Stiff Front Sway Bar Thoughts

geeteezee

I was under the impression that our cars were more prone to oversteer.

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Spooler

Undertsteer is correct unless you have a Nismo. They are pretty darn neutral out of the box. The V1 Nismo's. I have never driven a V2 Nismo.

filip00

Actually not at all. Best example is if you try to do a slalom in slower/moderate speeds. The car will understeer quite a lot way before the rear will snap out. If you put a rear sway bar, suddently the nose feels pointy and precise and no more understeer. I was quite amazed at the difference it made, immediately reminded me of most sporty versions of bmw (saying this because I have most experience with them).

Hotrodz

It not to complicated...most cars these day are setup to understeer because when the average Joe or Jane make a mistake and takes a turn to hot the correction to it is hit the brakes. The Z is no different and do to having a staggered tire and wheel setup it is more exaggerated. The increased rubber, traction and power of the rear wheel will overcome the grip of the front wheels and tires. Have more front bar helps combat that condition. This why many, me included run square at the track and still have the biggest bar available up front.

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littlejuanito

This is precisely where I'm confused

Wouldn't this situation cause understeer and having a stiffer bar induce even MORE understeer?

Not saying you guys are wrong, just wanna know why is this different in the Z?

Hotrodz

No...think NASCAR! The setup causes the car to push because there is not enough grip in the front to hold the car in place so even though the wheels are turned the car goes straight. Oversteer occurs when the front of the car turns (has more grip or resistance) and the rear rotates around do to the loss of traction in the rear.

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littlejuanito

Great. Thanks Hotrodz

Hotrodz

Lol I was just trying to keep it simple. It is basic physics, weight, friction, force and power. Force=momentum and power=acceleration. I got a C in physics by the way so I'm no rocket scientist lol!

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cloudofevil

It also has to do with camber curve. If the camber curve can't keep up with the body roll then you need to reduce body roll. Plus excessive bodyroll is just harder to control.

MaysEffect

This is taken into consideration from factory. Thus the oem alignment specifications. Things start to change when you decrease or increase tire grip, IE larger tires, grippier' tires.

Reducing body roll in the form of a stiffer sway bar doesn't reduce camber curve however, in some cases of high load you may be increasing it. You will need to combine this with a higher spring rate to combat compression across the axle. Neither is a great option unless you increase tire traction and tire load.

and the melting pot of tuning begins

cloudofevil

Right, it reduces how far through the camber curve the suspension travels. Enough body roll and camber starts to increase.

MaysEffect

Agreed, but if you use a stiffer sway bar alone you are increasing the load on the outer tire. This is no better of a solution then allowing a higher level of camber gain, certainly if you already have a small amount of static camber (-1.5 degrees or less).

The tire sidewall is going to start to roll over more with the increased load and then you still end up sliding more. Most sway bars on the market increase the roll stiffness by over 20%, in some cases as much as 100%. This is most likely greater than going up a spring rate compared to the oem springs. At this point its really up to the driver how they manage tire heat. with increased roll stiffness you will be heating the outer tire significantly more.

SeeThruHead

I always come back to this thread when trying to understand sway bar stiffness on the Z.

I found this today that seems directly related to the conversation.


From the pages of High Performance Handling Handbook by Don Alexander:

"There are situations where increasing the stiffness of an anti-roll bar will have the opposite effect. Most stock vehicles have excessive understeer because it is easier to control and provides more stability for the average driver than a vehicle that oversteers. A big part of this comes from excessive body roll, which induces too much camber change, and a good portion of the front tire contact patches loses contact with the road.
In this instance, adding a stiffer front anti-roll bar, which would typically increase the extreme understeer, actually reduces the understeer by reducing the body roll-induced camber change. The front tires now stay in better contact with the road surface, creating more traction and reducing understeer."

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Averying

Good find!! I’m a nerd for learning more about suspension geometry and race car chassis setups so I love this stuff.

Found the post that explains this well. j-rho explains it better than me. See his post here: Auto-X street - no rear sway

It’s not that a front bar gives more grip… a stiffer bar actually asks MORE of the outside loaded tires… but the tire is kept in a better range of the camber curve which outweighs the increased load, and therefore more grip!

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AH370Z

I fitted a front whiteline sway bar with 2 settings, swift springs oem shocks oem 19" tyre sizes and Michelin Piot 4S tyres.

I asked whiteline how much stiffer over oem and soft is approx 30% and hard is 65% I tried the hard setting and the car just wanted to understeer too much. Simple test was perform quick U turn, hit the gas trying to spin the car around and it just understeered.

I simply cannot understand how some run the much stiffer bars up front 100-130% stiffer whatever it is. Just tells me majority simply do not drive the cars hard enough (which is fine) so all they are feeling is the stiffer setup and less roll, but if actually drove the car agressivly they would end up pushing.