I honestly don't know much about calculating spring rate or the effect of cut springs etc so I was hoping for some input.

When you cut front 3rd springs do you do it from the bottom or top? The reason I ask is that the springs I have both snapped and I am missing approximately 2/3 - 3/4 of a coil on each (at the bottom). I was just wondering if this would change the spring rate or if that is an inactive coil or something and maybe not really have an effect on rate? For whatever reason the ride height has not changed noticeably but the "new" end of the coil is outside the pocket at about 3 o'clock (if the pocket is at 12). Maybe ride height is unaffected because that portion of the perch is slightly higher than the pocket??

Any help would be appreciated,
thanks.

 

Anyone?

 

Crazy hawaiin would know this one.

I'm shocked you haven't gotten any response from anyone.

i'd say you'd normally want the cut part at the top.

sounds like you need new springs though.

 

I am surprised to as there are definitely some very knowledgeable suspension people here. I hope they chime in The problem is (besides not knowing how to calculate spring rate) I don't even know if that is an active or inactive coil down at the bottom that is missing so may not even affect spring rate

I agree though definitely need new ones. I like the ride though so that is why I am trying to figure out what rate it is (if it has changed) so I can better match.

 

oops- I meant to start a new thread

 

You cut it from the bottom. One end of the spring is flat and sitts up inside the can(left side). The other end is more pointy and sits into the channel index of the A-arm (right side)

You cut the right side or bottom.

If your springs a broken then just replace them completely. They are only going to cycle faster now and break even easier next time causing a catistophic failure and damage toyours and possibly other vehicle on the road when you stuff into the ground and loose control. If they are that corroded, then the bumpstops and fasteners are most likely on the verge of failure also.

 

Sorry guys, but I'm not the right guy to answer this one. I do know you're supposed to cut at the bottom (or pigtail end) as Dean has stated, but as far as calculating the new spring rates, not something I know how to do. I've run cut springs in the past but I didnt know what rate they were. It was always a trial and error type of thing, see how it feels and go from there. If I'm trying to tune the car in the sense that actual spring rates matter then I always buy new springs at the specified height and verified linear rate (I always go through suspension spring specialists). I've mentioned in past threads that in my opinion the average enthusiast does not have the equipment to properly calculate things like actual spring rates or dampener compression/rebound rates. Don't remember who replied but I think they said that there are math formulas you can do to calculate spring rates and its accurate. But I dunno what those math formulas are, sorry man. I think all this happened in the Weight Jack thread I started, but not sure. I say keep doing the research and if you can't find the answers then consider going by trial and error like I did. But you know on the other hand, Dean has a good point about the springs breaking. Its a sign that they are fatigued, I wouldnt trust them. If it were me I would trash em and buy new springs with verified rates. In any event, be sure to properly index whatever springs you install in the front (mistake I have made in the past, along with many others hehe)

 

Sorry, shoulda mentioned, I am definitely planning on replacing them after discovering they snapped, it is just I want to figure out if the rate has changed (since they are shorter) to know what rate to match them to (since I like the current ride quality/handling combination). I definitely don't want to go with a lower rate and hurt handling but I don't want to go crazy stiff either as I drive it a lot (and don't race). Oddly enough though, not sure how they snapped because what is left of them looks beautiful and not really corroded at all What do you mean by cycle faster though?

DRR - Do you know how to calculate spring rates? ANy idea how much it would have increased? I can get the info on the springs.

thanks guys.

 

Try this:

Spring Constant (k) Calculator and Formula -  Engineers Edge

 

Don't know what to put in for "G" though.

 

There is page on here somewhere that shows the rates of different coils from different manufacturers and shows also their freecoils and overall height. From what I recall the Eibach Sportline(I think its the Sportline. Its the one that doesn't lower as much actually has a higher rate than the lower Prokit- I could have this backwards between which is named Prokit and Sportline) anyways, has slightly small wire dia. than mine at something like .625 and 5 3/4 free coils and an overall height of 12.75" (they are rated at something like 708lbs @ 1" compression). Mine have a .700 wire and 4 3/4 freecoils and a free hieght of 12"(mine where 13" to start and 800lbs @ 1inch compression- non cut).

Now with that said, most factory springs are about 500-600range thereabouts. These spring above are getting stiffer and about 900-1000lbs would be considered roadracing rates for a 3rd gen. Note: I have 800lb plus on a lighter weight nosed V6 car- it is stiff springed.

Now as for cycling faster? The less free coils you have the faster the spring will cycle between the compression and recoil bounce (this is called "coil frequency")- Why?- because as the number of free or active coils in reduced, the rate goes up faster and faster as it compresses.

Heres an important note many do not understand on coilsprings. The less free coils you have the greater the need for a high rebound damper shock. Take a coil like mine, Once installed, those 4 3/4 free hieght active coils now compress slightly more and become only 4 1/2 free coil because of spring bind during compression to ride height. Now as the spring through travel motion does in fact lose even more active coil area and the outer coil section becomes more and more deadened against the nonactive upper and lower coils........So in conclusion, TWO different springs rated at 800lbs@ 1" compression will have different rates at 2" compression. Fewer active coils in a spring design increases the rate much faster. This is why you need very good roadrace quality shocks when cutting off coils on a spring design. Otherwise you get that dong, dong, dong, dong ride going down the road.
This is a picture of an Eibach Sportline (you can see in comparison to mine pictured above the difference in freecoils yet they are about near the same free height, this spring it tighter wound with less space between each coil which makes it a softer angle rate:

 

Shear modulus - Wikipedia, the free encyclopedia

If you dont get a realistic number, make sure you are using the correct units.
Just a wild guess, but from what I have heard in the past you're looking at ~100#/in increase or thereabouts.

BTW you should be able to get rid of a bunch of excess in the formula by making cancellations from each side (set it up as a ratio of x spring to y spring) and figure out what the % difference is based on the difference in height and coils. So... that constant you are asking for should just disappear anyway. That may not make sense to you, its kinda hard to explain or at least I cant think of a way. lol.

 

Ok, now I am definitely confused. I thought with linear springs the rate increase the same (ie. 500lbs at 1", 1000lbs at 2", 1500lbs at 3" etc), and with progressive springs the rate changes as it compresses more? Sorry, like i said I am green with this stuff

How much did you trim off your 800's and how much did that increase the rate out of curiosity??

thanks.

 

Look up Hooke's law.

 

In English lb and inch units, the range from about 11,000,000 up to perhaps 11,500,000 covers most steels.

Norm