Originally Posted by Dujo
That said, my understanding about spring rate is that spring rate is essentially a measure of how much weight is required to compress a spring a certain amount. If a spring is already compressed some, doesn't it make it harder to compress it more?
I freely admit my limited understanding of all things car related though. Feel free to expand on what you're saying.
How do KW/RCE's work. I have no idea.
If the spring is a progressive rate, then yes, putting preload on it would essentially increase the rate since you are compressing it to the point that the rate increases. Most coilover springs are linear, so the rate is the same through the entire travel range. A 400lb linear spring has a 400lb/in rate uncompressed, compressed 1", or compressed 3", it does not matter; the spring will always take another 400lb of force to compress an additional inch.
Preload is just stored energy in the spring. If the stored energy in the spring from preloading added up to the weight of the vehicle or more, the springs would not compress at all when dropped on the ground.
RCE/KW's adjust height by adjusting preload only. They do not have a separate height adjustment like BC/ISC etc. etc.