determining desired preload on forks

[drumstyx646]

Just got some 1kg/mm racetech springs delivered, and I'm trying to figure out how long I should cut the spacers.

The instructions seem to saying to cut them to a preload of 20mm, measure sag, and then just cut new ones if it's wrong. Call me crazy, but that sounds ridiculous. Is there any way to predict sag based on weight of the bike+rider, so I can measure twice and cut once?

[buffalobill]

You gotta measure the sag with no weight, then with your full body weight on the bike including all your gear.
So they are right, follow their instructions, measure the sag, then make a final cut.

[drumstyx646]

So basically, start with too much, then cut down? Does 1mm of preload = 1mm less sag? I'm thinking the spring rate could be used to calculate at least a starting point...