Sway Bars: What's The Trade Off?

[wparsons]

Decrease or loss of independent suspension movement is the trade off with stiffer sway bars. If you go too stiff with the sway bars with too soft of a spring you'll still transfer weight to the outside wheel AND will lift the inside wheel so you could actually end up with less overall grip by running too stiff of sway bars all around.

Grippier tires and a proper performance alignment will get you gains for sure with less trade offs than stiffer sway bars.

[CSG Mike]

We use sways to fine tune understeer/oversteer bias. That being said, sways are a fine tuning tool, like alignment, that is often used to address handling problems, when in reality, the superior fix is in the static spring rates.

The CSG BRZ uses stock sways.

In relative order of effect on handling balance from largest to smallest:

Spring rates (and dampers, properly matched to the spring rates)
Sways
Alignment
Tire Pressure

You want to get the closest you can at the top, and then use each successive step to get closer to your desired balance.

[autobrz]

sway bars transfer weight from the inside tire to the outside tire affecting total grip. How much weight they transfer depends on how much the car rolls. I think this is the reason why sway bars make a car's handling inconsistent when surface condition changes. On a less grippy surface, the car will generate less body roll but depending on how big the sway bars are, the front and rear balance will change because of change in weight transfer to due change in body roll loading the sway bars. springs on the other hand, do not change the amount of weight transfer. To combat camber loss, it is probably better to add static camber and caster.

not sure if what I wrote makes any sense or if it's wrong, lol...

p.s. one thing I noticed on my last car is a big front sway bar made the front end push and killed the steering feel. stiffer springs made the front end grip better and increased steering feel. Both done without changing the rear suspension. It was macpherson struts too and camber challenged but the difference between springs vs sway bar was pretty significant.

[Captain Snooze]

Originally Posted by CSG Mike

when in reality, the superior fix is in the static spring rates.

I have read that increasing roll stiffness using sway bars is less harsh (read more comfortable) than increasing spring stiffness. I have also been told by a suspension shop ( I am taking this as a hypothesis because I have no other examples to back this up) that sway bars should provide a certain percentage of the total roll stiffness. (I cant remember what they said and it was a ball park figure.) So according to this hypothesis because I have increased the spring rate the sway bars should be upgraded as well.

Your thoughts?

[neurokinetik]

Originally Posted by celica73

Is your BRZ a race car? Does it only gets used on race tracks?

What "race cars" are you talking about, and what spring rates are they running? Most race cars I'm aware of are set up as soft as they can be. You need more spring when you can't maintain the tire contact patch. That happens when you have grippy tires causing too much body roll.

Also worth noting is that many of the race cars using stiffer springs do so for aerodynamic reasons. Any underbody aero is designed to work best at a specific ride height, and spring rates tend to be the minimum required to keep the car off the ground and allow the splitters, undertrays, and diffusers to work at optimum efficiency.

[ZDan]

Originally Posted by autobrz

sway bars transfer weight from the inside tire to the outside tire affecting total grip. How much weight they transfer depends on how much the car rolls.

Any time you are cornering, there is weight transfer equal to the weight of the car multiplied by cornering gs multiplied by c.g. height divided by track width. Cornering in an FR-S/BRZ at 1-g, weight transfer = 2950 lb. * 1 * 18"/60" = 885 lb., whatever you have for sways, and (pretty much) however much the body rolls.

[that_guy]

Originally Posted by ft_sjo

What problem are you trying to fix? What characteristic of the handling do you want to change?

Glad someone said it!

Sway bars are a tuning tool. You install them to compensate for something the car is doing, that you'd prefer it not too.

"Sway" is actually a good thing in cars. It allows the weight to transfer around the vehicle and load up the tires for grip. A tire with no weight on it will most definitely break loose. Vise versa, a tire with too much will do the same.

Sure, bigger sway bars make the car feel and drive different, but different isn't always better. I would love to see someone run a demanding track with and without sways, and even various combinations of stock/aftermarket sways in the front and rear to see the results. Until then, the butt dyno will always say better but this isn't always a good thing.

