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Can anyone explain spring rates to me..? I 'm looking to invest some $$ in a set of Tokiko Illuminas and Tokiko spring or the MSA set for a street 74 260..I want the Illuminas because I like the idea of being able to adjust the ride quality but I don't have any idea how specific spring rates are going to influence that or not..The MSa spring are apparently stiffer than the Tokikos and unfortunately the Eibach progressive (which I hear are more along the lines of what I need)re no longer available for the z..

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I just bought a set of the Eibach progressives from MSA less than two weeks ago, they are still available for the 240 at least, perhaps not the 260's.

The stock spring rates were around 100-110 lbs/in so if the aftermarket springs are 10-20% stiffer you can figure 120-130lbs/in.

There were slight differences between the 240's, 260's and the 280's spring rates because of the weight of the cars. I'd have to look it up to ge the correct spring rates. But this at least will give you an idea. For the street I would definately stay below 150lbs/in or your ride is going to be terribly stiff. Couple that with stiff strut cartridges (high compression/rebound) and you will have a "kidney buster".

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  • 3 years later...
The stock spring rates were around 100-110 lbs/in...

I'm not writing this to say you're wrong, but I went out and measured the springs on my '72 240Z and used the calculator at http://www.proshocks.com/calcs/coilsprate.htm to callculate the spring rates:

LF: 0.4174" (thickness) x 4.5" (outside diameter) x 10 (active coils) = 62.7#

RF: 0.4167" x 4.5" x 10 = 62.2#

LR: 0.4481" x 4.5" x 10 = 85.2#

RR: 0.4555" x 4.5" x 10 = 91.4#

I had read somewhere that the left front is a little longer than the right front, but that shouldn't affect the rates, just the ride height I guess.

FWIW, I have a set of 2" lowering springs on my old 260Z that's currently up on blocks at mom's. I'll measure them this weekend and let you know.

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I have Arizona Zcar springs, 180# front and 200# rear and Illumina's and the ride is not bad at all with the shocks turned down. Turn them up to 5 and the ride is like a dump truck. The shocks determine the ride quality more than the spring rate (with in reason of course).

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I'm not writing this to say you're wrong, but I went out and measured the springs on my '72 240Z and used the calculator at http://www.proshocks.com/calcs/coilsprate.htm to callculate the spring rates:

LF: 0.4174" (thickness) x 4.5" (outside diameter) x 10 (active coils) = 62.7#

RF: 0.4167" x 4.5" x 10 = 62.2#

LR: 0.4481" x 4.5" x 10 = 85.2#

RR: 0.4555" x 4.5" x 10 = 91.4#

I had read somewhere that the left front is a little longer than the right front, but that shouldn't affect the rates, just the ride height I guess.

FWIW, I have a set of 2" lowering springs on my old 260Z that's currently up on blocks at mom's. I'll measure them this weekend and let you know.

SuperDave:

I think your measurements and calculations might be off just a little.

According to the written spec.'s for the 240Z's....

the number of "active" coils is 8.5 on the 72 240-Z's. (10 is the total number)

the outside diameter is 4.35 in.

and the spring constant given by Nissan is 83 lbs/in for the front springs

Nissan spec.'s show a Free Length of 15.2 inch and an installed height of 7.9 inch for the RF - when loaded with 604lbs. So 15.2-7.9 = 7.3 and 604/7.3 = 82.74.

The LF = 14.7-7.9=6.8 with a load of 562lbs So 562/6.8= 82.65

The Rears = 14.5 - 8.4 = 6.1 with a load of 635 lbs So 645/6.1 = 104.1

If you run the above numbers from the written spec.'s given by Nissan - in the ProShocks calculator you listed - they come out pretty close...

FWIW,

Carl B.

Carl Beck

Clearwater, FL USA

http://ZHome.com

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Can anyone explain spring rates to me..?.......

As I understand it...

A coil spring is designed to work under compression.. the "spring constant" is an expression of how much the spring will compress in length, when loaded with a specified weight (pounds of load per inch of deflection) in the middle 60% of it's length.

Coil Springs hold a more or less constant rate, once they are compressed past their first 20% of free length, and before they reach 80% of their free length. In the first and last 20% of their length, their spring rates can vary greatly from the rate of the given spring constant.

I 'm looking to invest some $$ in a set of Tokiko Illuminas and

Tokiko spring or the MSA set for a street 74 260..I want the

Illuminas because I like the idea of being able to adjust the ride

quality but I don't have any idea how specific spring rates are

going to influence that or not..

Higher spring rates (constants) will of course make the car ride more firmly. As the terms "ride quality" and "more" are pretty subjective... each person has to decide how "firm" a ride quality they can accept.

Personally - given the super light weight of the 240/260Z's - I wouldn't want spring rates much more than 20% higher than stock, if I planned to drive it on the street.

The MSa spring are apparently stiffer than the Tokikos and unfortunately the Eibach progressive (which I hear are more along the lines of what I need are no longer available for the z..

I would suggest that you find out what the spring constants are for any of the after-market springs - before you consider buying them, so you will have an apples to apples comparison.

FWIW,

Carl B.

Carl Beck

Clearwater, FL USA

http://ZHome.com

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  • 3 weeks later...

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