therealtime

I have been doing some research lately regarding inexpensive suspension setups. It seems that there have been alot of uninformed decisions regarding modifications to springs. I would like to try to help by simply providing a little more information.

It seems to be a popular opinion that cutting stock springs is a bad idea. Many people say it is bad because they speak from experience. The truth is that there is an acceptable range for anything. The following calculations are based on my own measurements of several springs and on the spring rate calculator I found at racingsuspensionproducts.com.
I am a mechanical engineer and I know that there is an equation for determining the rate of a coil spring based on the wire diameter, the average spring diameter (inside+wire dia), and the number of active coils. The first coil on each end sits against the spring perch and does nothing to hold the weight of the vehicle and is therefore inactive.

I realize that Honda springs are slightly tapered at the bottom which yields a "progressive rate", but there is minimal taper, and a minimal effect on the calcuilation.

My first consideration was a stock 99 Integra LS front spring with roughly 3.75in OD, .475 wire diameter, and 10 active coils. This comes out to be around 208 lbs/in spring rate. If you were to cut 1 coil off the top, the rate changes to 231 lbs/in and the height would drop around 1 inch. This change would have a minimal effect on ride quality and slightly improve the handling of a lightly modified or otherwise stock car. 2 coils off increases the rate again, to 260 lbs/in. 3 coils ups it to 297 lbs/in.

Remember that lowering the vehicle this much will destroy the alignment and change the roll center by changing the suspension geometry. Lowering the vehicle excessively also reduces the damper travel and can lead to premature failure of the seals or bent rods when the vehicle bottoms out.

For reference, I also purchased a set of "eBay coilovers" with cheap springs and adjustable perches. This whole set with adjusting wrenches was around $40 shipped to my door. I am sure that many of the eBay coilovers are different, but these springs only have 4.5 active coils. With a wire diameter .481 and an OD close to 3.5 inch, that makes a spring rate of 621 lbs/in! I'm not interested in riding a wooden rollercoaster every day, so I am not installing these on my car (I only bought the kit because I need the wrenches).

Conclusion: if I were going to lower my car 1-1.5inches, I would definately consider cutting stock springs. I can buy Integra springs off Craigslist for $20 to cut and keep my stock Del Sol springs in case I am unhappy. If I were going to lower my car more than that I would buy aftermarket springs and dampers designed for lowering.

Hope this helps someone.
-Tony

JDM_SOHC

I precisely measured & cut mine 2 years ago an my car handled fine with KYB struts and skunk2 camber kit for the whole time I had my car before it got jacked.. I actually would get compliments on my cars ride haha..

vtechjunkie

iTrader: (2)

That is a huge post. LONG WINDED!

D Griff

Great post, thanks!

It's long winded because he is giving a good explanation, describing the research he did on the subject. He's an engineer!

I might consider doing this, at least temporarily until I can afford the springs I want.

therealtime

I appologize for the essay. I wanted to cover as many questions as I could think of in the initial post so people could find the information easily, rather than have questions and answers on page 27 of a ridiculously long thread and no one be able to find them.

nix94delsol

i used the ebay coils on the front of my car and cut eibach in the back of my del sol. It rode like my moms volvo s60

werdupEGs

Great post!

Cut springs are deff frowned upon but when you get it down to a science like you have it should be considered a viable option.

AliGhanizad

ya thanx for the link bro, had seen dis thread once. But isnt there some kinda dampers/shocks for the ebay springs that cost the same as the springs too, .

Can u tell me the cheapest possible option, i mean abt 35buck for the springs and how much for the cheapest shocks.

And ya if i put ebay springs on stock shocks and compromise with the bounce, for hw long will d shocks keep up before blowing?>