Someone Please help me. Rear Suspension

What is the longest spring I can use on a metric car with stock spring mounts? I really wanted to try the 20" but I just cant see it compressing enough to fit. I run a 250lb
11" spring on the lr and a 200lb on the right. I am completely unloading the left rear. If I run the longer spring what would you suggest the spring rate be. I know if I run the same rates Ill only change ride height. I dont have tons of money to just buy several springs and not be in the ball park. Can someone please give me a relative starting point? If I were to run a longer spring on the left would I have to do the same to the right? Thanks.

how much does your car weigh ? you should be able to get a 16" 125-150 in there if you are 3200+, honestly i have never messed with the longer springs with stock spring mounts, but im making an edumakated guess based off my experience with the 20" 100

Car weighs 3500 pounds. Do i only use the longer spring on the lr? I was thinking that I should only do it on the left rear. I dont think I want the "Jack in the Box effect" on the right rear. Is my thinking correct? Anyone know how much spring rate increase ill get by preloading say a 100lb spring, say 3 inches.

Bradley
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dirt2

A 100lb spring with 300lb on it will compress 3 inches

A 250 lb spring with 300 lb on it will compress 1.2 inches

So if your 250lb spring compresses 3 inches it has 750 lb on it.

A 100 lb spring with 750 lb on it will compress 7.5 inches.

If you have more then 3 inches rebound on LR, yes, a longer, lighter spring will work for you. I always used 13 inch springs and going to a lighter spring worked for me. An 11 inch spring would go into coil bind, i would think.