Question about different coil spring designs...

[iammike]

So, been reading on and trying to learn more about suspension and have a question I haven't seen an answer to.

I've seen two types of coils used for lowering springs on a car. One kind has all the coils evenly spaced out and the other has two different spacing ratios.

The attached image is either wrong about the point of this or in some cases the closer coils are used for a progressive approach while others it's doesn't seem to be there for anything more than maintaining preload on the coil at full droop.

Obviously a setup like that isn't NEEDED to maintain preload as the OEM springs and the Corksport springs I've had on my car were evenly spaced...but the Swift springs are not and the coils that are closer together completely compress together when the car is sitting static making them not much more than spacers making the total length of the coil actually doing work shorter.

So, here's my question. Is there something I haven't learned yet on why it might be that Swift, in this case, wanted a shorter length of coil doing the suspension work? Why do they have a design where these "helper coils" only purpose is apparently to maintain preload when other coils accomplish preload at full droop without helper coils?

Advantages? Disadvantages?

(for the record, I think the text someone put on the attached image is a completely wrong analysis of the coil design differences)

[Code Monkey]

Just google up linear vs progressive springs.

[iammike]

Originally Posted by Code Monkey Just google up linear vs progressive springs.

I know about linear and progressive springs...but I don't think that applies when they are dead coils which are already touching each other unless the car is in full droop.

[specvspeedfreak]

2 step linear is what it's called. Bottom portion collapse and act like a helper spring as you said so the spring doesn't fall off the perch on sudden incline, etc. If they made a traditional linear spring it would need to be shorter with the increased rate. Less coil= higher spring rate.

Progressive springs are similar with 2 step in the sense that when initial load/force is applied the coils collapse and become inactive/dead and are essentially a helper spring. However, progressive springs continue with this "process" (for a lack of a better work), aka increasing spring rate, as more force is applied. 2 step linear doesn't since top portion is linear. It's hard to just look at pics and see the differences of progressive and 2 step but if you count the number of coils, how steep the coils winds, etc you will notice the differences. There is more that goes into the spring rate but hopefully you get my point.

Not quite sure if that answers your question lol

[iammike]

It answers most of what I was wondering. Only question left is why Swift used a two-step linear setup. Others have similar spring rates without using that setup so it left me wondering if there was some advantage to it or if it was simply Swift's preference in this case.

[Code Monkey]

Swifts springs are (1) lowering springs and (2) street springs so that probably explains both why they are shorter and progressive.

Ideally you want linear springs, if they are too short and get unseated at full droop, you pair them with helper springs.

[iammike]

Swift springs are linear springs, not progressive in the way you mean. The smaller coils on Swift springs are fully compressed together at anything but near full droop. Essentially acting as the helper springs you are talking about.

[specvspeedfreak]

From swift:

"But bottom line is linear spring is a Swift Springs preferred setup. We make sure that the static spring rate is at the suggested spring rate, and all the way through its stroke from there.
In other words you will be running on the linear spring rate from static height and through its compression.

The reason why we do not reccomend a progressive setup is becasue the rate shifts depending on the load on the spring. All cars have a variance in corner weight so in other words you would be running a different spring rate on all four corners of the car. We have the secondary rate fully collapse at a very light weight, like a helper spring. So yes you are running on a fully linear spring.

Hope that makes sense. I just explained it real quick, but everything you previously stated pretty much covers what I just said."

[iammike]

Perfect. Thanks SpecV.