i am preparing to order custom rate GC/Eibach springs for 96 coupe w/ b16, spring rates to be determined (400f/400+r). since GC offers to make custom springs any rate, any length, i was curious whether longer springs (by as much as one inch) would be advantageous.

when set up for street my car rides at a realistic ride height - barely halfway down the GC collars, almost a full two inches to spare. when on road course, i go just a few turns lower than that.

what i'm getting at, is that if i have more than an inch to spare on the collars, would it be advantageous to get a taller spring? i don't think it would allow for more travel, as lowering the perch would cancel out the longer spring, but is there another advantage i am not thinking of?

 

There's less chance of coil-binding if you use a longer spring. If two springs have the same spring rate but one is one inch longer, it will take more force to compress the one inch longer spring. Therefore lessening the chance of coil-binding. Other factors come into play also, but that's the basics.

Edit: Instead of buying 400lb/in springs front and rear, why don't you go something like 400lb/in springs for the front and 500lb/in springs for the rear? That way you can swap springs later on if you decide to.

 

i am still undecided as to rear spring rate - it will be at least 400, most likely closer to 500 like you said (that's what i meant by 400+).

i'm getting ahead of myself (blame the captain) but, check this out:

http://www.efunda.com/designst...k.cfm

this is really pushing it for this late at night, but bear with me. if you insert a constant spring rate (400), a constant force (500), a given length (12 for simplicity), you end up with a deformed length (let's say coil bind) of 10.75. if you keep force & spring rate the same, change free length to 13, deformed length becomes 11.75, or, if you're not keeping up, once inch more than before. doesn't that mean that, in layman's terms, coil bind remains the same for a given spring rate with a constant load, as you change the height of spring?

i know there is someone here that is way more qualified to answer this question. will that person please step forward...

edit - sorry that website only lets you mess wiht it once, the requires you to sign up or some crap. what it said was this...

k=spring rate
f=force
l=length of spring
l(def)=length of spring deformed

k=f/l-l(def)

 

the deformed length is _not_ the length at coil bind. if you goto http://www.ground-control.com and click on catalogues, then the eibach spring catalogue you can get all the numbers for the springs. in short though:

a 2.5"ID 7" Free Length 400lb spring can be compressed 4.29" before going into coil bind. The force required to compress the spring that much is 1711lbs.

a 2.5"ID 8" Free Length 400lb spring can be compressed 4.76" before going into coil bind. The force required to compress the spring that much is 1905lbs.

as you can see, increasing the length of the spring 1" increased the amount you can compress the spring by a little less then .5" and the force required to bind the spring by nearly 200lbs.

spend some time on ground-control's and eibach's websites. there is a lot of info. to be gleaned from there.

nate

 

wouldnt it make it harder for u to raise and lower the car with the longer spring? id think u may be trying to go against the spring when raising the car back to your street ride height.
-spenc----who thinks the gc's should have a dam wrench

 

Edit: misunderstood someone

500lb/in is where I will go with my rears when I get around to it, but that may not be streetable for some...


Modified by GSpeedR at 7:34 PM 5/22/2003

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GSpeedR &raquo;</TD></TR><TR><TD CLASS="quote">

You mean compress the spring to coil bind, right? As two springs with the same rate (nomatter the length) require the same force to compress them 1" (so long as coil bind doesn't occur).

500lb/in is where I will go with my rears when I get around to it, but that may not be streetable for some...</TD></TR></TABLE>

Yes, that is what i mean/what i said. I did say coil-bind in the beginning of my paragraph.

Edit: Also read Solo-x statement up above about requiring more FORCE to compress the spring to coil-bind with the increase of spring free length.