Best $0.00 I've ever spent

Your absolutely right it doesn't change the spring rate. What it does is stiffens the shock and takes more weight to compress it from the start to the same height. For example lets say no preload set. You're 100 lbs and the bike has a sag of 35mm with you on it. It takes 100lbs for the first inch and another 100lbs to compress it another inch. Rate stays the same same 100lbs per inch.

Add a good amount of preload. Now when you get on it it only sags 15mm. Why? Because it takes more weight to compress a partial compressed spring under load over standard install height. Or lets say for example only that the spring has a 100lb rate per inch set at 160mm install height. So it takes 100lbs to compress the first inch. Now add preload making the install height 150mm. Now it takes 150lbs to compress the spring an inch. That make sense? (All figures are just that not accurate just for example)

Go try it on any bike with a preload adjuster on it.

 

If you really want to get a good understanding of your bikes suspension and how geometry plays into the handling of your bike, pick up a copy of Racetech's 'Suspension Bible'. Great info in it and lots of how-to topics, like changing out the valves and shim stacks on forks or rebuilding a shock, if your so inclined and capable.

Another good place to get this info as well as getting some great riding tips is the latest edition of 'Total Control' by Lee Parks. There's a section on how to trouble shoot and tune your suspension. Great read as well.

 

What do dudes do that are 5'3" and come in at 300lb? Monoshock bikes for Sumo Wrestlers?

Buying a Harley is not an acceptable response.

 

http://i913.photobucket.com/albums/ac334/Myolbug/Svc manual forks.jpg?t=1428450658
If this pic is correct I am way off. Mine is completely wrong. Mine is set to the line that is 4 or 5 mm below the top, where they are measuring 41mm I am at about 5mm.
Am I looking at this the right way?

EDIT: There are no bars in the pic..... Doh!

 

A little something to add to the thread, here's a "how-to" on setting suspension sag from Motorcyclist magazine.

http://tinyurl.com/oo59c2t