What I've found is that the roll we get is pretty substantial until the car is lowered enough to physically limit it....but that also brings geometry issues along with it. A BIG FSB will limit roll no matter what height you are (within reason) and allow the (front) camber to stay in a more desirable area. The rear end likes very little camber because any roll that we end up with will put the outside tire out on it's edge and contribute to rotation. Naturally, you have to balance it with spring rates so you aren't wallowing around or even worse, lifting the inside front wheel (yes, it can happen in an Impreza). I prefer to run less bar in the back (or no bar) and very little camber to get my rotation without lifting a rear wheel and hurting forward bite on corner exit.

My FSP Brighton has a very neutral feel to it with low steering inputs. I've gotten it dialed to the point that if I want rotation, I simply add more steering input while keeping steady on the gas....or tap the brake just prior to turn-in. I can pretty much bring the tail around at will, but I have to remember that I don't have the power to pull me out of a slide if I let it go too far. I also have to make sure I know my arc going into a corner. Midcorner corrections to the inside get sketchy, but more often than not, I can get to the inside without instigating a drift. Daily driving the car helps me stay in-tune with the traits. I don't run bars at either end and developed this setup for 13" wheels. When we run the bigger 15's (275-35-15), we have to raise the car 1/2" and the extra grip is enough to roll it over more than I'd like. I added 1/2 degree of negative camber (about -1.5) in the rear to balance things out, but will be trying the stock 19mm bar up front again to see if I can limit the roll to where it was. I'm still learning the limits of the tires, as it is way higher than the 13" Hankooks. I'd love to try a set of 255-40-13 Hoosiers back to back with the 275-35-15 and gauge which is better overall for my setup.

Did I even come close to answering your question? he he he......

 

ill try its this sunday ill unbolt my rear bar

 

I've seen Jay's car at a few auto-x events, and my dad has even gotten a ride in the car, it's definitely capable!

Back to the orig. question, how big of a front bar are we talking about?

 

Jay, you delivered as usual. Thank you.

Sleepy, if you do please report back! I'm not familiar with your setup though and you haven't posted it in the autox setup thread.

n2x4, I had a Tribeca FSB in mind.

Looking through the autox setup thread I noticed that Omaha is also running a larger FSB and on RSB too, as of last year. It looks like I'm not the first person to think of this :lol:

 

ya its all in my member jurn. if its not raining i will def unbolt one run but its calling for like 50%. so i might not climb under the car in the rain we will see

 

I resisted the no bar setup for a long time....I dunno if I was stubbron, stupid or both....but the 1st year we ran Nationals at heartland park, our DSP car was so stiff, we had very little grip. Stupid of me for not even trying to disconnect the bars just to see what would happen.....With the FSp car, I just wanted to try something different. No bars works really good when the CG is low enough, as 13" wheels will allow.

I can definately see the benefits in a big Tribeca bar and small or no rear bar. You might have to address the differentials to take full advantage of the setup....but it's very much worth it.

 

I have the tribeca 25mm front bar on my 95L and a 20mm rear FHI bar and the handeling was negativly affected by this change. I had a stock 19mm front and the 20mm in the back and it was a dream. The 25mm in my opinion is just way to big and hurts grip. At my AutoX events I noticed a 3-4 sec difference from the 19mm bar and the 25mm. With the 19mm bar my speed into a sharp corner could be higher and i could maintain that speed. With the 25mm the car wanted to pull way outside, and wash out. However with the 25mm bar my slaom speed was higher.

 

im sorry to ask but im stupid . . what are the stock RS F/R sway bar sizes?? i know that one of ya have to know lol

 

19mm front and 13mm rear.

Archer, what is the rest of the setup? Camber up front, wheel/tire size, tire type, springs, ride height, etc. There's a reason the big bar works for some but not others.

 

Unbolt it either way (before it rains....like the night before) You want to be setup softer in the wet anyway.

 

Here are some pics illustrating my points earlier. These first two show big bars at both ends, but the camber is set so that any roll we get is going to keep the front tire at max grip, while letting the rear roll out onto it's edge. Note the wheel lift as well.


