Coil Spring rates

First of all, I am not asking any questions or suggestions. I have been reading on getting a stiffer front spring to get a little more flex out of the rear, but I have been finding a lot of calculations and etc. So today I called the various manufacturer's that answered and this is what I got from them (not I think, or calculated) but what the various brands told me what it was. This is by no means a complete list, but this is what I have. I only got the info on the 4.5" and up, (almost all of them). If this has been done before, ignore it.

Skyjacker
XJ 8.0" 235# lbs
6.0" 230

Rockkrawler
XJ 4.5" 160#
6.0" 170#
8.0" 190#

Rusty's
XJ 4.5" 150#
6.5" 150#
8.0" 180#

R.E.
XJ 4.5" (didn't get it)
XJ 5.5" 200#
ZJ 5.5" 220#

Rough Country
XJ 4.5" (Said they would call me back)

PORC
(Sales guy said he thought all of their (PORC) coils were RC's.
XJ 6.5"

You seem to have some reservation about using a calculated spring rate......why is that? It's exactly what the manufacturers in your list do! Note the nice, round numbers ending with 5 and 0......hmmmmmm.......

Great effort on making the calls, however, and for confirming that previous calcs have been nearly spot on.

BTW, the Skyjacker 8's are the best all around coil I have ever run, and I've run 7 different coils in my Jeep,

brokexj said:

First of all, I am not asking any questions or suggestions. I have been reading on getting a stiffer front spring to get a little more flex out of the rear, but I have been finding a lot of calculations and etc. So today I called the various manufacturer's that answered and this is what I got from them (not I think, or calculated) but what the various brands told me what it was. This is by no means a complete list, but this is what I have. I only got the info on the 4.5" and up, (almost all of them). If this has been done before, ignore it.

Skyjacker
XJ 8.0" 235# lbs
6.0" 230

Rockkrawler
XJ 4.5" 160#
6.0" 170#
8.0" 190#

Rusty's
XJ 4.5" 150#
6.5" 150#
8.0" 180#

R.E.
XJ 4.5" (didn't get it)
XJ 5.5" 200#
ZJ 5.5" 220#

Rough Country
XJ 4.5" (Said they would call me back)

PORC
(Sales guy said he thought all of their (PORC) coils were RC's.
XJ 6.5"

Click to expand...

Nope, after searching, I was getting different rates. Since I don't have the springs to calculate my own....I called so I would know what the manufactuer's say they are, nothing more or less.

It's interesting to note how much different those listed rates are. I can't imagine, for instance, running a 190#, 8" spring in the rocks OR in the desert. The roll center of an XJ, especially one with stock-ish Panhard position would make that feel extremely unstable.

To me, even the RE ZJ was a bit soft, but a stiffer shock probably would have masked it.

I love my skyjacker 6" coils. With a bumper and winch I wanted a stiffer spring rate. They are still plenty soft on the trail.

I recently called RE, emailed Claytons, and called Skyjacker.

RE told me for the 4.5" ZJ coils (5.5" XJ), the rate is 185 lbs.

Clayton's 6.5 are 175 lbs.

And the idiot at Skyjacker didn't know. There number is 318-388-0816 if you think you'll have better luck.

Weird that RE is telling you and I different numbers.

Here are Clayton's two responses:

The spring rate is about 175# we have the springs manufactured here in the US to our specs. I really don't give out who our vendors are. Hope you understand. The price is $159 per set.

Thanks
Clayton

This was also informative to hear:

Our springs are designed to give a nice ride on the road and excellent flex off road. The Skyjacker coils are very stiff. If you have a lot of extra weight in the front your better off just putting a small 3/4" spacer in but I really haven't had an problems with our springs and after market bumpers. Our 8" coils are about 200 lbs. Your going to have a harsh ride with the stiffer springs. There isn't treally going to be much difference in compression from a 230 lb spring to a 175 lbs spring. say you add 100 lbs at 230 your at about 7/16 " of compression at 175 your at 9/16" of compression. So that 1/8" your not even going to see.

Hope that helps.
Clayton

RE ZJ's ARE NOT 185lb/in. A simple measurement and calculation will confirm this.

Springs are springs, they are all a chrome silica alloy that use the same modulus of elasticity (Youngs modulus).

Here is a very good calculator that explains the variables and shows the equation:

http://www.efunda.com/DesignStandards/springs/calc_comp_designer.cfm

1996cc said:

I recently called RE, emailed Claytons, and called Skyjacker.

RE told me for the 4.5" ZJ coils (5.5" XJ), the rate is 185 lbs.

Clayton's 6.5 are 175 lbs.

And the idiot at Skyjacker didn't know. There number is 318-388-0816 if you think you'll have better luck.

