Auto-X street - no rear sway
 

So, given our cars tend to understeer, I was contemplating pulling the rear sway bar to see how it would drive. I figure it might actually work out...especially after I put wider rubber on the car.

Anyone try this out yet?

I'm no expert, but I don't think removing suspension bits is a good way to address understeer. There are better ways. I think a stiffer front sway bar would be one option. I'm sure some experts will chime in shortly.

Disconnecting the rear would have the opposite effect from what you want to do.

For SCAA Autox street class I suggest you leave the rear bar alone and get the stiffest front bar you can. Off the shelf that is the Hotchkis. You will find this opinion throughout the forums by searching.

although it doesnt make sense because a stiffer front bar = more understeer bias.

Sent from my HTCONE using Tapatalk

Generally I thought a stiffer front bar will induce more oversteer. I could be wrong though.

In terms of unbolting sway bars - plenty of guys at AutoX do it.

Here is a quick rule of thumb document - according to the accepted wisdom, stiffer front bar = reduced oversteer / increased understeer.

A lot of the track rats here are running a big front bar and the stock rear bar. Even me with my OVER square set up. :icon14:

It should be noted that for SCCA Street class legality, unbolting the rear sway counts as modifying the sway bar from OEM. Since you can only "modify" one sway bar, that would be the one modification so then you would have to run the stock front bar. The general consensus is that a stiffer front bar is the way to go in Street class.

As I've said before, with the stock suspension, there is really nothing you can do to make the car stop understeering steady state, that's just how it is.

Don't you typically remove the rear bar when you have high spring rates? Please let me know if Im wrong as I would like to try it too. I think a member here removed his rear bar and he said the car was more squirly.

The general guideline docs are based off the standard cause:effect relationships in tuning. However in some cases second-order effects can trump the primary effect.

In general stiffening a front swaybar will make a car understeer more. However, in the case of a car with poor front static and dynamic geometry (camber) - it can have the opposite effect. If the stiff bar keeps the car from rolling as much, it may mean the car loses less camber and the outside front tire has a happier resulting contact patch at terminal roll. Net result, the car may push less even though that outside front tire is being asked to do more via the primary effect of the swaybar.

I call this the Subaru effect because they all have crummy front geometry but the Z exhibits it also due to insufficient front camber. In my (admittedly limited) experience the car pushed less and less the bigger I went in front bar - with the other benefits of less inside wheelspin and better transitional (slalom) behavior.

Really wouldn't recommend pulling the rear bar on a stock car. The car is already so soft, eliminating a bunch of roll stiffness is going to make it worse, and worsen the resulting geometry in front.

I run stiff front bar oe rear. People who run high rates run no rear bar to allow it to be more independent.

Great input, thanks all. To address a couple point above.

Correct, due to SCCA street rules I would have to leave the front bar alone.

I also understand that conventional wisdom would tell me to just go with a stiffer front bar. However as I have read on multiple threads discussing this that adding wider tires has a tendency to amplify our cars understeering nature in stock guise.

Then comes the crazy idea to compensate by chucking the rear bar and thus make the car more oversteery...to achieve a more neutral balance in steady state steering. However then I am left wondering does the car become horrible for fast transitions like slaloms.

Crazy theory I know...but since this is so easy to try I assumed that someone had to have done so already...maybe not.

Softening or removing the rear bar will make the car understeer more as a primary effect, as it is softening rear roll stiffness in relation to the front. I would say it will also make it understeer more as a secondary effect, because the rear has good geometry and will still maintain great camber even with the extra roll, while the extra roll is going to make the camber situation up front even worse. Unless the plan is to intentionally try to run the rear on the bumpstops or something, but that sounds like a recipe for an unpredictable disaster.

I ran my car at a practice on RS3's with stock bars and upgraded shocks - it was terrible! So soft, it felt just awful. Last thing I would want to do is make it even softer.

I run a Hotchkis front and no rear. When going from the Hotchkis rear at full soft to none, I feel the car rolling a bit more, BUT, I can definitely put more power down through the turns without the back kicking out

Stock spring rates?

Have to agree with everyone here, more rear bar is not what you want. that is not the reason you are getting understeer. On OEM springs/bar the understeer is coming from sag and compounded by body roll. If you are on a budget, grab a set of swift spec-r's and a stillen front bar.

Umm, actually...im not asking if I should run more rear bar. I am asking if running NO rear bar at all might be a viable option to address understeer.

It's not really about budget either, more about applying non-conventional tactics to solve the problem within confines of competition rules.

As a general set of rules, whichever end is made stiffer, the less it will tend to grip and the more it will tend to slip; whichever end is heavier will tend to shift weight around more, and thus come loose; whichever end has poorer grip will tend to break traction.

In theory, to induce oversteer, all else remaining unchanged, you would want to run a stiffer bar in the rear, not remove it.

It gets trickier as you brace various sections, play with spring rates, tire camber, etc, but my guess is you'll want it as neutral as possible with just enough oversteer to suit your skill level.

All that said, if you touch nothing else on the car, but brace the hell out of the rear (e.g., with a stiffer anti-sway), it will be more likely to break traction on a turn.

Of course, you want it to be predictable and controllable, so that will depend on your skill, comfort, and familiarity with whichever course you are running. Just enough oversteer for one turn can be catastrophic for another depending on skill... dial in with caution.

Best thing to do if you are really serious is stick with OEM settings and get good with that -- FR cars tend to be a bit oversteer biased anyway (its pretty easy to break the rear tires loose on the Z), even though road cars tend to to be tuned from the factory to lean towards understeer.

If you can get the nose to tuck in consistently and controllably now, but feel you can handle more turn-in, go with a stiffer rear bar, ideally one that is adjustable.

Again, me personally, I like it as neutral as possible, with just a touch of oversteer, but my skills are modest.

On that note, I've previous set up FF's to rotate -- FF's are much more biased towards understeer, but it can be done if you brace the hell out of the right sections.

Do not take the bar off on a street class car. Period.

Ha! A very direct answer. I can appreciate that.

Sorry I read it correctly and typed it wrong.

If you are 100% OEM, definitely I do not recommend removing rear bar. Our rear OEM springs are too soft as it is.

If you want a quick decent upgrade though for not a lot of money I would still recommend the same spec-r's and the stillen bars. I would recommend adding one bar at a time just to see what it does. Start with the front full stiff +OEM rear. Then just disconnect one of the end links on the rear bar. Then try the stillen full soft...