Originally Posted By cataclysm80
Originally Posted By cataclysm80

OK, I have another question about one of the formulas.
"Front Roll Couple = (Torsion bar wheel rate * 2) + front sway bar wheel rate"

I see that it's torsion bar wheel rate times 2.
I imagine that's because there are two torsion bars & two wheels.
That makes sense.

I see that it's front sway bar wheel rate.
That's the sway bar rate for a single front wheel.

Since there are two front wheels, should it be front sway bar wheel rate times 2?




Front Sway Bar wheel rate Opt 2 = sway bar rate * (Motion Ratio^2)
Leaf spring wheel rate = (listed rate) * (Motion Ratio^2) * 2


These two formulas are both supposed to determine the wheel rate.
They both have spring rate times motion ratio squared.
Yet one of the formulas has a x2, and the other doesn't.
Why aren't these formulas the same if they're doing the same thing?

It seems like the *2 at the end of the Leaf Spring Wheel Rate Formula shouldn't be there.

Using 70 B body as an example, distance between leaf spring perches is 44 inches, divided by track width of 59.2 inches = .7432432 motion ratio.
that motion ratio squared is .5524104
multiplied by a 160 pound spring rate = 88.38566
then when you multiply that by 2, you get 176.77132
It seems odd that the wheel rate would be higher than the spring rate.


Couple things going on here.

First quote; No, you would not double the sway bar rate calculations because the sway bar works over its whole length. The sway bar interacts between both wheels so its motion ratio calculated rate will link the two wheels. Its not isolated to a single wheel.

Second quote; Yes, they are both calculating wheel rate, but they are two different components, so the rate is achieved in different calculations. In this case, the spring must be doubled, because the original formula was to determine total roll couple, not isolated spring rate. Since you clipped it out of context of the rest of the formulas, the *2 appears to double the spring rate for a single spring. Rather it is doubling the spring rate in the overall picture of the whole rear roll rate of two springs and a single anti-roll bar. So, you have 176.77# for the two leaf spring rates. You now need motion ratio adjusted sway bar rates to know the total rear roll couple rate.