Anti Roll Bar vs Springs; what’s a good balance?

Given that Anti Roll Bars do to some level impact the independence of the suspension of the opposing wheel, what is a good way to know what too much anti roll bar stiffness is? In the context of a track car where comfort is not a priority, would running stiffer springs and softer anti roll bars offer better suspension performance? As with all things I’m sure the answer is “it depends” and the answer is some kind of balance, however I’d love to get some perspective on how to determine what the best balance between springs/antiroll bars and which to prioritize for suspension set up for a track car.

We've run sports racers Stohr DSR / P1 / P2 with no anti-roll bars (ARB), and they have amazing grip! Formula V often runs with a zero-roll rear suspension to maximize grip (no ARB, and only a single spring for overall bump).

So I tend to think the ARB is just a trim tool (and cockpit adjustable at at least one end), and in general stiffer springs to reduce body roll is preferred to increasing the ARB if the goal is roll control or limiting suspension travel.

If you have an inventory of springs in 100 lb/in increments, then ARB setups that provide the equivalent support as 200 lbs spring range seems about right. If you reach the end of ARB adjustment, you just change to the next spring rate.

Thanks David! That’s helpful perspective. I hadn’t thought about the ARB equivalent to spring ranges. That’s a great point. Based on the course I was thinking about trying to run the softest ARBs I can and this gives me an idea of how to think about what the right amount of ARB is. I just installed some SPL LCAs with various mounting positions for the dampener, so I’m interested in using the lower motion ratio mounting point to stiffen the rear while reducing the sway bar stiffness to maintain roughly the same LLTD while giving the rear of the car more independent movement. I’d appreciate your feedback if you think I’m going in the wrong direction. Thanks again for the response!

The disadvantage of a lower motion ratio is that the damper moves less, so removing the ability to do damper tuning (if the are adjustable). I had a sports racer with a horrible .53 motion ratio in the front, and I ran like 2000 lb/in springs just to get a reasonable wheel rate in the front (aero car). Didn't matter what I did with the damper settings.... Modifying the front suspension design to get .78 motion ratio transformed the car...

You anticipated my next question 😂! I was just thinking through what the downside might be. I’m just running OEM suspension points on a 2011 STI that’s lowered 20mm. I do have two way adjustable dampeners, but the difference in motion ratio would be going from 1.25 in the rear to 1.20. Correct me if I’m wrong, but I don’t think it will negatively impact my dampening range to a significant degree. I’m not running any aero, so I’m all mechanical grip. The dampeners are running around the middle of their total range right now. I run a 24mm ARB up front (hard setting) and 22mm ARB (medium setting) in the rear. Most people seem to run bigger bars on this platform, but I don’t feel like I need it. (I’m also a total amateur so I’m not ruling out me being completely wrong as an option 😂). My springs are near perfect for my target wheel frequency, so I want to try sticking with smaller ARBs. However, I don’t have a way to adjust MR on the front, so I’m limited to just playing around with the rear end.

I'm sure your Motion Ratio is inverted from what I use (which is Spring Motion / Suspension Motion). In my world that would be a motion ratio of 0.8 going to 0.833. In your case the spring is going to move more for the same amount of suspension movement, and the difference is very small.

Try it -- there will only be three results -- better, worse or the same. It's your job to figure out which of those it is. If it's worse, then just put it back.

As David implied, it depends - ARBs are more a tuning aid unless you're getting into some of the more exotic designs.

Thanks Gord. Certainly nothing exotic going on with my amateur projects! My plan is to test a bunch of sway bar settings and find the LLTD that I’m happiest with. Then I’ll try to replicate the same LLTD by prioritizing the dampener motion ratio paired with the softest ARB setting that gives me the same LLTD value and see if I notice any difference in handling qualities. The result will likely be an imperceptible difference for someone like me, but it’ll be good experience. I’m sure as with my other suspension testing I’ll discover that the best course of action is to just do what the manufacturer suggested in the first place 😂. At least I should learn something along the way. Thanks for the help and input as always!