Effect of Left Front Spring Rate on Roll Stiffness in a Left-Turn-Only Car with ARB

I'm trying to better understand how the left front spring rate affects roll stiffness calculations for a left-turn-only car equipped with an anti-roll bar (ARB).

In a left turn, most of the load shifts to the right side, compressing the right spring. This compression also twists the ARB, which in turn acts on and compresses the left spring.

• How does a stiffer / softer left spring influence the overall roll stiffness?
• When increasing stiffness of the left spring, presumably the ARB twists more to compensate and increases the roll stiffness?
• Should the left spring rate be factored into roll stiffness calculations for the front axle, or should it be ignored in favor of the right spring rate (since it bears most of the load)?

A stiffer left front should loosen the entry up and opposite for a softer spring. A stiffer left front will produce more roll angle to the right and more load on the ARB which is why softer spring setups require a stiffer ARB. The front springs and ARB contributes to the overall roll angle/stiffness. So it should be included in calculating roll stiffness especially if you preload the bar. The ARB also try’s to pull the left front up, not compressing the left front due to the right front compressing and pushing the bar upwards. I hope this helps some?

> The ARB also try’s to pull the left front up, not compressing the left front due to the right front compressing and pushing the bar upwards

Hello Jacob, thanks for the response. What do you mean by “pull the left front up”? Perhaps I’m misunderstanding ARB mechanics, but for example, if I had a super stiff bar with no flex arms, wouldn’t the RF compression go all the way through the bar / arms to the LF and compress the LF spring effectively lowering the left front frame ride height, hence the reduction in roll?

You would be correct about that. I interpreted what you said incorrectly. So yes, it would try to compress the left front spring by pulling upwards on the left arb linkage since the arb is usually attached on the right side which under compression would push upward on the bar.

This question is stemming from the HP Academy LLTD Worksheet. The input for Elastic Stiffness front values is Front Spring Stiffness and Front ARB Stiffness. If we make the assumption that we are calculating for a left-turn-only car, how would you factor in the affect of the LF spring? I'm using the RF spring rate as the input value for Front Spring Stiffness, but after thinking about it, that seems to be missing a significant factor that the LF spring is contributing to the overall front stiffness.

Any insight on calculating and including LF spring's roll stiffness contribution -- thinking you'd need to do something like: (LF spring rate / motion_ratio ^ 2) and then adjust that with some kind of an ARB twist fudge factor? Or maybe just simply tweak the Front Spring Stiffness input value with an educated guess on a combined / adjusted RF and LF spring rate?