Quote:
Originally Posted by glhs386
I've tracked this car on stock springs, 4.5kish front springs and 6k front springs. The higher the front spring rate, the more stable and level the car was under braking, no comparison. With factory suspension and 245 RE71Rs I was practically sawing at the wheel to keep it in a straight line.
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I don't doubt that things improve with higher front spring rate, my point was that the implied mechanism of front spring rate reducing rear toe-out doesn't make sense. It's possible you never meant to imply that, but if you did and there's an error in my logic, please point out at which step I go wrong.
Quote:
Originally Posted by glhs386
Continuing your logic, competition cars running ultra high spring rates (3-5 hz) and slicks would stick their butts three feet in the air under braking. I can't say I've ever seen that, personally.
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I never said it would be a strong effect, only the direction of what happens doesn't fit what you seemed to be implying. A vanishingly small increase in rear height is still not a decrease, and certainly not three feet in the air.
What I suspect you're seeing is a front bump steer effect, not rear. Mcpherson struts are not linear in their camber curve, going flat and even reversing when far enough away from level position, and bump steer is closely related. With stiffer front springs, you're reducing how much of that curve is exercised, keeping it from going to where front bump steer starts doing weird things.