Okay, it is 6:40 AM, and I am really bored. So, I am getting closer to going coil-overs, been thinking about the specifics more recently. I had kinda guessed I would want to run 400/300 springs, but i decided to go to Sway-A-Way's site, and use their calculations to see what was what. Here's what i came up with:

Assuming 750 lbs. unsprung weight per corner in the front, and wanting 12" of shock travel, gonna mount CO's at about 15 deg.

Wheel Rate = 156.25
Angle Correction Factor = .9659258
Primary rate = 163 lbs/inch
Main Rate = 400
Tender Rate = 275

So, it looks like i am a pretty damn good guesser, i was only off on the tender rate by 25lbs.
Most of ya'll know what I drive, but just in case:
76 cruiser, 6cyl, SM465, NP205, Rockwells - curb weight is about 4300 lbs. I guesstimated the front end unsprung weight, will weigh it and recalc before i order springs, BUT -

My question is: Most coil-over setups I have seen are using wayyyy softer springs than this. Most 3000 lb buggies are running like 150/100, and even the heavier rigs are still like 250/200. Why is this???

I would like some input from Frankie, Daniel, etc. Any heavyweight guys with CO's - What rates do you run, and what are your likes/dislikes??

I really don't want to have to add a swaybar later--

Originally posted by elf_cruiser

My question is: Most coil-over setups I have seen are using wayyyy softer springs than this. Most 3000 lb buggies are running like 150/100, and even the heavier rigs are still like 250/200. Why is this???


Well there you go; they weigh 3000 lb and you weigh 4300 lb and you are just guessing at that, also they are working with 16-18" travel shocks and you are working with 12" travel shocks. Do the math with those numbers and see what you come up with.

OK, assume a buggy with 16" travel, and 400 lbs. unsprung weight on each front corner:

Wheel rate = 62.5 lbs./inch
angle correction factor = .9659
primary rate = 64.70 lbs/inch
175/100 = ~63 lbs/inch

That still means you need rates like 175/100, according to the math. But i have seen setups like this using rates of 150/50, and 125/50. So why are they springing their rigs too soft??

Originally posted by elf_cruiser
Okay, it is 6:40 AM, and I am really bored. So, I am getting closer to going coil-overs, been thinking about the specifics more recently. I had kinda guessed I would want to run 400/300 springs, but i decided to go to Sway-A-Way's site, and use their calculations to see what was what. Here's what i came up with:

Assuming 750 lbs. unsprung weight per corner in the front, and wanting 12" of shock travel, gonna mount CO's at about 15 deg.

Wheel Rate = 156.25
Angle Correction Factor = .9659258
Primary rate = 163 lbs/inch
Main Rate = 400
Tender Rate = 275

So, it looks like i am a pretty damn good guesser, i was only off on the tender rate by 25lbs.
Most of ya'll know what I drive, but just in case:
76 cruiser, 6cyl, SM465, NP205, Rockwells - curb weight is about 4300 lbs. I guesstimated the front end unsprung weight, will weigh it and recalc before i order springs, BUT -

My question is: Most coil-over setups I have seen are using wayyyy softer springs than this. Most 3000 lb buggies are running like 150/100, and even the heavier rigs are still like 250/200. Why is this???

I would like some input from Frankie, Daniel, etc. Any heavyweight guys with CO's - What rates do you run, and what are your likes/dislikes??

I really don't want to have to add a swaybar later-- here it is first try 5100 lbs machine 175/200 front 175/200 rear way to soft but it would react to the terain great but botoming out was terrible so next step 200/225 front 200/225 rear this was better it still reacted to the terain great and bottoming out was better but if i was only a slow crawler this woud be dreat but as you know i think more is better like say the dam gas pedal so i needed a spring rate that woud allow my agresive driving habit but still ract to the terain so next step was 200/250 front 200/250 rear this was even better and still reacted to the terain but i just drove it harder and battoming was still there so next step 300/350 front 225/250 rear this was the best of both worlds suspension reaction and less bottoming out but i still need bumpstops and there is no way i can get near a road without a sway bar . on this machine i was using 2'' sway away and the reason for this is at the time there where few lower spring rates avalable but i woud rather have a 2.5'' for greater control and now the softer spring rates are avalable so i just orderd fox 2.5'' 14'' travel dam 4 where fawkin hi and i'm shop! as for sway aways formula ? it realy depends on how much shock you wont showing at the shaft more rate more shaft less rate less shaft p.s and valving is another ordeal ;)

Thanks Frankie, that was extremely helpful!!

It is my guess that Sway-A-Way's formulas are designed to give you the stiffest rate you can use, while still having the desired travel. Obviously you can put soft-ass springs on there, and have great travel, but i want stability too. As you said, it bottomed out with the softer springs. I think theier formula also is intended for 50/50 uptravel vs. downtravel...

