05-02-2007, 09:08 AM
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Registered User
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Join Date: Mar 2003
Location: New York, New York
Posts: 2,476
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 Quote:
Originally Posted by BigSwede
How do you define preload then? How can you load the suspension with more then the weight of the car?
Changing ride height and rake will naturally change the handling but how do you physically change preload?
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Quote:
Pre-loading does not change roll resistant rates (rate from the springs and anti-roll bars). It changes the degree of jacking, and therefore the 'anti-roll' "stiffness" contribution of that effect.
For those who are unfamiliar with jacking effects, think of it as being the same thing as anti-dive, except lateral, not longitudinal - ie - a self-stiffening of the suspension in reaction to the lateral loads being fed thru the a-arms.
When finding that amount of preload that works for your car, you are actually looking for the amount of force left on the spring ( and weight left on the tire) for the particular lateral g level at which the push becomes noticable. It is at lateral loads above that level that you are changing the effect of jacking by actually reducing it a bit.
When the shock tops out, the ACTUAL roll center shifts to (nearly) the center of the inside tire contact patch - for any further roll, the car now pivots about that point. The only way it can pivot is to lower itself, and it is in that lowering that the jacking is reduced.
Roll rate from the springs and bar are not affected at all, as for every degree of roll, the distance traveled (for that remaining spring and bar link) is doubled, and the rate per degree stays the same.
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By "physically" change, do you mean how do I go about changing preload on a spring?
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