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Discussion Starter #1
Hi guys... how do we calculate our spring rate at the Wheel for the Rear Springs?

For example 200-250 Rate Springs = What at the Wheel?

and 350 Rate Springs = What at the wheel?

Thanks!

Dave
 

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Multiply the spring rate by the square of the motion ratio. Dimensions in the Mathis book have the spring moving a tiny bit more than 70% as much as the axle pivot, so half would be a good number to use to get wheel rate. So 100 - 125 and 175 for your two springs. In two wheel bump mode, anyway.

Couple of things to keep in mind.

Angularity of the spring away from perpendicular to the arm has a small effect (cosine^2 of the angular deviation from perpendicular).

The wheel rate in roll also depends on how far apart the axle pivots of the LCA's are relative to the rear track. And like all the other dimensional stuff as it affects wheel rate calculations, you have to square this ratio too before applying it to the two wheel bump mode wheel rate above.

Norm
 

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Discussion Starter #3
Thanks! That is great info!!

I will use that rule of thumb...

What do you think that the Front Wheel Rate break down is? I have 850 Springs up there now.

Thanks
 

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Best info I could still find for the front is a M.R of 0.5 for OE type springs and 0.9 for C/O's. No info on whether any cosine function is included, though that would still be a rather small correction. You're probably within the range from 205 to 215 lb/in.

Norm
 
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