These are with no bars and small wheels. Note the car still doesn't roll over that much, but the front is standing nice and flat while the rear end stays pretty planted too.


Here's one showing the controllable oversteer during a corner exit (cooked tires played a roll in this pic too)....


And finally where we're at with alot of grip, still no bars, and still a little too high.

A couple pics from 2008 Nationals....browse the full album.
http://mageep.smugmug.com/photos/380107613_8JyR3-XL.jpg
http://mageep.smugmug.com/gallery/6014068_RyHmn#380129947_vocM2-X2-LB

 

Wow, this is an interesting thread. There is so much to think about when your setting up suspension! :rolleyes4

 

sucks on stock suspension i know that i tryed no rear bar and freakin sucked

 

That's because you didn't have a big front bar.

The fastest subie in my area runs 27-29mm front with 13mm rear... I'm fairly certain that at those rates, you could just lose the rear sway completely and not even notice...

-- Dave

 

What would be considered the minimum "Big Enough" FSB to get away with removing the RSB? I assume that a stiff enough spring is also needed?

 

I would say at least 26mm or 1" up front. Spring rates should be 400lb+ as well.

 

I'm bumping this again, but not to pester Jay about the huge FSB.



If I were to run street tires instead of r-compounds would 400+lb. springs still be needed with a large FSB and no RSB?

 

where do u get a front 27-29mm fsb?

 

Whiteline.

 

Would there be some interest in big(ger) front bars for the RS? I have a local who is making them for the STi and new WRX's. It would be nothing for me to hook up with him to make some giant bars for the GC too.....

 

depending on price. I love my tribeca bad but wouldnt mind something that actaully fits the car right and is larger then a 22mm

 

I'd be interested!

 

I'll visit my buddy soon. He's busy making bars for the S2k folks along with the new bodystyle WRX/STi folks.....but we can make a few before spring, I would imagine.

 

any update on this storm?

 

Is it a completely different setup for track racing/driving?

I was talking to a guy at the local subaru shop about an STI that they sponsor that was in the shop and he mentioned that the setup is a lot different on the track. On that STI they were running a large RSB but they put the stock STI FSB on because it handled better like that.

Seems completely against what is true in this thread, but then again its a completely different type of driving

 

I'll see how much bar stock he's got in the garage. I know he's making 32mm bars for the porky Imprezas as well as some hollow bars in various sizes.

Shoot me some diameters and I'll see what I can come up with.

 

I would say somewhere around a 27/28mm bar would be good.

 

This thread got me thinking. I might remove my rear strut tower bar first, and then try the OEM rear bar again (if needed). With the Tribeca bar in front, I have so much grip up front that the rear has trouble behaving in slaloms and quick transitions (have 20mm WRX bar in rear now). I only have the SPT wagon pink springs, which are in the 200# range, so "no rear bar" is probably out, but smaller sounds directionally correct.

 

This sounds rather backwards from what I've learned about suspension tuning. I could summarize what I think is happening, but instead could the well-informed shed some light on the general theory of running a setup like this?

i.e. camber/caster/toe, spring rates, damping, tire type, tire pressures, chassis alterations (braces/bushings/geometry changes), as well as driving techniques, etc. I am not trying to expose any secret recipes, but general methodology would help it make more sense.

 

I don't have time to write up a complete explanation right now. I'll try to remember to do it tonight.

It's solid thinking with a little bit of autocross specific bits that may go against the traditional grain.

 

I have been extremely happy with my 25mm front bar from Addco, but they only make a 24mm bar now. The car turns in nicely, but like said early, it does have a slight habit of washing out on corner exit... nothing that can't be overcome though. Keep in mind, this is on street tires too.... so I am kind of the lone wolf compared to the super fast DSP/FSP guys. Clearence is pretty tight with the 25mm bar, but a 27mm solid should be able to fit with the right bends, etc...

For what it's worth, I am on 8k/6k coils with 25mm front bar and 20mm rear bar, and stock bushings ( for now at least ). I am planning on lowering the car quite a bit over the holidays and going with a better alignment, so we will see how this works out next season.

 

I heard to win one of the rally championships subaru took off the FSB to win by increasing oversteer...think its true?