Okay - First off, I've had WAY too much time on my hands, and secondly, this is an idea discussion group, so please keep the negativity out. If you have a different viewpoint, express it, but explain why.
I was looking to upgrade some parts on my car in the future. I contacted a few companies, to ask some specific questions. One of them sent me this link:
So I went out and did the calculations, and the stock front sway bar comes up around 180 lbs/in roughly, factoring in the motion ratio, with me not having a lift, and good measuring tools, nor patience enough to get more than a rough estimate.
In my searching, I also was able to determine that the Sway Bar's do most of the "spring" work on our cars. This could be why some coil-over packages suck ass, is that they set them up for the sway bar on the car being tested initially. If that's stock, and you are stock, and you get them, they probably ride exceptional! If that's stock, and you're on a Hotchkis or Eibach bar, you're probably noticing the lack of control and the fact you're eating up struts quickly!
But that has little to do with this discussion other than basics of what the sway rates are comparable to the springs. The springs are close enough to a 1:1 Motion ratio to take their rate directly.
First point of discussion:
- When the car is on a lift, and you remove the sway bar, there is about an inch of clearance under the cross member.
- The suspension has an amount of "droop" available. I don't have a jack handy right now to measure that. If anyone here wants to volunteer to post up their setup, and the amount of clearance to the fender sitting, then with the wheel just clearing the ground, it would be appreciated.
I'm going to use an estimate of 6" just to make the math easy here.
The first inch is absorbed by the clearance. That leaves about 5 inches of pre-load. The motion ratio is about .4, so you have about 2 inches of pre-load on the sway bar. Because of the design of the front sway bar, the bar is actually pulling down on the suspension. This means it is pushing up on the body. When you try to accelerate, the body will want to rise. This is done to improve handling, as under braking and turn-in, the nose won't tend to lean as much, and the inside suspension will easily and compliantly drop, as the sway bar is assisting the spring to make that happen.
The basic point is, we may be able to manipulate the pre-load on the sway bars to help control the body motion on drag launches, allowing for much quicker 60' times.
Where the front swaybar is concerned, this would mean reducing the pre-load, which can be achieved with longer bolts on the outside, and spacers which move the mounting point lower. You now have reduced the pre-load on the body, and in effect softened the front suspension. This means that the springs in the rear will transfer more weight to the front. The interesting part is, that if you could get to ZERO pre-load on the front, you would have 180 lbs of force per inch (approximate) helping hold the nose of the car down! Theoretically, if you were to pre-load the opposite direction (providing there is room) you could effectively hold the nose of the car down.
Main advantage of doing this - Higher percentage of weight on the nose.
Let's assume you have a fairly stock car. It launches at around 2.10 seconds on your local drag strip, without losing traction. That's about .43 g's. If the car/driver weigh in at 3100 (A reasonable estimate for most SRT's) then assuming a CG height of an average compact around 20 inches, you're going to get a weight transfer of about 250 lbs front to rear. That's because at 1G, you'd have 590 lbs of weight transfer. Launch for a 2.0, and that goes to .47 g's. 1.9 = 52 g's. 1.8=.58 g's. 1.7 = .65 g's. Notice that this is increasing exponentially the number of g's to go faster on a launch. This means more and more weight transfer.
Let's say you lose traction at 2.1. You have a 63/37 split, so you have about 1950 lbs on the nose. You lost traction at .43 g's average, or at about 1700 lbs on the nose.
By lowering the pre-load on the sway, you've softened the front springs, and stiffened the rear in relation. This means that the car cannot transfer as much weight to the rear, and you will have improved traction.
Now, let's take a look at the rear sway bar. One popular upgrade is a stiffer rear sway bar. Quite often, this is combined very simply with Lowering springs. More often than not, this is then done using stock hardware items.
Let's have a look at the effects that will happen from that: The CG of the car will drop about 1-1.5 inches normally. That reduces the weight transfer at 1g to 545 lbs or so. Statically, we have almost 50 lbs more nose weight. We end up about 1" lower in the front usually, which means we get about 70 lbs of increase in the front rates, plus the difference in the springs. Teins are a popular option, so we will use theirs, which are 170 front, 165 rear, approximate. Compare that to stock at 170/125, and we see no difference in front spring rate. We take a look at the rear, and we add a rear bar that usually is about 170% stiffer than stock. It's attachment point gives it a fairly high motion ratio compared with the front, and we drop it 1.5 inches in the rear. Call me crazy, but this car has a lower CG, less static weight transfer, and a much stiffer rear in relation to the front. It probably gains quite a bit in the launch capability, as the springs are better able to counteract the weight transfer.
If anyone there has a lift, measuring tools, etc., and wants to provide me with some good information, I can much better calculate much of this information....