Sway Bars: What's The Trade Off?
 

I have upgraded suspension which includes 6k springs front and rear. I do not want stiffer springs as this is a dd but I am wondering if sway bars may be a benefit for track work. I am considering RCE sway bars front and rear. Everything's a compromise. I know that but I don't know what the trade off is if stiffer sway bars are fitted. I appreciate that the ride will be slightly stiffer when hitting bumps on one side but anything else I should know?

I'm not sure if you would call this a trade off, but the stiffness of the front/rear sway bars will change your car's tendency to understeer/oversteer.

I literally just got done installing a set of RCE sway bars on my fr-s this evening. Before the sway bars I just had Swift fr-s springs and SPC LCAs which was a very close to stock setup as far as oversteer is concerned. After the RCE sway bars the car feels very different. On the same turn at the same speed, I'm getting a bit less oversteer and the car feels more controlled or balanced. The RCE sway bars are a very nice quality product. Highly recommended.

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

I personally found the car far too under-steer'y for me and not a very responsive turn-in (from what i'm used to), so I tried a couple of different rear bars and settled for a 16mm. An 18 unbalanced the car too much.

For track-only use i'd probably go with the 18 up back but increase the front one appropriately to maintain balance. The 18 rear on its own created a little initial understeer on turn (inability to transfer weight quickly enough due to stiffness) and then mid-turn the balance would change as the weight comes off the rear axle. Not confidence-inspiring.

I do not want to change the steering characteristics of the car hence (possibly) upgrading the front and rear sway bars. I am wanting to be able to corner faster. My understanding (probably incorrect) is by increasing the roll stiffness the the car will be traveling quicker for a given amount of roll due to the tyres being kept on their optimum contact patch for longer. That is, there is more resistance to camber change.

RCE sway bars are,from what I have read, of similar increase in stiffness front and rear plus they are both 2 position adjustable to fine tune the steering. So I corner flatter and (hopefully) faster and the steering is similar to how it is now but what's the down side?

If you want to corner quicker then you need to reduce the undesirable characteristic, either understeer or oversteer. Change the appropriate bar (bigger on rear to reduce understeer, bigger on front to reduce oversteer).

If your vehicle oversteers in a static circle then something pretty wrong with it.

I have to disagree with you there. If one increases the roll stiffness one can corner quicker. Hence race cars using very high rate springs. I can corner faster now than with the standard springs. I like the way my car steers now; I don't feel there are any "undesirable characteristics".

No worries. I'll give you the answer you're looking for; there are no trade-offs. Fit the sway bars!

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.

Sway bars, just like springs, are tuning tools. They can be used for good, or bad. The first step is actually knowing when you need them and why. Start with books by Smith and Puhn.

Scott

Then why are you changing the ARB's? They are mainly used to dial out over/understeer. If you feel that yours is in perfect balance then try other things to go round corners quicker.

I somehow think you're missing the point, what is stopping you "going round corners quickly"? Is the front starting to wash out or is the back stepping out on you?

But I thought this was the issue I was having.

Are you saying there is no benefit to be had by increasing the roll stiffness equally front and rear utilising anti roll bars?

No
Such as? As I have stated it is a daily driver so I do not want to compromise too much by fitting stiffer springs.
Ummmm.... I have already stated that I like the steering on my car the way it is.

I was under the impression that to to corner faster one needed to reduce roll.

I bet some serious race cars do have softer springs. There are too many variables at play to make strict generalizations. Those cars also run on smooth tracks and don't have holes in the road to deal with.

Did I miss the post where you mentioned excessive body roll due to excessively sticky tires? If so, I apologize. Not all body roll is bad. How well does a shopping cart corner? It's got stiff suspension and no body roll.

How much camber do you have?, Caster? Toe? Lots of variables. Larger sway bars probably will make you happy, but it's just a tuning tool. Most likely, it will also change the way your car does some things. You really won't know until you try.

Very well !! you should see me drifting from aisle to aisle :burnrubber:

P.S: just dont put the milk and kitty litter in the back !

Increasing roll stiffness will help you access more grip from your tires by reducing camber change. However, the trade off is that the plateu before the tires lose grip becopmes narrower.

This is pretty much a truth for all suspension upgrades. The more you tune for ultimate grip, the more of a knife edge you need to balance on before you start to slide.

Increasing roll stiffness also effectively increases spring rates when traveling over uneven pavement. If one side hits a bump, rather than absorb that impact by allowing wheel travel, the entire car will shift.

Anti-roll bars are essentially springs connecting the two sides of the suspension.