motion ratio help

[stanglou]

am i hearing this right, the motion ratio is



distance from LCA inner pivot to lower shock pivot/length of lower armX2

I know that you should try to get the shock as parallel to the arm as you can, and as far out as you can, but i was also confused about the spring motion ratio(66 mustang spring rides on upper arm) is that also a design factor? what isa good motion ratio for the shock and spring?

[wally8]

I believe you have to go out to the centerline of the tread for the last value, not just to the outer ball joint to get the total leverage.


Wally

[astroracer]

The leverage force is applied at the ball stud.
The tire/wheel is unsprung mass and is not used for this calculation.
Here is one of the calculators I use...
http://www.proshocks.com/calcs/imotion.htm
This will get you pretty close without running the suspension through a design program like Performance Trends...
I was wrong in my first post... The quotient should be Squared, not multiplied by 2... Sorry.
Mark

[astroracer]

am i hearing this right, the motion ratio is

distance from LCA inner pivot to lower shock pivot/length of lower armX2

I know that you should try to get the shock as parallel to the arm as you can, and as far out as you can, but i was also confused about the spring motion ratio(66 mustang spring rides on upper arm) is that also a design factor? what isa good motion ratio for the shock and spring?

I should have clarified. The "shock" in my equation is a coil-over shock so the motion ratio will apply equally to both pieces. A separate shock/spring will need the equation ran on both components and the numbers will differ accordingly although most separate shock spring applications are colinear so the single calc will still apply.
Mark

[wally8]

Thanks Mark. That makes sense now that I think about it more. I better go change my spreadsheet. That will teach me to blindly copy formulas without thinking through them first.


Wally