Best Coilover Shock Spring Compressor

[bret]

You might think about using a shorter spring with a bit more spring rate. If you need that much preload...you may have too soft and too long a spring.

[bret]

The thing about a long soft spring...a coilspring only has a certain amount of travel available until the coils stack solid. With a good cold wound American made spring, this usually happens at about 40% of free height...meaning that a 10" free height spring will offer approx. 6" of travel until coilbind. So if you select a spring that requires 2 or 3" of preload, you have sucked up a large portion of your available spring travel before you've even started.
Manufacturers will vary, but most coilovers will have a threaded area of the body that is from 1.5" tall to full length thread. This allows you anywhere from a little to a lot of potential ride height adjustment. The problem comes when you use this threaded adjustment as a bandaid for a spring the is too firm or too soft. The correct rate spring should carry the static vehicle weight with no more than about 1" of preload. If you have to go much over that you should try a firmer spring rate and back off the preload.

If you are looking for some help with selecting the correct spring length and rate, this might be of some help: http://www.ridetech.com/info/spring-rate-calculator/

Hope this helps!

[dhutton]

You might think about using a shorter spring with a bit more spring rate. If you need that much preload...you may have too soft and too long a spring.

I learned this the hard way. What Bret is suggesting is the way to go based on my experience.