Weird that RE is telling you and I different numbers.

Here are Clayton's two responses:

The spring rate is about 175# we have the springs manufactured here in the US to our specs. I really don't give out who our vendors are. Hope you understand. The price is $159 per set.

Thanks
Clayton

This was also informative to hear:

Our springs are designed to give a nice ride on the road and excellent flex off road. The Skyjacker coils are very stiff. If you have a lot of extra weight in the front your better off just putting a small 3/4" spacer in but I really haven't had an problems with our springs and after market bumpers. Our 8" coils are about 200 lbs. Your going to have a harsh ride with the stiffer springs. There isn't treally going to be much difference in compression from a 230 lb spring to a 175 lbs spring. say you add 100 lbs at 230 your at about 7/16 " of compression at 175 your at 9/16" of compression. So that 1/8" your not even going to see.

Hope that helps.
Clayton

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i find it interesting to see how different manufacturers dont even seem to know what rate they offer. I guess the average person doesnt care about the #. all i know is, that if they actually put any time into R&D, they should know the rate and publish it. I wish Deaver would make a coil thats progressive and more tuned to rocks and slower stuff. My plan is to get some SJ 6" and remove one coil to get down to 5" with or w/o a spacer.

How many active turns are the SJ 6" springs?

Odds are the inside sales guys are not up to date on much of the tech specs. Every now and again you get one that's on the ball (kind of like Napa vs. Autozone), but most are only looking at part #'s.

CRASH said:

RE ZJ's ARE NOT 185lb/in. A simple measurement and calculation will confirm this.

Click to expand...

So what are they, then?? Since you didn't dispute the above rate of 200 lbs., can I assume that is what they are??

I don't have RE springs, so I can't do any calculations.

All that matters with springs is the length, the spring rate, and max block load (the max weight it can handle before it is over stressed and sags)

Figure how heavy your rig is, Get a spring rate and length that gets you to the height you want. Get a shock length bump stop system that does not let the coil exceed the Block load.

If it feals too soft, then you need different shock valving, not a stiffer spring.
Hideheight should be adjusted with longer or stiffer springs, and ride feal shoudl be adjusted by shocks. Obviously if you have a super stiff coil, you can not add less shock to make it any ofter, and if you have too soft a coil you can over load it and it will sag over a short time.

http://www.pirate4x4.com/forum/showthread.php?t=215114
http://members.aol.com/Stvns/springcalculationR3b.xls

You could use the coilover spring rate calculator for a single coil.
like a 20in 250# spring would be 10in 500# and 10in 500#, block load's would be hard to get from the vendors,

If you want 50/50 flex front and rear, move your engine between the seats.
If you just go stiffer in the front to make the rear work harder on RTI ramps have fun, I dont have anything close to 50/50 flex, my rear is light and when I point the front up a hill all the weight goes to the rear and it does all the work.. thats just how it is..

Using suck down winches you can control the amount of flex on the fly. front or rear suck downs will help you alot more then different coils IMO.
Id get yourself a cheap Harbor Freight winch to mount to the center of your axles and use it to controll body roll, side hilling, wafterfalls up or down.

Here are some BDS spring rates to add to your list.
3" TJ Coils = 158#
4.5" TJ Coils = 175#

3" XJ Coils = 240#
4.5" XJ Coils = 240#

ZJ and WJ Coils are the same as the XJ coils.

J :repair:

Bump for good tech and to add.....

cal said:

The deaver coils are progressive from about 240 spring rate ramping up to 285; they are bout 260 inch pounds at ride height for most XJ's.

Less body roll, less bottoming out, but not a shitty ride.

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Although the quote is from a tard, the numbers should be accurate.

I have done a bit of suspension tuning on things besides jeeps and these are some things I have assumed to be correct but doesn't sinc with info I see here so I may be incorrect.

a coil spring is a really long torsion bar. Making it shorter or thicker gives it a stiffer spring rate but you will lose spring travel. I suspect that spring rate is squared so when a 200# spring is compressed one inch, the rate is 200# but it takes 400# to compress it the second inch. I don't think a automotive coil spring can be compressed to the point of damage without binding the coils. If you are on the bump stops and have available space between the coils cutting the spring will make the spring stiffer but you will need a spacer to regain the height. Using a spacer without cutting the coil will raise the vehicle the thickness of the spacer and will not change the spring rate.

I would use sag to learn about the spring rate and use damping to work between suspension packing over washboards and amount of travel used on simi-big hits and G-out type compressions. Damping should be used to control the spring and the spring controls the load.

I am really interested in the wire diameters/number of coils of each of these products and if the springs were compressed to bind to measure rate.

What about pac springs?

pac publishes all of their spring rates in their catalogs. They have a pretty wide range.