Custom Coilover Questions

[midnight brother]

Looking at the install page for 240sx.org, there is an article about making your own custom coilovers which got me thinking about making my own for my car. The person who made this article used linear rate springs, however ground control uses Eibach springs which are progressive.

Linear springs have a constant spring rate while progressive rise as the spring loads increase. Choosing the right linear spring rate would provide a good ride and harder rates would provide a stiff harsh ride. Progressive springs like Eibach are used for show / help suspension. If the progressive spring rate changes wouldn't this be worse than having a constant spring rate and make it very bumpy depending on the setting?

Ground Control however has made alot of kits for cars and I have heard positive feedback from AE86 people as well as Hyundai. Designing my own kit should I figure out what linear spring I should use or just use Eibach like ground control do? My thoughts with using the Eibach would it takes the guess work out of which spring is correct without having over / understeer problems.

Also is there a general rule of thumb as to how long of a threaded tube you should use or any way to know? No one I know has done a project like this where I can turn to and I doubt actual companies who do suspension would help me. I don't want to have too little of a threaded tube and not be able to adjust my springs but in the same sense I don't want to have to much and have coilbind and break something.

[midnight brother]

The install has enough information for the 240 but however designing this for a 93 Elantra there are variables to help determine numbers that I can't find such as oe spring rate, unspring, wheel freq, etc...which hopefully something should be in the manual when I check tomorrow.

Determining how long of a thread tube I thought would be how much suspension travel is left before coilbind, but the formula to get the number I don't know. I thought it would be just simple subtraction.. spring length - max stroke - static deflection = x, however the numbers don't match with what he used. He used 5 inch long and 2 inch wide for the front but I don't see anywhere why he choose that length unless im too drowsy right now.

2 Afco 12in, 175lbs/in 2-5/8in coil over springs (p/n 22160, 75$CND)

What does this 2-5/8in mean?

Thank you for your response K-Car.

[midnight brother]

If only it were that simple my friend, about 2 people total own a 93-95 and the rest don't give a damn. Thanks for posting and the help you have given.