Coil Over Spring Rates

[hardline90]

Here is a question for all you Coil Over guys: How do you determine the best spring rate for your vehicle?

I was sure this topic had been covered before, so I spent some time looking on here, but I couldn't find anything, so maybe there are others out there that this will also help.

I am new to coil over’s and currently doing my first build with them and linked suspension. I have purchased a few different springs, but still don't feel like I am where I should be, so before I spend more hard earned dough, I would like to make an educated decision. I know there are a lot of people on here that are close to expert in this matter, so please chime in and help us poor souls out.

 

[UNSTUCK]

To be exact, you need to know how much unsprung weight is on each corner. That's the weight of your rig minus the tires, wheels, axles, and about half the weight of the links and drive shafts. With this information. It's a simple phone call to your spring guy. They will then set you up with the right springs.

 

[I Lean]

Since you have some springs already, set the rig down with only one spring on each coilover, and that will tell you exactly how much weight each corner is seeing.

Example: You have a 300 lb/in. spring on a coilover. You set the weight down on it, and it compresses the spring 4". That corner's sprung weight is 1200 lb.

 

[LT.]

I Lean has a great idea. I ended up shooting from the hip on my spring rates. On the rear I ran a 200 over 250 and on the front I went with a 250 over 350. The rears are perfect and the fronts could use to be a little lighter. You will also need to decide on how much shock shaft you want exposed with the rig at ride height. I was talked out of four inches exposed and was told that I would want more than that.

LT.

 

[TEAM FRED]

Use the calculator on FOAs site.
www.f-o-a.com

 

[neagtea]

Sway Away can help, they have a calculator and are good to work with.
Any of the manufactures can help ya, (saw, king, fox,etc).
Or do like I do and shoot from the hip.
Or buy a bunch of rates and go out and test for a day
I like I Lean's idea I never thought of that as I always used a scale.

 

[hardline90]

I Lean has a great idea. I ended up shooting from the hip on my spring rates. On the rear I ran a 200 over 250 and on the front I went with a 250 over 350. The rears are perfect and the fronts could use to be a little lighter. You will also need to decide on how much shock shaft you want exposed with the rig at ride height. I was talked out of four inches exposed and was told that I would want more than that.

LT.

I am going for about 5" of up travel.

I like Ilean's idea and I didn't know there was calulators for shocks. Thanks for all the help.

 

[hardline90]

OK, I calculated my weight using the method Ilean suggested and this is what I came up with. I started by using a set of 14" 350lbs springs which compressed at 2", so 350 X 2 = 700lbs per corner. That seemed very light to me, so I ran the test again using 14" 125lbs springs which compressed a total of 5" on one side and 5.5" on the other which came out to 625lbs and 687lbs. That just seems to light!!! So using the spring calculator on FOA web-site I came up with a 195 Primary and 130 secondary. Again that just seems to light. What do you guys think?

 

[1995zj]

Details on the rig? Definitely seems light.....but that's probably because I drive a pig.

 

[I Lean]

Numbers don't lie.

Is this the front or rear corners?

 

[Herzog]

OK, I calculated my weight using the method Ilean suggested and this is what I came up with. I started by using a set of 14" 350lbs springs which compressed at 2", so 350 X 2 = 700lbs per corner. That seemed very light to me, so I ran the test again using 14" 125lbs springs which compressed a total of 5" on one side and 5.5" on the other which came out to 625lbs and 687lbs. That just seems to light!!! So using the spring calculator on FOA web-site I came up with a 195 Primary and 130 secondary. Again that just seems to light. What do you guys think?

Gotta remember, that's your sprung weight. Numbers seem normal to me.

 

[hardline90]

This is the front. The vehicle is a CJ-7 with custom frame, TBI 350, Turbo 350 and Atlas 2. I have talked to a few who say there buggies have been heavier than that. I really thought I would have been in the area of and 250 main and 200 secondary, when looking at other rigs similar to mine. Wouldn't that put my rig under 3000lbs? I know it was going to be lighter than I ever imagined, but I just don't think I can build something that light. I don't know, just don't seem right to me.

 

[cjncustoms]

This is the front. The vehicle is a CJ-7 with custom frame, TBI 350, Turbo 350 and Atlas 2. I have talked to a few who say there buggies have been heavier than that. I really thought I would have been in the area of and 250 main and 200 secondary, when looking at other rigs similar to mine. Wouldn't that put my rig under 3000lbs? I know it was going to be lighter than I ever imagined, but I just don't think I can build something that light. I don't know, just don't seem right to me.

That could mean that your tub/frame cage motor trans and tcase and all acc. weigh in around 3k give or take... But you gotta remember how heavy your axles links shocks wheels tires all weigh... So that being said your probably around 4-4500 lbs total weight...

 

[hardline90]

The numbers could be right, but the spring calculator just seems like it wants really light springs. The Jeep is now usable (Not finished, but usable) so I will be going to Crawlfest and I’m going to try the springs I have which is a 250 main and a 125 secondary which isn’t to far off what the calculator wanted. I will just see how it reacts and make a decision from there. Thanks for all the advice!!! I'm excited to give this thing a try. Pray for good weather and I will let you know how it went.