Rear Spring Rate?

[bigblue466]

I'm looking for sugestions. How do you know if the rear 4-link springs are too light? Set-up with 170 look good, jack front up untill fronts are off the ground and springs are just about coil bound. It's good too have stored energy but I was just thinking I need to go up some. It will pack the wheels out about 30ft

[Yellowchevelle]

Do you have the weights of the car?

[bigblue466]

No I don't as it is now. When it was a ladder bar set-up it was 3400 with 1938/1462

[Yellowchevelle]

any idea what the unsprung weight on the rear? (rear end, tires and wheel weight)

[bigblue466]

That's a good question. 17-33 GY, 9" 36" OAL, Drums, Shocks I would say a good 300lb just a guess.

[Yellowchevelle]

how much travel does the shock have?

[bigblue466]

5.5"

[Yellowchevelle]

Are they in front or behind the rear end and how far? And how long are the ladder bars

[bigblue466]

Behind and is a four link 20" C/L of rod ends

[want-a-be]

IMO...I think the 170s are a bit high. Might consider something like 135-145ish spring. What is the free standing height of the spring and what does it measure while installed?

Jacking the front of the car up while it not moving really isn't a good representation of whats going on when you leave the line. You have to remember that while you are leaving the line your rear suspension should be trying to seperate. The spring helps that seperation happen.

Don

[bigblue466]

Yea, according to where my IC is. I can make it separate but it is not set up that way.

[want-a-be]

How far out is the instant center and how high is it? How long is your wheel base?

Don

[BillyShope]

I wouldn't be concerned about the results of your test, for it doesn't represent that which occurs on launch. If your 4link is set up for 100% antisquat, for instance, the springs won't compress a bit on launch, regardless of their rate.

Use some 4link software (there's a free spreadsheet at my site) to determine the percent antisquat. I'd recomment 100% or slightly more.
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