A lot of people fail to realize what their front and rear springs really are. Most are not mounted 90 degrees. Anything greater than 15 degrees and your springs are no longer what they are outside the car. Read this and study it. It may make a difference. It's one of the first things I look at when asked to look at a car:
Motion Ratio = Dimension A / Dimension B* sin(Spring Angle)
The motion ratio is the mechanical advantage (lever ratio) that the wheel has over the spring in compressing it.
The motion ratio is often squared when calculating the wheel rate, which is the spring's effective stiffness felt at the tire; the formula is Wheel Rate = Spring Rate × (Motion Ratio)², because the spring's mechanical disadvantage (lever effect) multiplies with the ratio of distances from the pivot, reducing the force at the wheel. It relates how much the spring moves versus the wheel, and squaring it accounts for the leverage effect in the suspension linkage.
- Motion Ratio (MR) = Wheel Travel / Spring Travel (or Shock Travel).
- Wheel Rate (WR) = Spring Rate (SR) × (MR)².