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Chat with a Lotus technician

5K views 56 replies 25 participants last post by  khamai 
I'm surprised at how small the difference in spring rates is. And I agree with John, a 10% increase doesn't sound like much, no matter how you slice it. I'm daily driving a car with spring rates almost 200% higher than stock. Sure, it's starting from a different basis, but judging from the numbers, by my standards I don't expect a rough ride from the LSS.
 
How a spring acts depends on where it is attached, and the angle. Imagine that the lower end of the spring is attached to the middle of the suspension arm. In that case, the spring will be compressed 0.5" if the wheel moves up 1". This means that you have a motion ratio of 0.5.

To quote Fred Puhn: "First, the stiffness of a suspension is not the stiffness of the spring all by itself. The important stiffness is that seen by the wheel or the body, which may be different on account of leverage." He uses the example above, and for an 800lb/in spring in the middle of the suspension arm, the vertical stiffness is 200lb/in. In the general case, you multiply by the motion ratio squared (Puhn uses the term "mechanical advantage" for the inverse of the motion ratio).

Edited for correct definition of motion ratio, see http://www.rc10.com/racerhub/techhelp/marc/Handling.5.html.
 
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