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Old 10-11-2009, 10:02 PM   #1
Davidss
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Member#: 27446
Join Date: Oct 2002
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Location: DFW
Default STI Wheel Spin?

So I normally race a STS prepped CRX, but last week it's engine popped. So today we raced my wife's STI. We had some serious issues with wheel spin and a weird jerky/vibration/bouncing. First off here is the car's setup:

2005 STI
Stage 2
Whiteline 24mm Rear Bar on Full Stiff
Fresh 245/17 Hankook RS2's
On VERY Grippy Concrete

-1 deg front camber
-2 deg rear camber
Zero Toe All Around

The issue is on corner exit under power it feels almost like the clutch is slipping, and sometimes the car jerks or even 'bucks'. So far from searching it sounds like my car may be lifting an inside rear wheel and all the power is spinning air...

1. Is this a common issue? Stock STI's spinning an inside rear tire with just a big rear swaybar?

2. Could my rear camber be making the problem worse? I would think that if the inside rear tire was getting light that much camber would make for a really small contact patch...

Any other ideas on what's wrong? Or how to fix this besides putting the stock rear bar back on?
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Old 10-11-2009, 10:22 PM   #2
subydude
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Join Date: Jan 2005
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Location: Columbia, SC
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2000 2.5 Auto-X RSTi
What's A Head Gasket?

Default

Quote:
Originally Posted by Davidss View Post
1. Is this a common issue? Stock STI's spinning an inside rear tire with just a big rear swaybar?

2. Could my rear camber be making the problem worse? I would think that if the inside rear tire was getting light that much camber would make for a really small contact patch...

Any other ideas on what's wrong? Or how to fix this besides putting the stock rear bar back on?
1. Yes. Read this: http://forums.nasioc.com/forums/show....php?t=1856697

2. It could be contributing, but the bar is probably doing more.

lots of suspension, clutch diffs, and several years of trial and error
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Old 10-11-2009, 10:25 PM   #3
nhat
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Location: 3MI Racing
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03 STi
hellaflunctional

Default

i've never experienced that when i was autoxing my 04 sti with rce yellows or jdm pinks, 255s, and the same WL rear bar set to full stiff so i don't understand how the inside rear wheel would lift with stock springs.

maybe it's a combination of the stock springs with the WL rear bar?
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Old 10-12-2009, 12:59 AM   #4
Splash
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It's the 24mm rear bar set to stiff with a stock front bar. Either stiffen the front, or soften the rear.
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Old 10-12-2009, 01:07 AM   #5
Davidss
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Default

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Originally Posted by nhat View Post
i've never experienced that when i was autoxing my 04 sti with rce yellows or jdm pinks, 255s, and the same WL rear bar set to full stiff so i don't understand how the inside rear wheel would lift with stock springs.

maybe it's a combination of the stock springs with the WL rear bar?
How much camber?
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Old 10-12-2009, 09:39 AM   #6
Calamity Jesus
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Quote:
Originally Posted by Splash View Post
It's the 24mm rear bar set to stiff with a stock front bar. Either stiffen the front, or soften the rear.
I'd recommend stiffening the front.



It's fun.. but it's slow. Once I added an even larger front sway, it went much faster and had traction for exiting corners.




Different car.. same concept.
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Old 10-12-2009, 02:54 PM   #7
STirish
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Aspen White

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*edit* please see my post below.

Subarus tend to pick up rear wheels when they are stiff or softly sprung. Some stiffen the front (given they already have stiff C/Os) to help keep the wheel down, but I've found the car looses steady state grip, and therefore speed, given how much rate is in the front vs. rear (stiff front bar + heavier springs in front vs. rear) of the car. That being said I tend to run more rate in the rear than the front.

With any of my STi's, '05 or '06, none of them have clunked or bounced funny exiting corners under power with any of the setups I have tried. From the pictures below you can see I have a bit of experience three wheeling on street tires.

From what you have described, I would personally be looking for mechanical issues. Broken mounts, diff problems, etc. It's possible you are seeing what the BSP or SM STis are seeing when they have tons of grip!? Seems unlikely though.

All pictures below are on corner entry while trail braking.

2006 STi with a Cobb rear bar on on full soft. Stock front bar:



2006 STi with 21mm Whiteline on full stiff. Cobb front bar:



Thanks,
Rob

Last edited by STirish; 10-12-2009 at 08:27 PM.
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Old 10-12-2009, 04:13 PM   #8
nhat
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Quote:
Originally Posted by Davidss View Post
How much camber?
-1.5* front and -1.7* rear.



that's with rce yellows and the WL 24mm rear bar set to full stiff.
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Old 10-12-2009, 05:22 PM   #9
STirish
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'06 STi
Aspen White

Default

A less scatter brained post than I had above. Being home sick has some time advantages.

The suspected problem of rear wheel lift at corner exit may be difficult to actually happen. Generally rear wheel lift for GC/GD Subarus happens on corner entry under braking. At that point your weight transfer is heavily set to the outside front wheel, taking weight off the rear. As the car settles into the corner the weight transfer front to rear balances a little more while running maintenance throttle. The rear wheel sets back down in steady state. On corner exit the steering wheel is being unwound while adding throttle (early throttle in the AWD car ) and the weight starts shifting to the rear of the car. With weight transfer to the rear it's very difficult to pick up a rear wheel. Generally it's a front inside wheel that can lift on corner exit. BMWs are well known for lifting front wheels on corner exit. See the sequence of corner shots below.






It is possible you may be spinning an inside wheel on corner exit, except for the fact there is tons of droop travel on the stock shocks. It is possible however. If spinning an inside front wheel is happening on corner exit, more rear spring rate would be in order or the ability to add rear compression or front rebound (not something you can do). I would look for broken mounts, diff issues, or the like first.

As a side note, adding a front bar to your softer camber lacking setup should help with front grip. My '05 STi ran JDM pinks with 24mm whitelines bars on full stiff all around. Great balance if not a touch loose ~-1F/-1.7R for camber and zero toe. It's probably not the rear camber causing your issue.

Last edited by STirish; 10-12-2009 at 05:28 PM.
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