The formula as I've used it:

Percentage of Front Roll Bias: Front Roll Couple / (Front Roll Couple + Rear Roll Couple)

Front Roll Couple = (Torsion bar wheel rate * 2) + rear sway bar wheel rate
Rear Roll Couple = (Leaf Spring wheel rate * 2) + rear sway bar wheel rate

Torsion Bar wheel rate = listed rate
Front Sway Bar wheel rate Opt 1 = rate as quoted from Hellwig or Hotchkis
Front Sway Bar wheel rate Opt 2 = sway bar rate * (Motion Ratio^2)
Motion Ratio: (sway bar attachment point from pivot point) / (ball joint from pivot point)
Leaf spring wheel rate = (listed rate) * ((leaf spring width / track width)^2) * 2
Rear Sway Bar wheel rate Opt 1 = *not sure if Hellwig & Hotchkis quoted numbers are wheel rate or sway bar rate - will need to measure and calculate old way*
Rear Sway Bar wheel rate Opt 2 = sway bar rate * (sway bar end link width / track width)^2

solid sway bar rate = 500,000D^4 / (0.4244*A^2*B + 0.2264*C^3)
A = Main bar centerline to end link - 90* (think ~8.5")
B = Main bar width (think ~30")
C = Main bar centerline to end link - at whatever angle the bar is (think ~10")
D = Main bar diameter (think 1.25)
*if bar is hollow, calculate rate for solid of that size, then subtract rate of a bar that would be the diameter of the hollow diameter
*sway bar rate formula from the Fred Puhn book - How To Make Your Car Handle.

Further credit to TC@HP2 - we've had a few email conversations about the theoretical handling line. There was even some discussion of making an excel for everyone to use, but we never did. Maybe TC@HP2 will still do that?


If you're serious about doing some of the number crunching on your own, you should look at getting the following:
-How to Make Your Car Handle - Fred Puhn
-How to Build the Ultimate Super Street Mopar - Mike Martin
-Mopar Oval Track book - I think the Mopar Oval Track Modifications book (available at Mancini)


Still, at the end of the day, the above formulas will only get you close. Be prepared to fine tune the combo (i.e. - buy more springs, sway bars, etc). If you work with Ron Sutton or one of the newer suspension setup programs that requires more inputs, then you can probably nail setup from the start. Those programs or Ron will require measurements every attachment point in your suspension.