How Anti-Roll Bar/Sway Bar Tuning Works

Today we look at how anti roll bar (or sway bar) tuning works, and how you should be tuning your anti roll bars to solve handling issues. Basically, stiffening a roll bar (sway bar) decreases grip on that axle, but also increases it's roll frequency.

Probably one of the more comprehensive videos on how do anti roll bars work on youtube.

[leonwurr]

You should do a video on roll bar tuning, and how the roll of the chassis could be used as a way to increase grip on transient regimes (by slowing down the weight transfer). The common sense, for people who do not understand the transient regimes very well, is to think the chassis roll is generally a bad thing, which is not the case unless aero comes to place. Also, a lot of books and people state that when designing a suspension you should always look for fast responses, but I'm not really convinced that a faster responding car, i.e. stiffer roll bars instead of no roll bars, is faster than a slower responding car, i.e. soft roll bars and a lot of body roll.

[danhermann]

the most clear way of explaining why anti roll bar affect under/over steer the way it does I've heard. you should replace the term friction on 0:25 on wards with the term slip angle coefficient to be more accurate with the physics of handling.

[fail_fast]

Great video Kyle, keep em coming. I love when you relate abstract concepts like ride frequency to real life situations. I can't tell you how many coefficients I've calculated from Milliken's equations which I don't truly understand what they are or how they relate to real life situations.

[crtmojo]

My understanding after the video is; It picks up the other tire to move some of the load over to the inside. Its a slight weight shift as it forces the car to squat down in the corners. You should feel more upright as you corner.

[snidewhips]

the condition you described of the rear feeling skittish is something i experience in my rally car, long wheel base, 8 inches of front and rear useable travel, its a rwd platform and have been considering tuning a rear sway bar to level the rear on corner exit and even the bump characteristics of the rear tow, its set in and at full squat ends up slightly out, with the rear leaning a little more given no sway bar i thing the skittishness comes from toe out on the load side and toe in on the light side, picture and vidoes don't show a great difference given the inboard spring design exactly like bmw;s at 308 lb per inch its fairly stiff, considering going outboard coil over to have a more predictable and usable sweep of travel given i'm using factory control arm components. thanks for the vids i find your info very informative and technically sound. Cheers

[seetllee]

Amazing explanation about the roll frequency subject. Would you have any literature regarding the transient responsiveness of the vehicle related to the roll frequency? I have a doubt. Seems that increasing the rear roll frequency would compensate the timing of the grip loss on both axis. But, once the forces are stablished and the car is on the steady state curve, a higher roll frequency would mean stiffer roll rate, which would lead to bigger weight transfer on the rear, leading the car to an oversteer. So would it be a tradeoff? Better transient performance over steady state performance? I think a better way to solve this would be softneing the low speed dampening of the front axis, or stiffening on the rear axis. So the responsiveness of both axis would be alike and wouldn't have to sacrifice the neutral balance (if it is desired).

[almightyalan]

Soon as i heard "yaw" my brain said "Lil pump ooo lil pump yaw"...

[TunesByTanzil]

Learnt a lot man, very well explained and easy to follow! Glad I watched :) Hi from Australia too hehe

[iTzadde]

That explains my 98WRX tendency to oversteer. I installed a Whiteline sway bar on the medium setting in the rear. It feels great but now I don't dare to put it on the hard setting until I have a front sway bar aswell.

[christopherdw]

A 100% Straight forward video delivery for the noobs fresh outta the UNO idiot students. Excellent job mate. Now maybe I won't see em in the ditch anymore.

[LetoDeWirre]

I think i finally understood what is wrong with those graphs that starts at 4:44.
This graphs shows performance of car with chassis torshional rigidity close to zero and explains why you want to make your chassis as stiff as you can.
Or i should ask you to advice me anoter bunch of books, because the one i have read ("How to make your car handle" by Fred Puhn) mensioned suspenshion frequency only in relation to ride quality.

[h.mushmann]

That there was a lot of information about vehicle handling characteristics in that brief explanation. I usually reference static loading since the math is easier, though it is still just a reference. Ultimately the specifics are still dependent on feel which requires real world testing, a max and min must be determined by the driver. More data allows for better decisions.

Personally, I slow roll to increase response with high rear damping. This makes the rear gradually lose grip and easier to drive when over loaded. There is a tendency for the rear to snap loose when under dampened which is not good when average human reaction time is 0.2 seconds. But there must be some compromise if the track is bumpy.

[singleturbosupra]

Nice video. I'll have to look up the roll frequency. Didn't really quite understand it's effects on handling. First time I've heard that word.

[stinkbra]

~what he's saying~
higher REAR roll bar stiffness=
*Corner entry UNDERSTEER (front response too low compared to rear)
*and mid corner OVERSTEER (common knowledge)

Most people think they have understeer (mid corner) issues when they really have front RESPONSE issues

[pnewhook]

This video is helping me understand how relative stiffness of front and rear ARB affect the balance of a car, but I'm not quite there. Around 2:55 you point out that if the front ARB is disconnected the rear ARB has to absorb all the weight transfer. But why doesn't the weight transfer of the ARB lead to a higher combined coefficient of friction at the rear? Let's say you're in a right hand turn with a front ARB disconnected. The left side tires will have a higher load. But on the rear axle some of the load is transfered to the right side through the ARB, and both tires are closer to their optimal grip. Why doesn't the rear have higher net grip?

[grantlauzon]

We need a twisting shock for anti-rollbars. Or maybe shock that links left and right pressure but only dampens the roll mother instead of vertical.

[BrandonKent]

I have a question I want a little input on. For a WRX, with 59-41 weight distribution, would you remove the 35lb spare tire and tools from the bottom of the rear trunk? or are the weight distribution properties going to outweigh the total weight change

[DeaShoost]

Thanks man, Seriously thank you. all your videos are very informative and will help me and my friends alot!

[iyadkamhiyeh]

I am a bit confused, ARB limit body roll and thus limit weight transfer, at the same time I have heard on multiple occasions ARB increase weight transfer

[blackstonegarage]

great video 👍 but how do you know how stiff a sway bar is too stiff?