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Discussion Starter · #1 · (Edited)
I've been watching my suspension for a while, and it keeps bugging me. I have Intrax springs on the car, and the rears are a "progressive" style -- three closely spaced coils and two widely spaced coils. The picture below shows the car jacked up.

The thing I'm concerned about is how it works under load. When the car is on the ground, I can see that the three closely spaced coils are compressed completely, to the point where they are tightly pressed against each other. Therefore all the "springing" action is pefrormed by the remaining two coils, which can't be a good thing, can it? The three compressed coils also add to the discomfort as they rub against each other when you rock the car, producing an annoying squeaking sound.

Should I be worried?
 

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Are these Intrac springs designed specifically for a Saab or are they "close" or just plain generic ?

Seems to me that they have not the ability to carry the weight, and that the ride height is now too low ???
I remember "progressive" springs being advertised years ago -- I think all coil springs are progressive, but they must be closely matched to the car's weight - and even then it is a compromise...
Further, to revitalize a 20 year old car, install new or fairly new springs - what an improvement !!
 

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Discussion Starter · #3 ·
earthworm said:
Are these Intrac springs designed specifically for a Saab or are they "close" or just plain generic ?
They are supposed to be a specific part for '94-98 900. At least the label on the box matches the code on the Intrax website.

The ride height seems to be about the same as with other lowered cars I've seen. The front matches the rear height-wise too.
 

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The two bottom coils are more tightly wound than the top three, giving the bottom of the spring a slightly stiffer spring rate than the top.
 

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Discussion Starter · #5 ·
mike saunders said:
The two bottom coils are more tightly wound than the top three, giving the bottom of the spring a slightly stiffer spring rate than the top.
Yes, but what's the point of having five coils if only two of them are actually employed? ;)
 

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They look and sound fine to me. I have the same springs. Well, not sure they are Intrax but they are the Prog ones.
The more weight they have to bear the stronger they get is how my specialist explained it to me.
Even when the spring compresses, the two close to each other may not be "as springy" but they are still helping the shocks and are keeping the car from lowering any farther. They are still doing thier job.
I made a home depot trip and put over 300lbs in my hatch. My rear end dropped maybe a 1/2 centimeter. And that's being generous. I really couldn't see much difference. It blew me away, I was so impressed.
Mine don't make any noise though?!?!
 

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The whole idea behind progressive springing is to allow the lowering to function within the original design parameters of the car. Since the car is now lower and closer to the bump stops, and since bottoming on the bump stops is not civilized, it is necessary to make the springs stiffer. But making them stiffer in a linear manner makes the ride unduly and unsuitably (for a road car) harsh, and can actually contribute to enough of a lack of compliance in the suspension to lead to lack of control (as where the tire ceases to maintain proper contact with the road during hard maneuvering), as well as wearing out other suspension components much earlier than normal. SO, the springs are softer within the early phases of travel (compression) and become progressively stiffer as they near the bottom of allowed travel. Thus a lowering spring that is advertised as 20% stiffer than stock is referring to the relative stiffness in the lower 1/3 to 1/4 of travel. The spring behaves almost like stock through much of its range and gets harder where it counts the most, before you bottom on the bump stops.

Note: Like most things progressive (such as progressive reforms) one is well advised to inquire into the motivations of the progressive to ascertain true intent.
 

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Discussion Starter · #8 ·
Got an answer from Intrax tech support:

"The springs are fine, technically they are a progressive design, however because they are what we refer to as a "barrel spring" the softer coils are really only there to make the spring long enough to have some preload when the car is raised up. This is normal and is really the only way to design a spring for this application, without making it to short to be safe. As far as any minor noise may be concerned, depending on the climate (salt on the roads etc) some of this can get between the coils an cause the squeaking you describe. Two ways to solve it, you can go to Radio Shack and buy some spiral wrap for wiring, this plastic tube can be wound onto the few coils that touch with out taking the spring out and will last a couple of years. It is a relatively cheap fix. Or you can call H&R and they will sell you the same thing for 3 to 4 times the price as their spring noise isolator wrap.

Hope this answers your question."
 
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