Quote:
Originally Posted by pothole
If the H&R coils are indeed a little thinner, does this more or less guarantee it's softer? Is coil thickness pretty much the be-all and end all?
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The coil spring rate is simply characterized by the thickness, number of active coils, and coil diameter. Because the basic spring rate characteristic is proportionally related to the
thickness to the fourth power, a very small increase in thickness will result in a significant increase in spring rate.
Quote:
Originally Posted by pothole
I also happen to have a left over custom made spring from my old BMW track day car and the comparison is quite amusing. The coil is miles thicker than either Porsche spring (and it's only a 450lb spring, which isn't that insane) and you can't bend it a mm by hand. I can squeeze the H&R spring and get quite a bit of deflection!
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The H&R spring is a variable rate spring - initially it is relatively soft (thus you can deflect it by hand) but then progressively stiffens as deflection increases (note the progressively increasing diameter of the size of the coil and the decrease in coil spacing). H&R does this to create a shorter spring that provides a reasonably smooth ride over small bumps (initial compression) but is stiff enough that the spring provides good support and avoids bottoming out over large bumps (middle to full compression).
H&R sport springs are intended to replace the stock springs while lowering the ride height - they are not intended to increase spring rate significantly over stock (but this does happen to some extent just because the springs ultimately have to be stiffer to provide approximately the same overall spring rate in a shorter spring.)