coils

[boltonbros]

is a 300 and a 350 two close to feel the dual rate?

[partybarge_pilot]

Depends on where you have your slider stop set at.

[BA_DirtDriver]

isn't the initial rate product over the sum?

[partybarge_pilot]

Initial rate for 300/350 would be 161. When the slider hits the stop it goes to 350.

[pciscott]

Multiply the top spring and the bottom, then divide them by the total of the two added together. This will give you your rate per inch. I myself prefer a truck with softer spring rates, you just need to preload them more. When you figure your rate you need to figure how much leverage is on your arm or beams to figure the rate per inch at the wheel. I ran 50lb per inch on my Protruck at the wheel in the rear. Shock valving and staging of bypass tubes does the rest. Some choose to use spring to keep the car from bottoming out, I prefer to use valving. When you add preload make sure you will not coil bind at full bump.

[Stephen]

You can also add reciprocals and invert the sum.

1/x + 1/y = 1/your combined spring rate

Same answer just different key strokes.

I've heard the same answer on spring rates from some other people that seem to know what they're doing. Springs hold the car up, shocks control it.