In autocross right now, I'm running KW V3's and the car is perfect after some delicate damper and alignment tuning. A co-worker of mine runs the same suspension, but with TRD sway bars. We can't sort his car out because it behaves so differently. It doesn't lean when it needs too and that's part of the problem we are having. So he needs to run less camber and a different profile for the dampers to achieve the same result of not having the stiffer bars in the first place.

Know what your getting into first before you expect parts to make a substantial difference in performance.

[Captain Snooze]

Originally Posted by that_guy

I would love to see someone run a demanding track with and without sways, and even various combinations of stock/aftermarket sways in the front and rear to see the results. Until then, the butt dyno will always say better but this isn't always a good thing.

But then you are comparing different total roll stiffness. I would have thought that a better test would be to remove sway bars but increase spring rate.

[Xauterus]

You have to be careful with a rear wheel drive car and too much rear anti roll bar. Because the two rear wheels are linked by the bar, a load on the outside tyre will load the inside tyre. With the car being rear wheel drive you will start to lose your power to the ground once the inside wheel comes off the ground.

I think you want the springs reasonably stiff with as little anti roll that will give you the handling you require. I think you want the rear to be as soft as possible in roll so the wheels are on the track. It is not a WRX that inherently understeers and hence needs massive rear anti roll.

Dont forget you can change the rear toe to change the oversteer, understeer.

[autobrz]

Originally Posted by ZDan

Any time you are cornering, there is weight transfer equal to the weight of the car multiplied by cornering gs multiplied by c.g. height divided by track width. Cornering in an FR-S/BRZ at 1-g, weight transfer = 2950 lb. * 1 * 18"/60" = 885 lb., whatever you have for sways, and (pretty much) however much the body rolls.

OK I see your point. Then what term would you use to describe the fact that the sway bar pushes the inside wheel up and at the same time pushes the outside wheel down with equal force. If the suspension setup is already at maximum grip, adding more sway bar will reduce grip because it unevenly distributes weight on the inside and outside tires.

[xwd]

Originally Posted by Xauterus

You have to be careful with a rear wheel drive car and too much rear anti roll bar. Because the two rear wheels are linked by the bar, a load on the outside tyre will load the inside tyre. With the car being rear wheel drive you will start to lose your power to the ground once the inside wheel comes off the ground.

I think you want the springs reasonably stiff with as little anti roll that will give you the handling you require. I think you want the rear to be as soft as possible in roll so the wheels are on the track. It is not a WRX that inherently understeers and hence needs massive rear anti roll.

Dont forget you can change the rear toe to change the oversteer, understeer.

Too stiff in the rear is definitely an issue in this car. If you upgrade the rear to something stiffer you can even run into issues going up driveways at an angle since it will keep the other tire off the ground. All of the STX autox guys end up using the stock rear and a stiffer front to help maintain camber. Phil at Element Tuning just removed his rear since on his time attack car he is running fairly high spring rates.

Upgrading bars is a less harsh way to add roll stiffness but with definite drawbacks.

[Captain Snooze]

Perhaps what I am wanting is not possible: an increase in cornering performance without making daily driving tedious/unpleasant.

[autobrz]

sure there are ways to increase cornering performance without giving up comfort. Get really sticky tires and run a ton of camber like the racers. 3.3 front 2.5 rear or something like that. May require you to lower the car or get control arms to achieve those numbers.

That sounds more expensive and complicated than what you're planning to do though.
Maybe as a compromise, you can do the stock class autocross setup which is a big front sway bar + sticky tires + more front camber + alignment to get the car to rotate.

[Captain Snooze]

Originally Posted by autobrz

That sounds more expensive and complicated than what you're planning to do though.
.

I have already fitted aftermarket dampers/springs + adjustable camber plates,upgraded front lca bushes, rear lca (spherical bearings), rear toe adjusters, wearing Kumho V700. The price of aftermarket roll bars seemed like a relatively inexpensive modification.