Generically, most sway bar s run roughly +10%, +50%, +100% give or take.

The point to remember is the bars are in parallel with the springs in a turn and generally one would not want bars to provide more than half the total roll stiffness.

So 100% stiffer than oem might really be stiff enough to provide 50% of the total.
For example my old Q came with NO rear bar and 123 pound per inch [wheel rate] springs so my 20 mm rear bar adds 40 pounds per inch so 163/123= 32.5% increase in TOTAL rear stiffness.

You really have to know what the oem bar really is in pounds per inch to evaluate the true meaning of 50% or 100% stiffer.

The front oem bars are always too stiff and overload the front tires to create some safe understeer. It is often a mistake to stiffen the front bar.

Remember 3 adjustment holes allow 6 levels of adjustment.........no rule says you must use the same holes on both sides: 1 + 1,2,3 - 2 +1,2,3- 3+1,2,3.

10%, 35%, 50%, 60% 75%, 100% or there abouts.

 

So are you suggesting that if your car is lowered HKS RS in my case using soft/med setting is better?

 

Depends on the actual amount of spring stiffness.
Obviously with stiffer springs the bars contribute a lesser amount [%] to over all roll stiffness.

Many times you gain more with softer than oem front bars as the front bars come way too stiff from factory.

All about setting the ratio of stiffness equal to weight distribution ratio......for example a car with 54/46 weight ratio should have 54/46 springs and bars......then make the front bar stiffer by some safety percentage to build in some understeer for [rear tire] acceleration and wet weather.

Do not even approach a perfectly balanced spring/bar stiffness [as loaded with passengers/fuel] as you will be on the ragged edge of spinning out in dry conditions when you accelerate in a curve.

Many oem designs have the roll stiffness f70/r30.......due to a really stiff front bar..............increasing the rear bar by 100% [say 50>100 lb/in] can reduce the ratio to ~~60/40.

There is usually some slack in the FRONT bars mounting structure [rubber bushings] to allow lose coupling in the first inch of body roll [one wheel on a bump/pothole, etc] to reduce street harshness..........so the bar is actually stiffer than one would expect to make up for slack in next 2" of body roll.

Most systems are tuned for a 3" body roll at max G since shocks have only a max +-3.5" stroke. Gets complicated when you change springs.

 

That's a lot of really good advice, particularly about the stiffness of the OEM front bar. My last car was a Toyota Solara, which is FWD, and a lot of guys on one of the forums for that car are just hooked on getting stiffer front and rear sways for that car. With the stiffer front bar and the FWD platform, some of them learned some expensive lessons about severe understeer by sliding into telephone poles and other immovable objects. With the G's RWD platform, it's not quite so bad, but you still don't want to get too stiff with the front bar.

 

If I put my '05 350z suspension in my G sedan which lowers it 1 inch all around and the spring rate is the same as stock what would you recomend my stillen sway bars be set at?

 

I am always a fan of softer than oem front sway bars because the front tires are the limiting factor and less bar stiffness increases front traction.

 

I think the Stillen front bar on it's softest setting is supposed to be 7% firmer that stock. Start with that, along with a medium setting on the rear bar, and see how it works for you. That's the setting I had mine set at when I lowered the car about 1.5" all around with the Tein CS coilovers. I notice less body roll all around and things feel fairly balanced.

 

ok so basically it sounds like most people are leaning towards soft/med. thanks

 

Remember you can set the bar asymetrically: use one soft hole and one medium hole for an even finer range of adjustment.
You actually have 6 different stiffnesses in 3 adjustment holes.1,1;1,2,;1,3 then 2,2;2,3 then 3,3

Think of the progression as 5%>25%>50% PER SIDE.

10% >30% >50%>55% > 75%>100%.....+8lbs/in, +24 lb/in, +40 lb/in, +44 pound/in, +60 lb/in, +80 lb/in........................approximatation assumming 80 lb/in regular oem rear bar as measured at the wheel road interface.

The above is just an example as the real number at the road will depend on tire brand/inflation/size temperature etc.

If a professional race driver can feel 1 psi difference in tire pressure you should learn to feel 5-10 lbs [2-3%] per inch in rear roll stiffness difference.