 1/2 tank of gas.

Take everything out of the car that will not be in the car on the race track.

Put the tire air pressures are hot (not garage) pressures. So instead of 30 cold PSI, you should be doing this with 36-40 (hot off the track) PSIs. After done, reduce the pressures back to normal garage pressures.

Z Fast

I do all of my own set up (ride heights, corner weight and alignment) before each race weekend for my spec miata and agree with most everything said on this thread....good info!

I have one question regarding ride height for our Z06. What is the stock ride height, rake, and where is it measured from? Please don't say the fenderwells as that is an unreliable measuring point. I was thinking that the tie down points in the chassis would be reliable but feel they are too far inboard for the best accuracy.

Tom

4GS7

This thread makes me happy. This should be your first step after you bolt adjustable ride height suspension to your car. Play with damping, sure, but this is an important step that people overlook a LOT.

jamsvet

I had Dick Guldstrand set mine up. What a cool guy.


He said he set my car up so when I lost 25 pounds it would be perfect.

acrace

I believe the reference measurements in the shop manual are indeed from the tie down points.

0C_Williams@RPM

It would be good if someone should put together a complete article and have it become a sticky..

0C_Williams@RPM

the best place ---we use these to make precise measurements = click on this ===>Longacre Chassis Height Gage

0Adam at RSI

Nick,

My Z sits at 50.3 / 50.7.

PM me for the secret sauce!

-Adam

40YRW8

Jamsvet,
I would give my right arm to spend a few hours talking to Dick about the good old days of IMSA. I thought the C-3's he built were the coolest Vettes ever. I don't know if they are still available but you used to be able to buy the wide body kit he developed. And when I say wide, I mean WIDE!
Gary

Z Fast

So does anyone one know what the OEM stock ride hieght is? ...and if there is any rake form the factory. I would like to use this for a starting point before making chnages.

For ride hieght I use my auto laser level. I first make sure my scales/roll off platforms are set to create a perfectly level platform(a must for proper set up and corner balance). I use my auto laser level for this. Then for ride hieghts I leaving the auto laser level at the center of the car I set it precisely at the level of the tire contact patch. From there is is really simple and repeatably accurate to measure ride hieght.

Tom