WRX understeer

[Nige]

I have a 54 plate (UK) WRX & as bloody good as it is it really does have more understeer than I like.
It's got Potenza tyres on. Is it the tyres or the 4wd system pushing the nose wide on even slow bends?

BTW, I love the car & think as a work car & fun car you cant get better!

Nige

--
Subaru WRX (The Bitch)

Series 3 Landrover 88" (Albert)

"If you tolerate this then your children will be next"

 

[Carl 1 Lucky Texan]

For a lot of info on issues like this, some of the performance oriented
sites like www.nasioc.com are great.

In general, you can rotate better by installing a heavier rear anti-sway
bar, maybe a whiteline anti lift kit (ALK) possibly some camber plates
up front, and play with tire pressures. Others here will have more
experience/ideas too I'm sure.

Carl
1 Lucky Texan

 

[Nige]

For a lot of info on issues like this, some of the performance
oriented sites like www.nasioc.com are great.

In general, you can rotate better by installing a heavier rear
anti-sway bar, maybe a whiteline anti lift kit (ALK) possibly some
camber plates up front, and play with tire pressures. Others here
will have more experience/ideas too I'm sure.

Carl
1 Lucky Texan

Cheers matey!

 

[Mike]

My WRX did the same thing new, and had a lot of body roll. Per
newsgroup suggestion, I went and put new end-links front and rear (the kit
was about $125) and the anti-lift kit ($100) up front --White-line now makes
a "comfort" version that stiffens up the front but provides less road noise,
I wish I'd gotten that one. All that jazz, seemed to solve my handling
issues straight-away. A sway bar might be your next option. Also, while
the car is on the jackstands, it's a good time to slip in a Kartboy shifter
bushing set to get that slop out of the manual tranny. For $30 and 12
minutes of labor it's a good deal and the right time.

Mike

 

[dr.benway]

I ran 34 psi in the tyres and the problem went away..

 

[CompUser]

I have a 54 plate (UK) WRX & as bloody good as it is it really does have more understeer than I like.
It's got Potenza tyres on. Is it the tyres or the 4wd system pushing the nose wide on even slow bends?

If the Potenzas are RE-92s, that's part of it.
Get some stiffer sidewall tires on it and you'll
find a big change; you can decide after that if
you want more.

 

[Subie25l]

You can fix it a bit by changing the tyre pressures and the alignment. ie
less toe-in and maybe even some toe-out.

Search through the forums at http://www.mrtrally.com.au/forums/ and you will
find a lot of info on the subject.

Also the http://www.whiteline.com.au/ web site has a lot of info on WRX's
and alignment. They are also trying to sell their product too. They are
however very helpfull and very active on the MRT forums.

 

[David Betts]

I have a 54 plate (UK) WRX & as bloody good as it is it really does have more understeer than I like.
It's got Potenza tyres on. Is it the tyres or the 4wd system pushing the nose wide on even slow bends?

Pretty much all awd cars understeer. You can counter it with changes
to tyre pressures, different choice of tyres or suspension mods, but
it will always be there somewhere, depending on your driving style.

I assume you are experiencing the understeer in some sort of track day
or competition use. If you are experiencing it in everyday driving
conditions on normal roads then you are turning in to corners at far
too high a speed.. Slow in, fast out is the safe way to drive rapidly
on normal roads and also makes the best of the awd's ability to get
the power down early out of bends.

David Betts
(e-mail address removed)

 

[Danny Russell]

My WRX did the same thing new, and had a lot of body roll. Per
newsgroup suggestion, I went and put new end-links front and rear (the kit
was about $125) and the anti-lift kit ($100) up front --White-line now makes
a "comfort" version that stiffens up the front but provides less road noise,
I wish I'd gotten that one. All that jazz, seemed to solve my handling
issues straight-away. A sway bar might be your next option. Also, while
the car is on the jackstands, it's a good time to slip in a Kartboy shifter
bushing set to get that slop out of the manual tranny. For $30 and 12
minutes of labor it's a good deal and the right time.

Mike

Mike, did you install the anti-lift kit yourself, or have someone else do it? -Danny

 

[Mike]

Did it myself... it was the by far the most difficult part. You need a
lift with a lot of room, jackstands won't cut it. Then you need a big
breaker bar because the bolts are at a million foot-pounds. The reason you
need such vertical space is because you have to literally pry the front end
apart to fit the old pieces out and then the new pieces (plus additional
spacers!) in. I did it at an auto hobby shop and it was a pain. Little
room and lots of tensions/toques.

When all was said and done I had the alignment redone.

Mike

 

[Danny Russell]

Did it myself... it was the by far the most difficult part. You need a
lift with a lot of room, jackstands won't cut it. Then you need a big
breaker bar because the bolts are at a million foot-pounds. The reason you
need such vertical space is because you have to literally pry the front end
apart to fit the old pieces out and then the new pieces (plus additional
spacers!) in. I did it at an auto hobby shop and it was a pain. Little
room and lots of tensions/toques.

