Coil Spring Rate Comparison

[CpnJack]

I have two sets of coil springs that when fully extended are the same length. One set that came as 4.5" XJ lift springs from Rusty's has one more coil than the other set. I bought the second set expecting them to be a little taller because they were from a 5.5" lift for a TJ, dont know the brand.

Is it possible to say which set is preferred just by knowing that they are the same uncompressed length but one has an extral coil? I was trying think of a way to rig up a basic Harbor freight press to get a relative comparison of spring rates. Any ideas? I'm trying to pick the stiffer spring for ride height and plans on adding a winch.

[GMGuy]

Free height won't tell you much. A longer soft spring is going to compress more for a given weight than a shorter higher rate spring.

The number of coils isn't going to be much of a tell tale either.

However, wire thickness may, the thicker the wire, the higher the spring rate.
Your best bet is to rig up a patty stacker for the spring and drop a few hundred pounds* on it and see which gives you what you want.

*make sure the spring is contained.
*jack your jeep up with it** and measure spring height when the tire(s) leave the ground. Obviously the spring that compresses the least is the higher rate spring.

**make damn sure that spring ain't going to go flying.

Alex.

[CpnJack]

Thanks for the advice. I didn't want to use the jeep as weight because to do it safely it seemed like it would have been the same amount of work as just installing the springs and seeing how it sat. I did try stacking some free weight on them and it would have worked had I spent more time rigging it up.

I ended up putting a strut compresser on each coil, compressed both an inch then used a torque wrench to compare the torque to tighten the compressers another turn. The spring with one less coil (even though the coil count prob isn't the key factor) turned out to be stiffer. Once installed it looks like this set of springs is a little taller than the ones I had been using from Rusty's. Or, it could just be wishful thinking.

[GMGuy]

re coil count:
Heres an example for a *stock* passenger car spring application.
spring 1: 200lb/in 8.8 coils(.656")
spring 2: 165lb/in 9.1 coils(.625")

I like the idea of using a torque wrench on it for a quick and dirty check.

Alex.