SundayDriver

If your shocks are soft enough, and you are careful, you can get away with leaving the shocks at their usual adjustment. But again, you need to be careful.

Disconnecting sways is mandatory. Any preload on the sway bars will affect the corner balance, but it is not real. You need to balance the car and then with it still on the level surface, re-connect the sways, ensuring you add no preload to them (in other words, the bolts or connector pins need to freely drop into place withou needing to twist the sway bar. You adjust the drop links to accomplish this last step.

Preload on a sway bar, like a dead shock, can be a real bitch to try to chase down when you are at the track and trying to fix handling problems. Both will tend to show themselves as a problem in one direction but not so much the other, or the opposite effect like O/S on left handers and U/S on right handers. That is the same effect you get when diagonal balance is off.

Bull

+1 Sunday Drover.

In any event, it is unusual for BobbyC's particular car to be 25mm higher on one side, if it actually is (further measurements needed). This coming week's do over should tell something.

SundayDriver

Thanks. The only time you will see this kind of height difference is if the chassis is not square (assuming it is measured at the correct chassis points, and not the body).

I did someone else's Stohr - this is basically a single seat formula car with a full floor and body. The floor was so far off from level (it can be adjusted with the cable supports but this person had never done it) that it was a real mess. I set ride heights and the corners were way off. So I started adjusting corners to see how bad it was going to be. After a few turns of the height adjuster, it no longer made any difference at all. I went to one corner and it was off the ground. This is an extreme example of what happens when you don't do it right.

mark kibort

I disagree as well, as i have seen first hand how changes on each spring corner can change corner balancing . Basically, as you raise one corner, it is pushing down on the tire to raise that corner, thus it will put more weight on that tire, while removing weight on the other. the problem is that by raising that corner, you raise the ride hight and there are trade offs. In the end, the car doesnt have to be perfect, but the cross weights should be close.

you do want to start at the ride hight you want, and then get on the scale. in my case, my driver front and passenger rear are the heavy corners and the car is nose heavy. So, i raise the passenger front about .25" and that bridges the gap. weigh the car. still, the passenger rear is real light. i raise that corner and also drop the driver side front by 1/8" as i dont want to go much lower.

in the end, the cars cross weights are near identical and the front balance is 10% heavier than the rear.

Im no expert in setting cars up, but ive seen it done on TV. And, i did stay at a Holiday inn once.

mk

fatbillybob

I do not think anyone mentioned it yet but the most critical thing in balance and alignment is to make sure floor it flat where you are setting the wheels. Home garages drain water and will sploe off about 1" per car width. That can mean cars with -2 camber will look like -1 on the low side not to mention the messed up corner weights. That fender difference can be the floor flatness. Turn the car the other direction and weigh it again what do you get?

Larry Herman

The guys who do it right either have a professional alignment rack, or use setup pads (like myself). I have a laser that I use to make sure that all 4 pads are in the exact same plane (level and plumb). It only takes about 20 minutes to set it up, but it gives the correct results regardless of how far off the floor is.

SundayDriver

Actually, I mentioned level a couple of times. I use a setup platform and like Larry I have the levels to make sure it it right.

I will point out that the most important aspect is that the four corners create a plane. It can be off a couple of degrees and have little effect on corner weights. Make sure the scales are level side-to-side and you will get decent readings and good camber readings even if front to rear is off a degree or two - that will only shift less than 5 lbs in the readings.

On a somewhat related note, diagonal weights are critical. On my car, 25 lbs of cross weight makes the car a beast one direction or the other. This plays back to level setup surfaces - if they are off, the weights will be off.

analogmike

I dont wan't to nor have time to argue but I would like to help people understand the concept of corner balancing, which many people get wrong.

>>
There is a very direct relationship between adjusting the suspension to corner balance and ride height of any corner you adjust. What it does not do is change the CG of the car - in other words, you are correct that corner balancing does not move weight inside the car, but it does change which corner carries how much.[/QUOTE]

Of course, that is why we do it. But you can't change the ft/rear or left/right percentages
of the car by adjusting the springs for corner balance. For example on my 911 the rear is ALWAYS 60% and the
left is ALWAYS 51% no matter how badly I corner balance the car or how poorly the ride height is set. You guys think you can make the rear closer to 50% by lowering it - you can't. You can't make the left side lighter by corner balancing it.

Your car is what it is, set the springs to do their fair share of the work and your car will handle at it's best on a course with right and left hand turns.

1) Set the ride heights at each corner where you want them, with the driver's weight in the seat.

2) Measure the weights on the 4 corners.

3) Do the math to calculate the CORRECT weights for the 4 corners.
RF = right% * Front% * total weight
or RF = right% * total front weight

4) You will see that one diagonal is heavy by +X pounds and the other diagonal is off by -X pounds. If not, your floor is not level or your scales are of, try again.

