looking for a formula for finding wheel rate

[sunny311]

Here's what i have a triangulated 4 link setup on a truck. Variable rate air springs mounted outboard the frame, on the lower link bars. The bars are 38" long and the spring is mounted 10" from the frame pivot and 28" from axle pivot. My question is how can i figure out the spring rate at the wheel. I know it's not a constant rate, and it doesn't matter much since the pressures will most likely be changed while i'm riding. But i'm extremely curious. Any help would be greatly appreciated.

T

 

[GregLocock]

Draw the suspension at design. Raise the wheel by y inches (say 1) and draw it in the new position with the body fixed.

Measure the difference in length of the spring. call this x. x/y is the motion ratio of the spring.

The additional force in the spring is R*x where R is the rate.

The proportion of the load that gets to the wheel is R*x^2/y

So the wheel rate is R*x^2/y^2

Cheers

Greg Locock

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