Explanation in the simplest terms I can imagine...
A spring is a certain length when it is unloaded.
When you have 4 springs supporting the weight of the car, each will compress a certain amount, say 1mm each as an example.
Now, to adjust the ride height, we will use the spring collars.
Lets set the ride height to 5mm (still with droop).
The springs will still be compressed 1 mm, but the collars will have been moved.
Now imagine we remove all the droop, so 5mm is the maximum ride height the car can have.
Cranking down the collar another 1mm will not affect the ride height, but the spring will now be compressed another 1mm, making it "pre-loaded".
Newtonian Physics states that every action must have an equal and opposite reaction.
Say the spring is rated 250g force for every 1mm movement.
This 1mm preload on all 4 springs means the springs are pushing "up" on the car a total of 1000g MORE than they would without the pre-load.
So, if you were to push "down" on the car with your hand, you would need to use an EXTRA 1000g of force before the car even started to move (hence it "feels" stiffer, even though the spring is in fact the same rate as before).
Once you've applied that extra 1000g force, the suspension will compress the same amount for any extra given force as it would if the springs were not pre-loaded.
That is, the spring is still the same rate, you just meed more force to actually start compressing it in the first place.
Only a harder spring will make the suspension rate stiffer.
Obviously, this pre-load has a substantial effect on the cars pitch/roll and bump handling - it needs bigger cornering forces, and bigger bump forces, to start moving the suspension.
Pre-load is not desirable unless you REALLY know what you're doing with the car's handling (and F1 engineers REALLY know what they're doing - they're also working with much bigger forces, particularly aerodynamic ones, than we do in RC)
Does this make sense?
Last edited by sosidge; 01-30-2004 at 09:08 AM.