# Free time + Stock springs = Calculations



## ReVerm (Jan 13, 2003)

This is what happens when I get bored:

Using the figures for wire diameter, coil outer diameter, and model from the FSM, the stock front springs out of my car, and the Young's modulus, Poisson ratio, and density for 9254 steel (courtesy of eFunda), I calculated out the front spring rates for the B14 series cars.

According to the FSM, there are four types of springs in use on our cars. Their color codes and approximate spring rate (with 5 active coils) are:

White: 102~104 lbs(f)/in
Yellow: 106~108 lbs(f)/in
Pink: 113~115 lbs(f)/in
Light Green: ~118 lbs(f)/in

Each of the B14 trim levels have the following springs:

Sentra Base/XE - Manual Trans: White
Sentra E/XE/GXE - Auto Trans: Yellow
Sentra GLE/GXE - Manual Trans: White
Sentra GLE - Auto Trans: Pink

200sx Base/SE - Manual Trans: White
200sx Base/SE - Auto: Yellow
200sx SE-R - Manual: Pink
200sx SE-R - Auto: Light Green

Although these are approximate figures, I think it's pretty safe to assume that Nissan did put stiffer springs in the Automatic transmission cars, probably to offset the added weight of the auto. These results also confirm that the SE-R springs are stiffer than most other B14 springs, but not by very much. Remember, these are only the rates for the _front_ springs. I'll put up the rears tomorrow when I get them cleaned up.

_Please note that these are approximations, not actual measurements. I have assumed 5 active coils per front spring for each of the models (reference spring was from a 1998 200sx base model) and ANSI 9254 Spring Steel for each of the springs._

UPDATE: Due to the rain this morning and me sleeping in, I couldn't get the data for the rears. Sorry. I'm hoping I'll have time by this weekend and have it all up by then.


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## ReVerm (Jan 13, 2003)

*Dammit!*

I did get the rear springs cleaned up, but when I went to go do the calculations, I kept getting spring rates that seemed really, really high. I think it's because the rear springs on our cars are progressively wound, and I'm probably screwing something up in my calculations. So I'll have to get back to all of you with approximate rates for the rear.

What I did discover while doing this though is that I screwed up the calculations for the fronts. I took another look at the front springs, and realized that they only had about *4.25* active coils, _not_ 5 active coils as I used for the calculations above. I must have miscounted somewhere along the line. In any case, this means that the front springs are stiffer than I initially reported. I am editing the original post now to reflect this change. Sorry guys.

_Edit: Shoot. I just realized that I can't edit that post. So instead I'm going to post my corrections as a reply to this thread._


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## ReVerm (Jan 13, 2003)

*Corrected approximate Spring Rates*

Correcting for the total number of active coils (4.25 active coils), the spring rates are as follows:

White: 121~124 lbs(f)/in
Yellow: 125~127 lbs(f)/in
Pink: ~134 lbs(f)/in
Light Green: ~139 lbs(f)/in

As you can see, the spring rates are much higher now. There is also slightly more of a difference between the light green (SE-R)/pink (SE-R and GLE Automatic) springs and the rest. My conclusions aren't really affected, but my numbers were incorrect. I apolegize.


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## ReVerm (Jan 13, 2003)

*Does anyone have a spring tester?*

I've tried all these different ways of approximating the spring rates of the rear springs on our cars (which, as many of you know, are progressively wound), and I keep getting estimates in the *170lbs(f)/in~230lbs(f)/in* range. These numbers seem inordinately high considering the calculated rates for the fronts are in the neighborhood of 120lbs(f)/in~140lbs(f)/in, but because I don't have access to a working spring tester, I can't actually go and measure the rates on them. 

So does anyone here have access to a spring tester and would be willing to measure a set of rear springs for me? 
(You can keep the springs after you test them.  )


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## sfhellwig (Feb 4, 2003)

Wow! Awesome information. I was always curious and I always love to see somebody get technical to this degree. Something I would love to do myself if I ever had the time/motivaton. Sorry I can't help you out with the spring tester. Keep up the good work.

Just noticed the date on the thread. You still deserve the pat on the back.


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## pete? (Jul 6, 2004)

ill check if they have a spring test out at my hobby shop, i doubt they do though.


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## Skinny G (May 9, 2002)

ReVerm said:


> I keep getting estimates in the *170lbs(f)/in~230lbs(f)/in* range. These numbers seem inordinately high


Are you measuring the spring wire thickness ~including~ the coating? Small errors in measurement can produce large errors in solution.

Typical powdercoating on springs is around (but not always) 0.009"

G


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## ReVerm (Jan 13, 2003)

Skinny G said:


> Are you measuring the spring wire thickness ~including~ the coating? Small errors in measurement can produce large errors in solution.
> 
> Typical powdercoating on springs is around (but not always) 0.009"
> 
> G


The spring thickness figures are from the FSM. I didn't measure that.


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