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Discussion Starter #1 (Edited)
Has anyone measured their motion ratios?

I'm looking for conformation on the front and rear motion ratios for the Kappa suspension. I have a 2008 Saturn Sky LE5 and measured the front and rear MR's to be .73 and .68 respectively.

Attached are the pictures of my measurement apparatus.


 

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Pardon my ignorance, but what is the "motion ratio"?
 

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Pardon my ignorance, but what is the "motion ratio"?
The motion ratio is the shock/spring travel divided by the wheel travel. That's a bit overly simplified, but it describes the relationship between the wheel travel vs. coil over travel for the Kappa platform.
 

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He's talking about the relationship the wheel travel has to suspension travel, usually 0 point something. Not sure why though as other than an academic exercise it doesn't really get you anything.
 

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Ummm....wouldn't it be easier to use the formula for a triagle? It seems like that's a lot of work for something that could yeild you something very close just by measuring 2 of the 3 sides.... Just my opinion....
 

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Ummm....wouldn't it be easier to use the formula for a triagle? It seems like that's a lot of work for something that could yeild you something very close just by measuring 2 of the 3 sides.... Just my opinion....
I approached the problem as you suggested, sort of, by measuring the installation angle of the coilover and the pivot points of the coilovers and the lower A-arm ball joint. I thought this would produce the same numbers or very close but it didn't. :huh:

When I calculated the motion ratios (MR) using the above apparatus I was impressed with the accuracy of the results. I collected 10 data points from both the front and rear corners and used a spreadsheet (Numbers) to plot the data on a graph. Both corners produced straight lines. :yay: Using the linear regression function of the spreadsheet the equations for the lines were determined and the slopes of these lines are the MR numbers. One of the cool things about the linear regression function is that it will also give you a R^2 value that indicates the accuracy of the curve fit. A R^2 value of 1 is a perfect fit. The R^2 value for the data I collected and the equations for the lines is .9999 !!!! A near perfect fit. :woo:
 
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