Outer Limits 4x4 Board

I know this is revelant to all 4bs with leaves and not just zooks.

Does anyone know what is the relative difference between using a longer spring and more flex. How much do you gain flex / travel wise by placing x length springs in.

For example 4" longer springs, would you expect 4" more downtravel? Assuming no shocks attached and the right shackles fitted.

thanks

Nic

i think you'll find its more complex than that as it has alot to do with shackel length and the over all spring rate, even weather or not the second leaf is wrapped around the first (think its called military wrap).

Hmm, forgot about those things. Assuming all the same and only the length changes? and poss maybe a 2" shackle extension

any ideas

Bump

Been a long time since I looked at the equations, but there are 3 factors that make longer springs better.

(1) A longer spring will have less radius of curvature for a given amount of wheel travel than a shorter spring.

(2) A longer spring made from the same number of leaves and leaf thicknesses as a short spring will have a lower spring rate and therefore flex more (and more easily)

(3) A longer spring will have less torsional twist per unit lenth for the same amount of wheel travel than a shorter spring.

So it really comes down to the specifications of the new spring compared to the old one that determines how much extra flex you will have (assuming spring flex not shackles, shocks, etc are the limiting factor to travel).

If you put in a shorter spring that has the same number and thickness leaves as the old one, your extra travel will be mostly from (2). If you put in a longer spring with the same rate as before, your extra travel will be from (1) and (3).

It is difficult to give actual numbers for the amount of increase without having specs for the two sets of springs. If you have an engineering background then get hold of the "Automotive Leaf Spring Design Manual" published by the SAE. It has all the equations you need to work out the differences.

I was more just after a general info and opinions. But great info you have posted up.

Some good insight.

cheers

Assuming you are not shifting spring mounts, and are just using longer springs to gain more lift, then each extra inch of leaf length will give you ROUGHLY 2 inches of lift.
I base this on what I did. A set of springs about 2 inches longer than standard (eye to eye) reset to retain the original shackle angle, gave me about a 4 inch spring lift.