I dunno though, I will surely be going to a baja shop around here and talking to a real person before i decide what to do. thanks!

and i have 9'' front shaft showing and 9'' rear shaft showing and you can only screw down the second rate untill it will not bottom the spring before the shock is compressd and one time at band camp:D

buy the way i think if you only run front coil overs with rear leaf spring a sway bar will be less needed but i think still needed and you may wont to run much stiffer springs than any formula because of your rear springs you dont wont the front doing all the work do you just my crazy thinking agine wheres my prozak:D

Yeah, you're right frankie, but i am planning on coil-overs for the rear as well. I am just gonna do the front first 'cause i need that more. Then it will flex mainly up front for a while, which is how it works now anyways. then next year sometime I will be putting a front end in back, and CO's, hydro-steer, blah blah - - -

Then it will be a nice balanced vehicle...

SAW's formulas are just a general guideline, every suspension and driving style is different. IMHO those buggies running 50/150 springs are way too light and those vehicle are useless except for pure rock crawling, and they could improve on that as well with a better tuned suspension. The problem with finding springs for most of these rockcrawlers is that they have much more down travel than up travel, so you have to have a real light spring to keep the coils from unloading at full droop. Then you end up with a way too light spring rate that sucks to drive on the street.

The only way to properly figure out what you need for your setup is to calculate/guesstimate a close starting point. Then see how you like it. Then get new coils accordingly.

This is the boat I am in. I'm running a 200/400 coil setup on a 2" diameter 14" travel SAW up front in a severely chopped up 4-door Explorer with D60s. I'm probably at around 3500lbs right now. The spring rate seems to work for me alright.

When I redo some of the front suspension I will probably drop the main spring rate to 350.

The best thing to do on coils is call a bunch of desert racing fab shops and see if they have any used coils laying around that will work for you. A lot of people screw with their spring rates and trade in coils. It'll be cheaper than buying new ones and these may have only been used once.

Originally posted by CoryL
The only way to properly figure out what you need for your setup is to calculate/guesstimate a close starting point. Then see how you like it. Then get new coils accordingly.

This is the boat I am in. I'm running a 200/400 coil setup on a 2" diameter 14" travel SAW up front in a severely chopped up 4-door Explorer with D60s. I'm probably at around 3500lbs right now. The spring rate seems to work for me alright.

When I redo some of the front suspension I will probably drop the main spring rate to 350.

The best thing to do on coils is call a bunch of desert racing fab shops and see if they have any used coils laying around that will work for you. A lot of people screw with their spring rates and trade in coils. It'll be cheaper than buying new ones and these may have only been used once. how much shaft do you have showing a ride height i'm just curious theres no hidden agenda here:D

Mine weighs about 4200 w/ d-60s I'm using 350 over 450 ft. and rear, 5 or 6" uptravel on 15 "shocks 50/50 ft/r wieght bias., works real good, rides nice and handles well at speed.

I'd highly recommend looking at triple rates and stiffer springs. I went from duals up front to the triples and stiffer springs and really like it. Less push away on hills and the stiffer springs keep things under control better (body roll wise). I'm also running 16" shocks with about 9" of droop available so on a shorter shock I may have been able to get the same results without triples.
My truck's about 6500lb total, front springs are 350/450 with King 16" shocks, tender is about 90lbs they say. Rear is 350/350 with about 8" droop, also a 16" shock and coil tender.
I have some playing to do with it still but it works pretty good so far.
Going stiffer yet probably would not hurt anything, or in my case I'm looking more into losing some weight.

cool replys from real world rigs that is awsome if you have a rig with coils and have some facts i woud love to here more and i'm sure elf will to thanks.;)

I run 400#/300# on 2" x 16" Sway a way's in the front.

The Cruiser weighs 6000 lbs, with a 60 front and 70 rear. Big block and 12,000 winch.

When I originally purchased the shocks, the "recommendation" I got was 400 over 200, so that's what I got. The 200's did nothing. I bottomed the suspension going over every little bump. I dialed them completely out until I could exchange them for the 300#.

I may still increase them to 450#/350# as I can STILL bottom the suspension in higher speed wheeling, but they are pretty close.

Tim.

thanx wolf, good info -

I see you're in Snobsdale, uh..I mean Scottsdale:D There's a Sway-a-away dealer in Phoenix called Race shock something or another, I forget the exact name and the name of the guy I talked to, but he was very helpful in discussing this very topic. The desert race shop is a good reccomendation for possibly snagging some used springs. Oh, and I "heard" if you purchase coilovers from avalanche, they will give you 2 chances at nailing down the correct springs, without charging you for a 2nd set of springs to cover the 1st(mistake) set.

I found this website tonight and I thought that you guys could use it. The first is spring rate for daul springs and the second one is for the spring rate at different mounting angles.

http://www.stockcarproducts.com/pstech7.htm

http://www.stockcarproducts.com/pstech8.htm

Remember that you can use the jam nuts to switch from dual rate (soft) to single rate (firm) at any point in the travel stroke. So if you are bottoming out at speed then get on the lower coil (single rate) faster. For slow speed rock crawling I like a firmer lower coil then what the calc book tells you and a softer top coil. Run the jam nut to the coil slider so you are basicly single rate under compression and dual rate only on extension. This gives you better handling and doesn't beat up the top coil. The only trick is you can go too stiff on the lower or you'll give up compression travel.

see ya,

tony k

Buy the coils from someone with a coil exchange program. PM if you need more details.

