While it's just temporary until I can afford a real suspension I'm trying cut springs and different spring options. Currently I'm running the normal 240z springs but I found a good set of 280z springs. Now I was told the 280z has a stiffer spring but it's a softer rate than the 240z, is that true? I was looking for a somewhat stiffer ride. I've looked around and haven't seen anything on this mostly 240z springs on 260's and 280's.

I think you will have to cut the 280 springs. They ride higher than the 240 I think. They aren't stiff either. Softer than what you have I think.

280z springs on 240z should lower it, at least according to a grass roots z racer told me.

I just took his word for it.

The 280Z springs are quite a bit stiffer - looks like you could cut a coil or 1 1/2 coils off.

As I recall the 280Z's sit higher because they have a taller isolator at the top of the strut.

<pre>

1977 280Z 240Z

FRONT

Spring Rate: 103 lb/in 83 lb/in

Free Length: 15.98 in 15.2 in

Active Coils: 9.5 8.5

REAR

Spring Rate: 127.7 103 lb/in

Free Length: 15.43 in 15.0 in

Active Coils: 8.5 9.5

</Pre>

FWIW,

Carl B.

Data I pulled from Zcar.com archives:

0.5" drop = cutting upper and lower coil

1.5" to 2" drop = cutting upper two coils or lower two coils (recommended)

2" to 2.5" drop = cutting upper 2 coils and lower coil

Its all about the isolater, I used a 280 isolator on my 73 when I changed the spring to even out the car. Factory rates are different but aftermaket are all the same except for the isolater.

Interesting. sorry for the incorrect info.

While it's just temporary until I can afford a real suspension I'm trying cut springs and different spring options. Currently I'm running the normal 240z springs but I found a good set of 280z springs. Now I was told the 280z has a stiffer spring but it's a softer rate than the 240z, is that true? I was looking for a somewhat stiffer ride. I've looked around and haven't seen anything on this mostly 240z springs on 260's and 280's.

280z springs are stiffer than a 240'z, I used the rear insulators from a 240z on my 280z and cut 1.5 coils at the top of the stock springs. Rides lower and more aggressive now.

Edited March 21, 201113 yr by johnnyt

Thank you everyone for the information it really helps.

Its all about the isolater, I used a 280 isolator on my 73 when I changed the spring to even out the car. Factory rates are different but aftermaket are all the same except for the isolater.

No, they are not. A little enlightenment is called for.

One thing to remember...quasi fictional example:

If a Z weighs 2400lbs and is 50/50 weight distribution then you have 600 lbs of weight on each wheel.

If a performance spring is rated 200lbs/ per inch and just fits in the strut without the need for a compressor then it will drop 3" (600lbs / 200lbs/inch) when loaded by the car.

If you have a stock spring that is 100 lbs/per inch that needs to be compressed 6" to fit in the strut then the car will not drop because the 6" of compression preloads the strut to 600lbs.

To properly pre-calculate drop you need:

Corner weights

Spring constant (lbs/inch)

Length of uncompressed spring

Length of spring in unloaded strut

If I had time I would love to collect this data for stock springs.

As mentioned above. Some of the 280z strut isolators are thicker and can lift the car slightly.

Wow those look like they could use a good cleaning.