Progressive VS Linear Rate Springs, ed ju cate me.... Options

[Aaron Cox]

i have opinions of both.....

i run linear 140's..... a friend of mine has progressive 165's.

what are the pros and cons of each.

[MattR]

im not your friend

[rick 918-S]

QUOTE (MattR @ Feb 8 2005, 10:01 PM)

im not your friend

(IMG:http://www.914world.com/bbs2/html/emoticons/happy11.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/w00t.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/lol2.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/happy11.gif)

[MattR]

(IMG:http://www.914world.com/bbs2/html/emoticons/rolleyes.gif) dont get all emotional aaron.


okay, so my understanding is progressive springs apply an exponential force rather then a linear force. Basically the spring constant changes during load. So when you're in a turn, instead of bottoming out the suspension, you're adding more spring rate. The advantage is the car is smoother and doesnt oscillate when there is no significant load on the suspension, but under load (in a turn) the suspension stiffens up.

[nebreitling]

do you like your spring rates -- and therefore handling -- to change as you dive deeper into a turn?

then progressives are for you.



linear all the way...

[Aaron Cox]

but the exponential curve of the spring rate isnt easy to predict..... unpredictable corner load = unpredictable handling

QUOTE

do you like your spring rates -- and therefore handling -- to change as you dive deeper into a turn? then progressives are for you. linear all the way..

EDIT: thats right, power to nate dog!

[MattR]

Well dont your forces increase as the tire patch is taken toward the limit? There is nothing linear about a tire patch, or body roll, or slip angles. Those are all exponential functions, so why arent your springs?

[Aaron Cox]

body roll with progressive springs in exponential....

body roll with linear springs is linear (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)

[MattR]

you have a sway bar, right? a big ass tarret one. That is most definatly not a linear progression.

[nebreitling]

i don't know how much all this exponential vs. linear stuff sums up the argument. i'm totally willing to concede that *everything* is exponential....

but, in my very humble experience (ie. driving only 1 914 w/ progressives vs my linears), validated by people who have forgotten more than i'll ever know, driving a car at the limit is more predictable on linears...

look at generic race springs: all linear.

[Aaron Cox]

QUOTE (MattR @ Feb 8 2005, 11:15 PM)

you have a sway bar, right?  a big ass tarret one.  That is most definatly not a linear progression.

its a torsion bar..... thats all it is.... effective spring rate doesnt change....

and i have no body roll (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

[Brett W]

Progressive rate springs are springs that get stiffer per inch of compression. They tend to be nice for squishy production cars that like a nice ride but need to keep from knocking the mirrors off if any hard conering occurs. They give a very good response to mild frequency bumps. Making for a nice ride on rough streets.

For a performance car stick with straight rate (linear) springs. they will have the same characteristics throughout the range of motion. Your car will take a predictable set in the corners as opposed to rolling a lot and then settling down on the heavier rates.

Linear rates will tend to act like rising rate springs due to some mounting considerations. When the spring is mounted directly over the axle and axle travel is purely vertical you get a linear rate. But when Motion ratios are introduced, when the wheel moves at one rate and the springs operate at another, you in effect create a variable rate spring. Variable rate springs can bring another variable into suspension tuning, which is very hard to deal with.

Coil springs and leaf springs are the only ones that lend themselves to rising rates. In our case coils are the only ones to be concerned with.

[John]

My opinion about the progressive coil springs is that for the first amount of travel, the spring is softer than the last amount of travel.

I had a set of "progressive" springs and didn't like the way the car reacted. The first inch or so of travel was soft and became progressively firmer just like I would expect, but I didn't like the fact that you had to "set" the car before it would really feel stable.

I went to linear springs and like it much better. The first inch of travel is almost just like the last. (good to the last drop) (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

I think that the way they make those progressive springs is that the "soft" part of the spring has the coils spaced further apart, while the "firmer" portion has the coils spaced closer together. (that might be backwards.....)

In any event, I don't like the variable spring rates in a performance application.

On bumpy streets, however, it might be a good thing.

[lapuwali]

Pretty much, that's it. You can run a softer initial spring rate, but a compressed rate that's stiff enough to prevent bottoming. Note that linear rate springs don't always translate to a linear spring rate at the wheel. If the spring axis is tilted significantly wrt the plane of suspension movement, the rate will naturally change as the suspension compresses. On the 914, the axis of the spring is more or less in line with suspension movement, so the rate is reasonably linear (on the rear, of course).

Gas-charged dampers also often provide some springing action in compression, so the damper also has to be factored in when discussing wheel spring rate. This rate is always exponential. There have been "dampers" which had air or nitrogen cells in them that provided 100% of the springing. Rubber springs also provide a non-linear springing effect, and quite a few cars rely on compliant bumpstops when cornering to provide some springing.

It's not at all difficult to get used to spring rates that "change" mid-corner. As noted, the tires (which are also part of the spring system, and being pneumatic, are exponential springs) provide a significant spring effect.

In short, pure linear springs do not exist on real-world cars.

[MattR]

Squishy for production cars? Cars create oscillations that unsettle the car. If your car is sprung too tightly ( (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif) ) it will literally bounce under acceleration and at the top of the sin curve it will lose an amount of grip that is proportional to the amplitude of the oscillation.

[lapuwali]

QUOTE (nebreitling @ Feb 8 2005, 10:16 PM)

look at generic race springs: all linear.

Horses for courses. To some extent, it's a "feel" thing, and some people like non-linear springs, even in racing applications. Racing applications don't dictate everything I do, and shouldn't for you, even on the AX course. Road-racing is the not the same as AX, which isn't the same as street driving, as I'm sure you know.

[MattR]

QUOTE (nebreitling @ Feb 8 2005, 10:16 PM)

look at generic race springs: all linear.

is that really true? how can i verify that?

[nebreitling]

QUOTE (lapuwali @ Feb 8 2005, 10:24 PM)

QUOTE (nebreitling @ Feb 8 2005, 10:16 PM) look at generic race springs:  all linear. Horses for courses. To some extent, it's a "feel" thing, and some people like non-linear springs, even in racing applications.

point conceded.

[Aaron Cox]

for street: gimme progressives..... nice ride

for AX: gimme something that is predictable in corners...... always the same throughout the corner.....

[Aaron Cox]

QUOTE (nebreitling @ Feb 8 2005, 11:27 PM)

QUOTE (lapuwali @ Feb 8 2005, 10:24 PM) QUOTE (nebreitling @ Feb 8 2005, 10:16 PM) look at generic race springs:  all linear. Horses for courses. To some extent, it's a "feel" thing, and some people like non-linear springs, even in racing applications. point conceded.

comes down to feel (IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)