I'm at the point on my truck where I need to figure out the spring rates for my new 2" coilovers. I am running 16" travel SAW's with dual rate kits on all 4 corners. They are all mounted less than 10 degrees off of being stright up and down.

I have designed my suspension to have 4-6" of compression and 10-12" droop (somewhat adjustable). My control arms are around 45" front and rear.

I have noticed a lot of POR posts re: this, but no clear theory seems to have resulted. So what does everyone think about this? How are people setting up their coils? What about front to rear bias?

Squash

Pick up a copy of Milliken's book, "Race Car Vehicle Dynamics." Everything you need to know is in there.

cmk

P.S. Let Ryan know I won't be making it down to the shop tonight. I'm hittin' the auto show with my pops.

No, it's not in that book. I know how to do the math, that isn't the problem.

Squash
p.s. what do you know, you drive a heep anyways :flipoff2:

It's in the book. You have to read more than just the back cover.

The book isn't going to come right out and say, "set up your big blocked, d60/14, long armed, coilovered S-10 with these exact springs." But it will teach you the physics and dynamics behind what the springs do, what dual rate kits do, what effects the angle of the coilovers have, spring rates, etc. You've got to read in to it further and decipher the info. Trust me, it's in there.

cm "at least my junk runs :D " k

Talk about a can of worms!!!!!!

There is a lot of science to it....and a lot of practical stuff too.

Here is a decent link...

http://www.swayaway.com/Suspension%20Frameset.htm

There a ton of factors that are involved. Knowing the overall travel is required is a good starting point. I think coil-overs work a lot better when they are set up to keep weight on the coil at all times. This involves using a very light spring rate. Especially if you only have about a 3rd of your travel being compression. I would also suggest that you give national spring a call. They can help you out too.

later :jeep:

Buddy, I think you missed the point here. Book knowledge is one thing, hands-on experience is another. I don't need to learn how the springs work or how a dual-rate setup functions. I'm looking for someone's experiences.

Squash
p.s. IIRC your junk almost didn't make it home a few days ago :rolleyes:

Ummmmm....ok

I was trying to give you some help. That page gives you a very clean and simple formula for finding out spring rates for your suspension system. Without doing the basic math your not going to have a starting point. If you want more help you might want to post some more info...

-unspung and spring rates would help a lot
-CG and roll center front and back
-wheelbase
-suspension CAD drawings :)
-and your first born

Just kidding. I hope you post some more info.

later :jeep:

You need to know the approx. sprung weight at each corner to tell you how far they will compress at rest.
You need to figure out if you want it stiff in the corners and whoops (which will give up some ramp pts. ) , or do you want it super soft and pliable, but have it body roll in the curves.
SAW site shows a really soft tender spring that coilbinds, then you have a stiff main spring that takes over.
Doetsch likes to keep the main and tender very close together in springrate so that they don't coilbind.
I have Doetsch coilovers with 450/450 ft and 350/350 rear. The front is very firm but rides like a car, and can take massive abuse without a harsh bottom. The rears work great but they kiss the stops too soon on the whoops. I'm going to swap 1 coil on each end and try it (350/450 ft. 350/450 r. ).
I have a problem with mine in that... the machine does not weigh enough to allow me to pre-load the coils (it raises the ride height too much and only gives about 4" of compression) I'm trying to get ahold of some helper springs which will fill the gap between the length of the coils (28") and the length of the shock at full ext. (31" between the spring perches).
My pos probably weighs around 4300-4400 lbs. with D-60s and my ft springs settle about 3" at rest.

Originally posted by dirtrod
[B
I have a problem with mine in that... the machine does not weigh enough to allow me to pre-load the coils (it raises the ride height too much and only gives about 4" of compression) I'm trying to get ahold of some helper springs which will fill the gap between the length of the coils (28") and the length of the shock at full ext. (31" between the spring perches).
My pos probably weighs around 4300-4400 lbs. with D-60s and my ft springs settle about 3" at rest. [/B]

I'm far from being an expert, but why not try a 350/450 in the front and a 450/450 rear? That way you won't squat too much on ledges and you can still romp her in the whoops?

I'm gonna try to do this without spending any more $ than necessary. :)
Actually the rear hasn't been a problem, except when I'm going fast (35 or faster) thru smooth holes or whoops. I can preload the rears, it sets a little too tall, but I could live with it.

Originally posted by Realsquash
Buddy, I think you missed the point here. Book knowledge is one thing, hands-on experience is another. I don't need to learn how the springs work or how a dual-rate setup functions. I'm looking for someone's experiences.

Squash
p.s. IIRC your junk almost didn't make it home a few days ago :rolleyes:

So you want someone to toss out real world knowledge, but you give hardly any info about your truck, or what you do with it:rolleyes:

If you can do the math DO IT! Get some spring rates that are ideal on paper, more info on your truck, then I bet you will get a lot more real world info. Although you have somewhat of a baseline I think more info is needed to answer your question.

Mieser, don't worry bud, Squash was talking to me. We're buds.

cmk

I was flaming cmk ( cmk= :smokin: ), no love lost so to speak! LOL. I haven't checked the sprung weight of the truck yet, that comes this weekend. The whole truck will weigh around 4500 lbs if I weighed all the components right. I meant to post that before! It's also about 108" wheelbase.

I will be running disconnectable swaybars front and rear so I can deal with the body roll from softer springs. I'm also considering having another set of springs to swap in for the trips to the sand dunes and other such right-foot nonsense.

Seriously, I am not looking for the numbers specifically, more a theory of how/why ppl are using what they are using. But other ppl's numbers are all good because it does help me figure out what others are doing.

Thanks all,
Squash

That Sway-A-Way link is money.