When all was said and done I had the alignment redone.

Mike

Thanks Mike. I have a set of the "comfort" ones on the way, I guess I'll pay someone to put 'em in
for me.

Are there any downsides to the geometry change? I'm assuming that Subaru chose the factory specs
for a reason. Unless they just deliberately chose a less aggressive steering characteristic from
the factory (read: idiot-proof)? -Danny

 

[Mike]

Danny-
That I cannot say why Subaru chose to make things "less" rather than "more"
up front. I have noticed that it drives a lot more responsive and that it
is slightly stiffer (and in my case more road noise). All of these factors
may have allowed Subaru to conclude that they would save that type of tuning
for the more aggressive STi community. Of course, I cannot stress enough
how much better the rear endlinks are (instead of those shoddy plastic bits)
and they are easy to do alone at home, weight-on-wheels. The kartboy
shifter bushings, although unrelated to the handling, are awesome; I plan to
go w/ a factory short-shift kit very soon, too. Makes my WRX a nice
package, and like I alluded to earlier, it was easy to do all this stuff at
the same time with relative economy.

My next enterprise, albeit miles away, will be to lose the Potenza rubbers
which I have not been fond of since day one.

Mike

 

[Mike]

Downside?? Might be that perhaps you'll like your car that much more and
drive it that much harder thus reducing mileage and tread wear. All that,
of course, should be offset by your ear-to-ear grin and wonderful love for
driving!

 

[Danny Russell]

Danny-
That I cannot say why Subaru chose to make things "less" rather than "more"
up front. I have noticed that it drives a lot more responsive and that it
is slightly stiffer (and in my case more road noise). All of these factors
may have allowed Subaru to conclude that they would save that type of tuning
for the more aggressive STi community. Of course, I cannot stress enough
how much better the rear endlinks are (instead of those shoddy plastic bits)
and they are easy to do alone at home, weight-on-wheels. The kartboy
shifter bushings, although unrelated to the handling, are awesome; I plan to
go w/ a factory short-shift kit very soon, too. Makes my WRX a nice
package, and like I alluded to earlier, it was easy to do all this stuff at
the same time with relative economy.

My next enterprise, albeit miles away, will be to lose the Potenza rubbers
which I have not been fond of since day one.

Thanks Mike. I own 2 Imprezas, an '02 (GGA) OBS with suspension mods, and a recently accquired '00
(GF8) OBS with no mods yet. I'm putting the ant-lift kit on this one.

Once you get the more aggressive rubber on your car you might decide to make some more tweeks to
your suspension setup because the dynamics change and the limits (and consequences) get a lot
higher.

My 'O2 came with the RE-92's which took me all of 12k miles to grind down with a 20mm rear sway and
urethane end-links in the rear. Once I put on RE-950's, I decided to go back to the soft rear
endlinks (I kept the 20mm bar) but stepped up to stiffer urethane end-links in the front.

I did it because with the grabbier rubber, the car had a tendency to snap-oversteer at the EXIT of a
corner as it hooked back up. Essentially the end of the car with more compliance in the roll
components (front) will tend to hook up first at the exit as the chassis unloads and whip the rear
around. Ungraceful and unsafe.

With setup the other way, you can still get a hair-raising slip angle going (with the large rear
bar), but reel it back-in gracefully at the exit. It's tough to explain.

 

[S]

Hi Nige, All!

I have a 54 plate (UK) WRX & as bloody good as it is it really does have more understeer than I like.
It's got Potenza tyres on. Is it the tyres or the 4wd system pushing the nose wide on even slow bends?

First of all, replace the RE92's; almost anything you can put on is
better. I like the Kumho MX, but they wear quickly.
IMO, the most effective single mod to fight the notorious WRX
understeer issue is the anti-lift kit. And yes, it _is_ a pain to
install; I can't even imagine trying to do it without the car up on a
hoist.
Other things that will help: Set the front camber adjusters to max
negative. Install "crash bolts" for more (1.5-2 degrees is probably
about right for "spirited" street use), and/or to get negative camber
at the rear. Set the front toe as close to 0 as you can get it (I run
mine at ~2mm _out_ for autocross), and the rear 0-2mm in. Often the
factory alignment is shockingly bad, so that probably should to be
checked anyway. Run a larger rear bar. The STi struts are
significantly stiffer than stock, and lower the car a touch, all of
which helps. A good coil-over kit might be a better bet, but I don't
have any direct experiences with these; replacing the stock struts
with STi's made a significant, if rather costly difference on my '02
car.
Realize that anything you do in this direction (except for the tires)
will make the car harsher riding on "normal" (ie bumpy, rutty,
pot-holed, fill-in-the-blank) roads, and will increase tire wear. Of
course if you are driving the car hard enough to get the front end to
push, tire wear probably isn't a huge concern for you ;-)
Hope this helps.

ByeBye! S.

Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101