four_by_nut said:

**OK. So let's rework that.**

Let's assume the following:

1) 4" Superlift springs in Wrangler length (D=49")

2) H is at 36" sitting on 38" tires

3) E is 18.5 (Tire radius loaded) + 4 (4" lift over flat stock) + 5 (spring eyes above main spring and spring perch and 1/2 of axle tube diameter) = 27.5"

4) L is 95" (Stock Wrangler)

AS for 4" springs = (49*36)/(27.5*95)*100%=68%

AS for stock springs = (49*36)/(23.5*95)*100%=79%

So.............the more arch, the lower the antisquat???

One comment on the tire diameter increase and CG relation. This shows that the CG is going to increase at the same rate as the roll center increases (1/2 the diameter increase). So the AS stays the same reguardless of the tire diameter increase. Right?

So are we getting anywhere?

Thanks for the clarity here. This really does help me to completely understand the relations involved.

I hope you folks can help me (this topic is interesting, and I am never too old to learn something new)?

I imagine the equation quoted is from Milliken (what is the reference source)?

Did this equation come with any basis for application (initial design conditions)? What I am interested in is what the author assumes for the design basis and/or other conditions that must be met to apply the equation properly?

On the question of more arch providing more anti-squat? Given the equation, and only a change in spring arch with the spring eyes parallel to the ground, yes. This change placed into the equation assumes the shackle length is not lengthened to allow the longer spring to work, or the shackle is lengthened but the eye height is compensated for by raising the shackle mount to (re)level the rear spring eye. These are ideal restraints to allow the equation to remain valid (not very realistic).

Back to your question. Old 60's era drag racers employed high arch leaf packs to reduce the AS% (they also leveled the spring eyes by raising the front end an equal amount -- the early high boy Gasser look demanded by factory mount rule restraints). When they started to rake the chassis for aerodynamic efficiency they had to learn better ways to get a leaf to hook up (one reason why I ask the initial conditions demanded for using the equation). The same sort of rules regulating leaf mount changes in Modified Stock crawling competition make this topic a worthwhile exploration.

Oh, and a change in tire size will slightly change the AS produced by the equation (a small decrease in AS for an increase in tire height, and the resulting increase in CG height). Spreadsheet the equation and play around some to search the results of changing one or another factor. This makes it easy to plug in the respective increase in H&E for a larger tire, and watch the resulting change.

Leafs may suck, and revolvers may suck, but some competitors are limited to leafs, so is it preferred to dismiss leaf design questions because the basic design limitations (well

) suck ?

Happy Trails!