180 lbs Progressive Springs... Heads Up or Down, Sorry, Stupid Question Time Again Options

[dbledsoe]

I'm installing Bilstein shocks (rear) on my 914 Buick V6 conversion. I bought 180 lbs progressive springs from PP (which were actually shipped from GPR). My question is, does it make a difference how the progressively wound coils of the spring are positioned i.e., close spaced coils should be at the top, or should they be at the bottom?

I apologize for what is probably a very basic question, but doing a search turned up nothing (that I could find to address the question) and I don't have any experience with progressively wound springs.

More photos tomorrow on my slowly advancing Buick V6 into P914 project (this is/was my first 914 [I have two of them now] and my first engine conversion... other than putting a Volvo B1800 engine in a Sunbeam Alpine 28 years ago... and yes I still have it but that was a lot simpler... or maybe I was less hesitant).


Thanks for your help!

Don

[TravisNeff]

Close coils to the top, I don't know why though

[SirAndy]

QUOTE (dbledsoe @ Jun 22 2005, 06:39 PM)

close spaced coils should be at the top, or should they be at the bottom?

big difference indeed ...

i just went through this on my car:

- for street use, close spaced coils at the bottom. this will make them *feel* like they start at about 140lbs and they'll get progressively harder when compressed.

- for AX/Race use, close spaced coils at the top. this will make them *feel* like they start close to 180lbs and they won't get softer when compressed.

(IMG:http://www.914world.com/bbs2/html/emoticons/cool.gif) Andy

PS: running progressive springs "upside-down" to get more stiffness out of your spring is a old trick from my dirt-bike racing days ...

[jasons]

Please explain this to me. I can't see how the orientation of the spring effects whether it is progressive or not. Seems to me, if a spring is wound progressively, the softest windings will always compress first. (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)

[SirAndy]

QUOTE (jasons @ Jun 22 2005, 07:16 PM)

Please explain this to me. I can't see how the orientation of the spring effects whether it is progressive or not. Seems to me, if a spring is wound progressively, the softest windings will always compress first. (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)

kinda hard to explain, i'll try ...

on either a car or motorcycle, you have a fairly large mass on top that doesn't move along the axis of the spring (the body of the car) and a pretty small mass on the bottom that does move along the axis of the spring (your wheel).
when you drive over a bump, your car stays flat and your wheel moves up/down.

it's that imbalance of mass that makes the difference. if your wheel and the rest of the car were about the same mass, it wouldn't matter which way you run the springs ...

(IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif) Andy

[Thorshammer]

I hate to differ, and I am unsure of how you came to this conclusion. But the real answer is, You always run the close wound side of the spring to the sprung mass. or to the car side. because the spring has more weight in the tighter wound section it will add to unsprung weight if it is run with the tightly wound coils towards the trailing arm. There is no compressive difference with the spring either way. Andy may have encountered some very odd natural frequecy which made his react differently with the spring mounted different, but in my experience with suspension, there is no difference. The spring will still reach a steady rate once the softer coils are compressed, this does not change with mounting.

As you compress the spring the closely wound spring sections will compress more quickly, but at a point, they will slow in their compression (or cease if they are coil bound) and the load will be carried by the coils that are spaced further apart. No load changes will occur if the spring is turned around. If Andy did get a significant change, I would look at upper and lower spring seats being different and the spring not resting properly on the spring seats, or a very odd frequency induced issue, but I can not speculate on how that may happen . Maybe I am missing something , but I don't think so.

Erik Madsen

[SirAndy]

QUOTE (Thorshammer @ Jun 22 2005, 08:01 PM)

but in my experience with suspension

i beg to differ ...

thousands of miles on my dirt bikes and now 2 events with my car have shown the same results ....

AX at marina, springs with close spaced coils at the bottom, front of the car was too stiff, sway bar on full soft so i had no bar adjust left, car wouldn't turn in. lots of understeer.
i had to unhook the front bar to get it to turn and then the rear was lose.

AX at alameda, *only* change i made was to turn the springs upside/down. front sway bar hooked up again on full soft, just as at the previous AX.
now i have oversteer from the get-go, car turns in great, rear is mucho lose.
now i can dial in more front bar to get the rear planted better.

in effect, turning the springs upside/down made the rear STIFFER.

which is *exactly* the effect i have seen for many, many years on mine and other dirt bikes using progressive springs ...

(IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif) Andy

[Thorshammer]

Andy,

I have not attempted to say what you have "felt" in your car is not correct, Only to indicate that a progressively wound spring does not know the difference between the unsprung and sprung mass as you have indicated. As the propreitor of a suspension company for nearly 15 years, as well as an Ohlins technical representative to World Superbike and previous Motorcycle road racing Amateur National champion, I still must differ with your conclusions. The only possible way for your car to become stiffer is to have compressed the spring more when it was installed in one direction than the other. I am unaware of this spring design and do not know if it is a closed end spring, closed end with ground ends, plain ends or plain ends ground. if the two ends are different, the changing of the spring orientation can and will be affected, due to the spring seat matching or not matching it's intended location. This is crucial to your argument I believe.

As I stated earlier, the spring orientation will have no effect on overall spring stiffness. This is clearly covered by "Dr. Albert E. Roller.,"Design And Calculation of Progressive Competition Springs," Industrial Mechanics,Vol. 10 Part 1, The Industrial Mathematics Society, Detroit, MI, 1960."( Milliken and Milliken) Ref.133

The mounting of the spring does not and can not change its rate, period. It is physically impossible. However, the natural frequency of the unsprung mass can and will be changed due to the change in spring mass. You are correct about the mass being affected, but not the spring stiffness. It is a simple device, even thought one end is the only moving end, the spring will collapse on whichever end has the least spring rate. this is a physical certainty.

