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Discussion Starter #1
I know there's a ton of info on sway bar performance, technical specs on tinsel strength, lateral stability, etc...

(For reference, I drive an '05 ST with Eibach Pro Kit springs and Pro dampers, and a front tower bar.)

I've been looking into getting both front and rear Eibach sway bars (aka anti-roll bars) but have been thinking of doing them in stages.
The rear is really easy to do, and the front is... well... not AS easy lol. But here are my questions--

1) I've read that it's downright bad to ONLY upgrade the rear (in this case, going from a 20mm to a 25mm bar). Is this true?

2) I've even read on other car forums that it's dangerous to have a stiffer rear end. People talk about how the rear end wants to kick out and it's easier to lose control at higher speeds. Is any of THAT really true?

3) Has anyone actually upgraded the rear bar only, and left the front stock? Was there a benefit at all? What can I expect as far as changes in under/over steer characteristics?

4) Will I even feel any difference without both front and rear done? Should I just save up and do everything at once?

Thanks in advance everyone.
 

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I can speak to what I have done to my 05 st. First it's a dedicated scca race car, I have been running for a year. Front is set with camber plates, H&R coil overs and adjustable rears. Started with stock front bar and 25 mm rear. Moved to a 28 mm rear and then finally removed just the front bar. No high speed problems, much more comfortable for my style of driving, I also hav a quaife. I have been racing front drivers for a number of years and on the track, I tune with spring rate and no front bar..
 

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Focal Distortion
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well I added a rsb 21mm, to my 2010 and it made a huge difference! Now being that you have both front and rear stock, I really can't say, sorry
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Discussion Starter #4
Interesting.
My car is a daily driver. The most amount of spirited driving I do is up and down winding CA mountain roads.
So in your opinion, if I just upgrade the rear bar for now, I wouldn't see any negative, or unbalanced, handling affects?
 

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There's generally no downside to upgrading just the rear bar as long as you are reasonable with sizing.

msperber's comments are good but rememeber they are for a race car. Race rubber and smooth tracks can make a very big difference in suspension setup options. Going with big bars for street use can make the rear very loose especially on uneven pavement. Bumps in curves can make the rear end jump around alot rather than stay planted, but the same can happen with excessive spring rates or the lack of proper damping as well.

I always recommend that you do your spring and shock improvements first. The right spring rates can sometimes negate the need for sway bars or upgrading/increasing the size. If after you do the springs and shocks you find you still have too much roll or too much understeer for your tastes, then consider adding sway bars (if you don't have one) or increasing their size.

I went from the stock bar to an SVT bar on our ZX3 and there was a noticeable handling change. Understeer was reduced and the car handling became more neutral. This was the result of a 1mm increase but was also accompanied by the slightly stiffer spring rate increase and firmer shocks that came with the SVT suspension kit. On my RX7 rally car, I too removed the front bar and kept the stock rear bar to make the car more toss-able on dirt roads and the ability to induce oversteer with the gas pedal.
 

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Discussion Starter #6
There's generally no downside to upgrading just the rear bar as long as you are reasonable with sizing.

msperber's comments are good but rememeber they are for a race car. Race rubber and smooth tracks can make a very big difference in suspension setup options. Going with big bars for street use can make the rear very loose especially on uneven pavement. Bumps in curves can make the rear end jump around alot rather than stay planted, but the same can happen with excessive spring rates or the lack of proper damping as well.

I always recommend that you do your spring and shock improvements first. The right spring rates can sometimes negate the need for sway bars or upgrading/increasing the size. If after you do the springs and shocks you find you still have too much roll or too much understeer for your tastes, then consider adding sway bars (if you don't have one) or increasing their size.

I went from the stock bar to an SVT bar on our ZX3 and there was a noticeable handling change. Understeer was reduced and the car handling became more neutral. This was the result of a 1mm increase but was also accompanied by the slightly stiffer spring rate increase and firmer shocks that came with the SVT suspension kit. On my RX7 rally car, I too removed the front bar and kept the stock rear bar to make the car more toss-able on dirt roads and the ability to induce oversteer with the gas pedal.
Thanks for your comments. I have done a suspension overhaul. I never wanted coilovers or really firm "race" springs. Eibach Pro Kit springs dropped me 1.5" and those paired with Eibach dampers gave me really great "around town" drivability. But I do feel just a little more roll than I would like when I go on my weekend mountain runs. I'm sure if I had even firmer springs, I'd be happy, but it's just not what I want on a daily driver with horrible roads to contend with in town.
My car is in no way a race car, and the comfort factor is a big deal to me. So as long as doing one bar for now doesn't completely alter my car's handling characteristics, I think I'll probably go with the rear bar first, see how I like it, then figure out what to do next.
 

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Not sure if this is still true with the '05 but on my 2001 I ended up having the rear lower arm brake at the sway bar joint. I think this is a combination of running a large sway bar and a softer suspension ( had a SVT and current suspension). Have upgraded to the "newer" arm that is reinforced in this section. Just keep an eye on it.
 

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I upgraded to svt suspension kit (pre built struts), brakes. I also got a used svt sway set. I couldn't get the front off the crossmember, so I have a stock spi front bar (smallest), and installed the rear svt bar. I heard of the cracking issue and got the tubular weight jacker arms a former member was selling. I had to cut the bolts to remove the rear control arms because the adjustment bolts were seized and couldn't be adjusted.
I run a soft front bar, and svt rear bar. I like the improvement, though going in and out of drive ways you notice more rocking from the rear bar than front. It's been in for a year and a half to 2 and a half years, and I would say that there is nothing unsafe. It has improved handling, and while I still intend to upgrade the front bar, it's a would be nice, not gotta do period item....
Do the rear, it'll take you 15 minutes, go from there....
You've got a '05, so your arms probably have a second piece of sheet metal where the links attach (that's all the reinforcing is). If not, consider getting ones that do and keep assn eye on your current ones till you get some.

Good luck,
Happy motoring....
 

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You already have a 21mm front & a 20mm rear. So I'd go for the Eibach bar's= 22mm f & 25mm for the rear. For the front one, you'd need to drop the cradle down a little to rear & replace & then you need a alignment. Going froma 21 to a 22 doesn't seem that much, but your also adding poly bushings too. You will find your car is easier to rotate mid corner. A bigger rear bar also adds weight tranfer to the inside wheel too.
 

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I have an 05 ST (same color too!) and did the progress 22 rsb, it's been fine for me on the street. If I get around to doing a trackday with this car I'll likely wish I had more, but for driving around town and some twisty roads it's great. The extra 1 mm was noticeable.
 
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