Stiff Front Sway Bar Thoughts

littlejuanito

Seems that the general consensus on running a stiffer front bar is that it will induce understeer but, why is the 370z the exception and more bar is preferred?

Can someone explain that to me. thanks.

MaysEffect

The Z is not the only exception. Almost every car with a greater front weight bias has a larger front bar. The wrong information has been spread over the past decade that the rear bar should be enlarged for a plethora of wrong reasons. In reality the only reason the bars should be increased is if you have a significant increase in torque or increase in weight and or spring rate.

Most cars understeer from either having too much weight on the nose, or not enough at speed, this is why a 50/50 weight balance is ideal or slightly rearward (48f/52r). Under braking and lateral forces, weight shifts forward and outward increasing load on the front tires. Too much load and you overload the tires and lose traction, too little and the tires won't grip. This balancing act is the most critical aspect of design.

The Z has more weight on the front axle, no where near the levels of a Subaru or VW. But combined with smaller tires, you get a loss of traction from tire overload. There isn't anything funky about the suspension design or alignment that would cause additional understeer.

Increasing sway bar size is rather compromising unless you're increasing the spring rate or the amount of lateral load (increased g forces from bigger, stickier tires). Adding a larger bar with the same factory tires will just increase the load on the outter tire and reduce the contact patch on the inner tire. This is no bueno, thus the plethora of complaints of understeer.

Adding a larger front bar will reduce roll as intended with increased lateral load or additional weight (downforce). Increasing the rear bar causes a cross weighting effect that will transfer additional load to the inner front wheel, sharpening steering response and tire grip. The downside being increased instability and increased load on the outter rear tire. The trade offs are vast if you aren't actually increasing tire grip and load capacity.

filip00

This, I think is the crucial thing to consider when upgrading sway bars. If you have a Z with a staggered setup, everything stock, car will be prone to understeer, that's how it's setup. To reduce it, you could either go with a square setup which will definitely help with the understeer, or you could stiffen up the rear ARB, which will do just as you said - cross weighting effect, transferring the load from the read outer wheel to the inner front wheel, where all of a sudden, most of the understeer is just completely gone.

Also, driving a simulator nearly daily, I fiddled around with various setups and if there isn't any change to the spring rates and dampers, if you leave everything stock, and if the car is understeer prone, the easiest way to remedy it quickly is to stiffen the rear ARB.

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.

Rusty

Hotchkiss sway bar on the front. If you are square. You can eliminate the rear bar. If stagger, use a rear bar.

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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).