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[Yellowjacket]

Well, yes and no....

First lets talk about roll steer. As the body rolls the springs deflect. In your design the spring is fixed at the front and arches upward. When the spring deflects further upward, on the outside of the turn side of the car, since the front of the spring is fixed, the deflection has the effect of shortening the distance from the mounting point at the front to the spring pad. The exact opposite is happening on the other side of the car, the spring is flattening out and is getting longer on the inside, and as a result of body roll, the axle will skew to point the front axle to steer towards the inside of the corner. This will result in the car turning more as the body rolls. This is bad because it is unstable, the more it rolls, the more it tries to steer into the corner. You actually want the opposite thing to happen, as the body rolls the axle should steer less, which provides stability. What you need to do at the very least is fix the rear end of the spring and put the shackles at the front, that would address the roll steer problem. As it is, if you jerk the wheel hard the car is going to turn that much more and that could be dangerous. At the very least it is going to be miserable to drive since the car will be wandering all over the road even if you held the wheel straight. If you hit a mild bump and it deflects one side, that will cause it to steer more and at high speed it will be really dangerous.

Now let's talk about the axle location and the roll center. The axle is located laterally by the springs (as is commonly done with a leaf spring setup). The roll center is the place in space where the sprung mass (the body) rolls around and is based on the geometry of the suspension. For a leaf spring setup like yours, the roll center height is the intersection of a line between the spring eyes, and the contact patch location (center of the wheel). Your roll center is up off the ground a good bit, because your mounting points of the spring are pretty high up in the air. Not sure where your rear roll center is, but you really want to keep the roll axis level or a bit pointed down in the front. If you do a google search on 5 link rear axle roll center you can calculate where it is and make sure your don't have the rear roll center below the front since that makes for a weird feeling car. With independent suspension you typically want the roll center a couple of inches off the ground. You can't get that low with a beam axle but generally lower is better.

If your roll center is too high the car will jack, and that is dangerous. What happens in that case is that as the car rolls the car lifts as well as rolls. Old VW's had a rear suspension that was prone to jacking and we all know they were unstable if they got to the point where they were jacking. Modern tires are so much better, so the forces that can cause jacking are higher and consequently you need to design with lower roll centers than in the past.

You would really like the front spring to be mounted as low on the chassis as is possible to get the roll center as low as you can.

I would rethink the whole thing and use a proper dropped axle and get the springs as low as you can on the chassis.

As it is designed now you most surely will have a problem with roll steer so that needs to be fixed before you drive it.

[88workcar]

I did speak to two fellas today that explained this too. Thanks, I will make some changes.