Technical front spring free arc

Hi, searched but did not find answer, getting ready to order chrome front springs and needed to know is free arc measured from top or bottom of spring to the center line of the 2 eye's ?

 

What kind of spring,car-year?

 

and also when measuring axle, do you measure from outside of king pins?

 

here it is

 

The arch is determined by the spring stiffness and weight supported. Shoot for 3 and maybe 4" of spring deflection when loaded. The spring will be loaded some by the shackles so say 6' free arch to the bottom of the spring. How much it will deflect depends on the weight and spring rate. Assume a weight of 800lbs sprung weight and a rate of 100 lbs/in for a nice ride would work 200 lbs/in for both sides of the spring times 4" deflection gives the load of 800 lbs. You can redo this with your numbers if I am off.

PS. You can look at a spring and tell if it can be made to ride gentile. A flat spring can't move much before it has used all it's arch. A spring with a lot of arch will have more movement so has a softer rate.

 

I think they are measured from the centers of the king pins. I put a tape in the hole and measure to the far side of the other hole.

 

the one's that I am interested in ordering say's the underside measurement is 4.75'', is that from the top of the leafs or from under the springs(I know should be common sense because of underside) but want to make sure, the cost of shipping back I would have to keep them.

 

I would contact the manufacturer and get more facts as to the rate and how the arch is measured. The rate can be figured if you know the number of leaves and how thick it is in the middle so you know the leaf thickness.