Erik Madsen

[SirAndy]

QUOTE (Thorshammer @ Jun 22 2005, 08:55 PM)

The mounting of the spring does not and can not change its rate, period. It is physically impossible.

i never said the spring changed it's rate ... (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)

i'm saying that the masses on each end influence the way a spring compresses and expands.

as i said before, i have seen this effect work many, many times during my dirt bike racing years. not only on my bike but on others as well.
in fact, i was introduced to this method of changing the stiffness of your bike by a competitor ...

altough i have made mistakes in the past (and certainly will in the future) i refuse your notion that all that simply was a fuckup on my end when mounting the springs ...

the result i got for my car (and on my bikes) is very much "feelable".
to the point that my car went from major understeer to oversteer, simply by flipping the springs.
and yes, they're seated correctly and held in place with zip-ties. just like they were before ...
(IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif) Andy

[SirAndy]

if you put a progressive spring in a spring compressor/springrate gauge you'll get the same reading either way.
but that's because one end (your concrete floor) doesn't move and you're only applying force to the top end.

on a car, you have both ends working on the spring in very different ways ...
(IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif) Andy

[Thorshammer]

I don't seem to be able to make you understand. And you seem to be upset at the challenge of your theories. Please call H&R or Eibach and ask them. I am done attempting to educate you any further. My theory is firmly entrenched in fact. If you need any more information I suggest the previously referenced material. Of which I have on the shelf. You may find it at the local technical library.

Erik Madsen

[Thorshammer]

Actually you did say the spring rate changed by turning the spring upside down.

"- for street use, close spaced coils at the bottom. this will make them start at about 140lbs and they'll get progressively harder when compressed.

- for AX/Race use, close spaced coils at the top. this will make them start close to 180lbs and they won't get softer when compressed"

This is your quote from an earlier post. The orientation of the spring WILL NOT affect its rate. Also the orientation will not affect the amount of exponential change in spring rate. Ride height, will not change, amount of travel for a given load, will not change. compression of the spring for a given load, will not change. Point at which the spring coil binds for the softer side, will not change.

I understand you feel strongly about this, so I don't expect you to believe me, so tomorrow call some one and ask. And be prepared to quote them, and ask them if you can quote them. I await your reply after you consult with your people and they talk to my people, just a joke, Lighten up Francis.

Erik Madsen

[SirAndy]

QUOTE (Thorshammer @ Jun 22 2005, 09:30 PM)

I don't seem to be able to make you understand. And you seem to be upset at the challenge of your theories.

no, i'm upset that my experience is brushed off as "must have been mounted wrong" while your experience is "i'm right!".

i told you what i have experienced over many years and you tell me i'm on crack.
that wouldn't upset you?

i guess i must be dreaming then ...
which is fine with me. i'm sticking to my story as it works for me ...

back to Don's initial question, you should run 'em whatever way you want.
(IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif) Andy

[eeyore]

(IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif)

We were plummeting toward puppy picture posting...

[SirAndy]

QUOTE (Thorshammer @ Jun 22 2005, 09:41 PM)

This is your quote from an earlier post. The orientation of the spring WILL NOT affect its rate.

yes, your are correct, that was my previous post and you're right, the spring rate does NOT change.

what i meant, and failed to word correctly is:

when flipped, it "feels" more like running straight 180lbs springs, rather than the *feel* of progressive springs that start out on 140lbs and get up to 180lbs as they compress ...

MY BAD for not wording this correctly, i apologize ...
(IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif) Andy

[Thorshammer]

Actually,

The "brush off" as you call it was an attempt at giving you a gracefull exit at the bullshit you are trying to post here. The best thing you have said is "I'm right", and I was trying to give it to you easy, but you don't seem to want to listen.

So here goes, Your theory is BULLSHIT, it has absolutely no ability to prove itself and through your own admision was given to you by a old racer friend that told you it would stiffen the bike up. You have zero engineering grounds to stand on and once you check it out, you will see that you are 100 % incorrect. Now, I hope you can get this through you thick head. You are wrong. And don't start pissing and moaning about me being a dick or whatever. Because I tried to show you the right way. And when you get up enough courage to find out the physics involved in springs by either reading or asking. Keep it to yourself. Cause most everyone else who has read this already knows.

Honestly, people like you are the main reason I don't post more technical information here and elsewhere.

Erik Madsen

[SirAndy]

QUOTE (Thorshammer @ Jun 22 2005, 09:55 PM)

people like you are the main reason I don't post more technical information here and elsewhere.

that's a bummer. honestly.

yes, someone showed me how to do this on a dirt bike about 25 years ago.
sorry i didn't engineer it myself ...
i'm a looser. i learned something by having someone else show it to me. shame on me. what a crime!

i'm done with this "discussion".
if you ever run accross a mid' 80s honda dirtbike that uses a "Pro-Link"
progressive spring setup, take the time to go for a ride.
then turn the spring upside down and try again.
then come back here and tell me you didn't feel any difference ...

until then, i'm sticking to what i know works.
(IMG:http://www.914world.com/bbs2/html/emoticons/wavey.gif) Andy

[Aaron Cox]

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and cut!

[slivel]

I run progesssive springs. Not a single spring but a linear rate spring stacked on top of a progressive rate spring. The progressive rate spring is designed to go into coil bind. I run the heavier linear rate sping on top because I want less unsprung weight near the major moving axis. This is not because I believe that there is any difference in overall spring rate with one or the other spring on top - there is not. However due to the slight difference in the unsprung weight there MAY be a difference in road feel. YMMV.

[messix]

tastes great <> less filling