# Dynamic Spring Rate formula

#### bei77

Hi guys, I am trying to find a formula to calculate dynamic spring rate. Here is what I have to work with.
Spring rate: 200#
Static on the car: 1000#
Spring travel: 3"
Dynamic Load, car going through turns, 2200#

#### ChipB

PHF Helper
Not sure what you mean by "dynamic spring rate." If the spring is rated at 200 lb/in, that's what it is. Keep in mind that there are other components besides a spring that influence how much the car leans in a corner - for example anti-sway bars tie springs on both sides of the car together. But if the increased compression from a static 1000 pound load to a dynamic load of 2200 pounds is 3 inches, then the spring constant is (2200-1000)/3 = 400 pound/inch.

#### bei77

Hi Chip, maybe I didn't state the question correctly.

The spring rate is 200#, when I put it on the car and put the car on the scales the wheel weight at that time is 1000#.
When I use a machine, GaleForce, to compress the shock the 3" of travel that I have I get a reading of 2200#.

I was wondering, since I borrowed the GaleForce, if there was a way to calculate this without the machine.

Hope this clears the question up.
Thank you.

#### ChipB

PHF Helper
Does the Galeforce machine apply a load to the shock and associated spring only? Or does it apply a load to the car? If the latter - do you have the resulting weights for the other three wheels? I'm guessing that this is another type of corner balance problem. If it applies a load directly to the shock, then the compression of the spring would be impacted by the geometry of the suspension. So yes, I think it can be calculated if you can define the suspension geometry.

Last edited: