280ZX rear struts

[DC871F]

On 6/6/2018 at 12:41 AM, Zed Head said:

If you didn't use the same springs then you can't really say it's the shocks.

If you like the ride height of the car is it is now, with the old shocks, then the odds are in your favor if you take those same springs and put them on the KYB's.  You might get an extra 1/4 to 1/2" inch.  I'm sure that they're the same internal pressure as the KYB's we use on the 280Z's.  We get a little pop from the gas struts too.  Not 2" though. 

Installed the new KYB shocks with the older springs, and its now sits normal.

So the springs that came with the car have a different rate, but they look identical. Micrometer at my other shop, so once again, I'll check that at a later date.

Only explanation I can come up with, is that a long time ago this car had been wrecked in the rear, evidence of a new rear panel and a lot of body work in the rear of the car, which was done flawlesly. I can only speculate that they installed new strut asseblies and they were not factory.

Attached is the comparison before the swap.

[Zed Head]

Spring rate can also depend on the heat history and type of steel.  There's a bunch out there about it but here's a couple of links.  Plus the coil on the right looks like it's wound on a wider diameter so not the same manufacturer, probably. 

https://www.meadmetals.com/blog/types-of-metal-compared-infographic

https://www.precisionsteel.com/spring-steel

https://www.mw-ind.com/faq-items/what-is-the-difference-between-cold-winding-and-hot-winding-and-when-is-one-chosen-over-the-other/