Originally posted by TONY K

Buy the coils from someone with a coil exchange program. PM if you need more details.


Sounds great...But post the details here please.

--D

That would be pimping and I don't think that's a good idea on a forum.

Send me a PM and then you can tell everyone about it.

see ya,

tony k

I have been on the recieving end these questions when I worked at SAW, I probably did 2-3 of these calculations for people a day, the calculations on the SAW website work pretty well, and I'm not saying this just because I wrote them but I have done it a few hundred times and have found that it works (in most cases). The number one problem that I find (and the first question I ask) is how much does it weigh? (or more specifically, what is the sprung weight) The answer is usually "i dont know, it has 39" boggers, dana 60's, a big block and a 12K lb winch" I would usually respond, "well I cant help you without knowing the sprung weight, I'm not going to guess, but if you want to guess I can run the numbers. The customer would usually guess and most of the time way under estimate the weight, resulting in way too soft springs. I have gone round and round with customers, guessing and swaping springs, fighting with them to weigh the car and take accurate measurements, finally they weigh it, take good measurements and then we nail it.

Any way, my point is that you really need to get accurate measurements in sprung weight and in ride height, wheel travel, etc. Like the saying goes "garbage in, garbage out"

Also, usually you can't go wrong and sometimes end up with stiffer springs, we have fixed quite a few race cars from being bad-handling and dangerous to stable and fast.

Yeah good point GOAT1. As I mentioned I will weigh it beforehand, and redo the calculations.

elf,

Cool deal on the coilovers, they're awesome. My buggy weighs 4940lbs with me in it, full tank of fuel and ready to rock.
Front Weight: 2820lbs
Rear Weight: 2120lbs

Front rockwell: 700lbs ea
42x15" Swampers: 100lbs ea
15x10 MRT's: 30lbs ea
1/2 suspension components and misc unsprung weight...

I am saying about 1100lbs at each end is unsprung weight.

Front Sprung Weight: 1720lbs
Rear Sprung Weight: 1020lbs

Here is my current spring configuration:
Front springs are 200/250lbs
Rear springs are 100/150lbs

I used to have 150/200lbs in the rear but it was too jarring, it needed to be softer, I know that 150/200 is already super soft but I guess as they say every rig is different. I can tell you that when I put the softer springs on, it improved the entire suspension 100%. I had my jeep for a while at the beach and was able to run 30-45mph on the sand and the suspension would just soak everything up, never got air but there definately some big bumps. It was awesome, It was cool being able to pull rooster tails at 20-30mph if you just gave it some throttle :P

One thing I'd like to add is that I think using swaybars is a great idea. Generally on the Jeeps the rear is much lighter than the front and all you need is a rear swaybar to help things out. Swaybars are meant to control body roll and help even out the suspensions so that both work in harmony, instead of the rear maxing out and then the front start working. I think the swaybars help eliminate alot of problems people have with coilovers(body roll, flopping side to side)

I think it is somewhat foolish to use super stiff springs to combat body roll, seems to me your just killing your ride. Drop $2000 on a BAD ASS set of shocks and then not use them to their potential? Kinda like fourwheeling without lockers? :P

Another note. I had to thread the ride height/preload adjuster down quite a bit on my rear shocks to get the ride height I wanted out of the 100/150 combination. While at first I was leary and thought it might tell me I was using way to soft a spring setup, but now my coils can't fall out on droop, the free length of the coils is longer than the distance from the adjuster to the bottom spring cup. I honestly don't see how these guys with stiff springs do it. In order to get ride height where they want with those stiff springs they must be using very short ones, which will drop out on droop?

I guess I'm an oddball since I use such soft rates compared to most of the other guys here but I can tell you it works awesome!

CJ

GOAT,

Can you chime in and help with explaining how the spring natural frequency applies to us? I think I get it and I think around 1 would be good for a rockcrawler? Seems as your speed increases you'd want the frequency to increase which increases your spring rate?

Thanks,
CJ

CJ Lagos, good point about the suspension frequency, but I dont know if it has much use in this case, ( after all, you would really need to get good weights of your car to use it, and that's asking a lot)
But anyway, a good number to hit for a passenger car suspension frequency is around 1 hz, and your right, race cars are usually higher. Typically, you want the rear frequency to be about 10-20% higher than the front, depending on the wheel base, so you get a level ride over bumps. The problem with using suspension frequency in rock crawling is the amount of travel we are using, if you calculate the springs based on frequency, you usually end up with springs that are too stiff to put any preload in the springs, and your coils unload at full droop, like you described earlier.