5) lower the 2 corners that are at +X and raise the corners that are at -X enough to get the CORRECT weights at each corner WITHOUT changing your carefully set ride heights.

Step 5 is easier said than done, but afterwards your car will be perfect.

If you see anything wrong with that let me know and I can explain better.

340Elise

This stuff is always interesting. So for us newbies who know nothing about CB, who do we believe? Mr. Analog, I haven't read your article (and I will), but what makes you an SME on CB? Not a smart *** question; I'm serious.

As for the others, how do you know you are right? You all seem to be very sure of yourselves, but someone has to be wrong. If you are wrong, then you are doing a great disservice to us CB idiots.

So let's see it; your papers please!

RonCT

My 997S with Damptronics was recently aligned and corner balanced. Here are the specifications for us to chew on...

Weight with 3/4 tank of gas and 165 lb driver (3256 total)
625 622
1011 998

Cross weight 50.2%
Ride height 100mm front, 132mm rear (-20mm rear, about -15mm front from stock) slope of 0.80
Camber -2.3 front, -1.9 rear
Caster 8 degrees
Toe 0.05 front, 0.20 rear

I think that's everything, though I admit I don't know what it all means. But, I thought it might be helpful to this conversation...

mark kibort

I see what you were saying looking back.

Yes, i agree.

so, lifting both rear end point doesnt increase the front to rear weight?

mk



Of course, that is why we do it. But you can't change the ft/rear or left/right percentages
of the car by adjusting the springs for corner balance. For example on my 911 the rear is ALWAYS 60% and the
left is ALWAYS 51% no matter how badly I corner balance the car or how poorly the ride height is set. You guys think you can make the rear closer to 50% by lowering it - you can't. You can't make the left side lighter by corner balancing it.

Your car is what it is, set the springs to do their fair share of the work and your car will handle at it's best on a course with right and left hand turns.

1) Set the ride heights at each corner where you want them, with the driver's weight in the seat.

2) Measure the weights on the 4 corners.

3) Do the math to calculate the CORRECT weights for the 4 corners.
RF = right% * Front% * total weight
or RF = right% * total front weight

4) You will see that one diagonal is heavy by +X pounds and the other diagonal is off by -X pounds. If not, your floor is not level or your scales are of, try again.

5) lower the 2 corners that are at +X and raise the corners that are at -X enough to get the CORRECT weights at each corner WITHOUT changing your carefully set ride heights.

Step 5 is easier said than done, but afterwards your car will be perfect.

If you see anything wrong with that let me know and I can explain better.[/QUOTE]

Joe Weinstein

That's a very well-balanced car. You are very fortunate to
have your car's weight distribution so centered laterally.

analogmike

Very helpful.

BTW good to have scepticism, anyone can claim to be an expert on the internet and everyone makes mistakes.

Cross weights are all you need to corner balance a formula car or other car which is 50% left and 50% right, or 50% front and 50% rear. But our cars are usually heavy in the rear AND on the left so the diagonal including the LR (the lr/rf diagonal) should be slightly more than the LF/RR diagonal for perfect corner balancing. The calculations below will take care of that. But if the diagonals are set equal, it's probably close enough for the racing we do and you won't need a calculator (lazy man's corner balancing).

I have enough ballast on the right of my 73 911, and am a flyweight driver, so it's 50% on the left which makes my corner balancing simple - just get the 2 fronts the same and the rears by the laws of physics must be equal to each other.

Here are the calculations for the above 997S:

total weight 3256

625 622 front% = 1247/3256 38.3%
1011 998 rear = 61.7%

left | right
1636 | 1620
50.25% | 49.75%

calculations show the perfect weights for your car should be:

LF = ft% .383 x L% .5025 x total 3256 = 627
(or can do ft% .383 x left weight 1636 = 627)
RF = ft% x r% x total = 620
LR = 1009
RR = 999

All four of your corners are within TWO POUNDS of ideal, that's as good as it's ever going to get. Your lf and rr are _slightly_ light, and off by the same amount, with the other two slightly heavy also by the same amount, which shows the scales are VERY accurate. The cross weights are not 50%, which is correct since your car is heavy on the left and rear.

All this is independant of ride height and camber/caster, but with enough care you can get the corner balance correct without upsetting the ride heights. But when I am corner balancing it's never easy, after several adjustments I usually end up with one corner that is too high AND too light!!! Lowering that corner to correct the ride height makes the corner balance even further off. Seems impossible but very common. To adjust for this, you lower the two corners on the other diagonal and raise the opposite corner which tilts the car onto the problem corner while adding weight to it.

Good luck!

RonCT

Thanks for the Kudos - Dan Jacobs does a fine job

fatbillybob

How about this?